Ilex rotunda, Ilex crenata, Ilex serrata, and Ilex serrata all belong to the Ilex genus of the family Aquifoliaceae. They not only grow in evergreen broad-leaved forests but are also frequently seen planted in parks and gardens, making them extremely familiar and common evergreen trees in Japan. Because they all share thick leaves and beautiful red fruits, distinguishing them can often be difficult. You can generally distinguish them by carefully observing the leaves, but checking the flowers and fruits will give you a more definitive answer. This article will explain the classification and morphology of the Ilex genus.

What are Ilex rotunda, Ilex crenata, Ilex serrata, and Ilex serrata?

Ilex rotunda, also known as Kurogane-mochi or Kurogane-mochi, is an evergreen tree that grows in warm temperate hilly broad-leaved forests. It is distributed in Honshu (Kanto region, west of Fukui Prefecture), Shikoku, Kyushu, and the Ryukyu Islands in Japan; as well as in Korea, southeastern China, Taiwan, Vietnam, and Laos.

Ilex integra, also known as the Japanese holly (mochi tree or holly tree), is an evergreen tree that grows in broad-leaved evergreen forests and is distributed in Honshu (west of the southern Tohoku region), Shikoku, Kyushu, and the Ryukyu Islands in Japan; as well as in Korea, southeastern China, and Taiwan.

Ilex pedunculosa, also known as winter holly, is an evergreen tree distributed in Honshu (west of Niigata Prefecture and the Kanto region), Shikoku, Kyushu, and Yakushima in Japan; as well as in China and Taiwan, growing in dry forests and forest edges in mountainous areas.

Ilex chinensis, also known as the long-fruited tree or seven-fruited tree, is distributed in Honshu (west of the Tokai region), Shikoku, and Kyushu in Japan. It is an evergreen tree that grows in dry broad-leaved evergreen forests and Japanese red pine forests along the coast and in low mountains.

All of these trees belong to the genus Ilex in the family Aquifoliaceae. They not only grow in evergreen forests but are also frequently seen planted in parks and gardens, making them extremely familiar and common evergreen trees in Japan. The bright, beautiful red, spherical fruits they bear in winter are also a reason for their popularity.

Morphologically, they share many similarities, such as having thick, glossy leaves characteristic of evergreen trees, and producing red, spherical fruits as mentioned above. They are dioecious (having separate male and female plants).

Additionally, although not a characteristic of the plant itself, the larvae of the fly Asteralobia soyogo can form strange lumps called galls on the buds, which can be a good distinguishing feature from other species (Tokuda et al., 2004). These are called holly galls, soyogo galls, and seven-leaved galls, respectively.

However, distinguishing between these four species is quite difficult, and the lack of distinctive leaf features further complicates the process.

What are the differences between Ilex rotunda, Ilex crenata, Ilex serrata, and Ilex serrata?

Distinguishing between these four species solely by their leaves is quite difficult, but we will introduce them in a way that makes it as easy as possible (Hayashi, 2019).

First, there is a difference in that mature leaves of Ilex rotunda, Ilex crenata, and Ilex serrata do not have serrations, while mature leaves of Ilex crenata have low serrations.

However, be aware that young trees of Ilex rotunda, Ilex crenata, and Ilex serrata may also have serrated edges. It is important to check several leaves.

While it might be possible to identify these four species even as young trees by carefully consulting a plant encyclopedia, I will omit that detail here to avoid making it too complicated.

Regarding the remaining three species, the difference is that the leaf veins of Ilex rotunda and Ilex crenata can be seen with the naked eye, while the leaf veins of Ilex crenata are quite difficult to see with the naked eye.

Furthermore, while the leaf tips of Ilex rotunda and Ilex crenata are pointed, those of Ilex integra, although they do protrude, are rounded.

Regarding Ilex rotunda and Ilex crenata, Ilex rotunda has less wavy leaves, and the color of the midrib when viewed from the underside is green to slightly yellowish, while Ilex crenata has much more pronounced wavy leaves, and the color of the midrib when viewed from the underside is bright yellow. Also, Ilex rotunda grows to be about the same size as Camellia japonica.

I think you can distinguish them to some extent based on the above. Up until now we have only focused on the leaves, but if there are flowers that bloom in early summer (June-July) or fruits that grow in autumn-winter, you can make a more definitive identification.

Regarding the flowers, there is a difference in that the Japanese holly (Ilex crenata) has four petals, while the Japanese holly (Ilex rotunda), Japanese holly (Ilex crenata), and Japanese holly (Ilex serrata) have five petals.

Furthermore, the petals of Ilex rotunda are green and the stamens are slightly reddish, the petals of Ilex crenata are white, and the petals of Ilex serrata are a vibrant purple.

Regarding the fruits, they are all bright red and quite similar, but Ilex crenata can be reliably distinguished. In Ilex rotunda, Ilex crenata, and Ilex serrata, the fruits are clustered together in umbels with short pedicels, forming a mass, but in Ilex crenata, the fruits are solitary and have very long pedicels.

The fruits of the Japanese laurel (Ilex crenata) can sometimes be somewhat oblong. One theory suggests that the name "Japanese laurel" is a corruption of "long fruit tree."

Are there any other similar species?

There are 30 known species of Ilex genus in Japan, and it's impossible to list them all here, but only a limited number of species resemble the four species introduced here.

Similar species to the Japanese holly (Ilex crenata) include Ilex leucoclada and Ilex goshiensis. Ilex leucoclada is a shrub with longer leaves than the Japanese holly, while Ilex goshiensis is a stockier, smaller species. Ilex leucoclada is a species of Japanese holly that has adapted to the snowy climate of the Sea of Japan side of the country, and is considered one of the "Sea of Japan side elements."

Another species that bears fruit in a similar way to Ilex serrata is Ilex sugerokii var. sugerokii, but unlike Ilex serrata, it has serrations on the top half of its leaves.

Japanese holly (Ilex crenata) is a very common species of the genus Ilex, but its leaves are quite small and don't resemble those of other plants.

What are the differences between Japanese holly, golden holly, bean holly, and boxwood? We'll explain how to distinguish between similar species! Why are the flowers so plain to humans but so popular with insects? Do they rely on birds for seed dispersal?

Japanese holly (Ilex crenata) is well-known for being commonly cultivated in gardens as a hedge, but it is originally a species that grows wild in Japan. While distinguishing it from other varieties is not particularly difficult due to its distinctive leaves, there are numerous cultivated varieties, which can make identification a little challenging. Here, we will discuss...

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For information on how to distinguish between Ilex crenata (Japanese holly) and other plants with entire leaves, please see our separate article.

What are the differences between Ternstroemia gymnanthera, Pittosporum tobira, Rhaphiolepis indica, and Ilex crenata? We explain how to distinguish between similar species! Did you know that Ternstroemia gymnanthera is a rare species in the biological world, possessing both male and hermaphroditic flowers on separate plants? And that its fruit deceives birds?

Ternstroemia gymnanthera is an evergreen tree that grows in relatively dry areas near the coast and is quite popular as a garden tree. However, because its leaves are entire and have no serrations, it lacks distinctive features and is often confused with completely different species such as Pittosporum tobira, Rhaphiolepis indica, and Ilex crenata. However, in many cases, the color of the leaf stalks...

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References

Hayashi, Masayuki. 2019. Tree Leaves: Expanded and Revised Edition - Identifying 1300 Species Through Real-Life Scans. Yama-kei Publishers, Tokyo. 824pp. ISBN: 9784635070447

Tokuda, M., Tabuchi, K., Yukawa, J., & Amano, H. 2004. Inter-and intraspecific comparisons between Asteralobia gall midges (Diptera: Cecidomyiidae) causing axillary bud galls on Ilex species (Aquifoliaceae): species identification, host range, and mode of speciation. Annals of the Entomological Society of America 97(5): 957-970. ISSN: 0013-8746. https://doi.org/10.1603/0013-8746(2004)097[0957:IAICBA]2.0.CO;2

Both holly (Ilex crenata) and holly osmanthus belong to the Oleaceae family and are commonly cultivated in urban areas. Young holly trees are also frequently seen in forests. Morphologically, both have serrated leaves, which often leads to confusion between the two species. Furthermore, there are many other plants with "holly" in their name, such as Ilex crenata, Ilex integra, and Nandina domestica, which are also frequently confused. However, careful observation of the leaves, flowers, and fruits reveals clear differences. Interestingly, both holly and Ilex crenata have been found to have both serrated and entire leaves, which is thought to be related to the feeding habits of herbivorous mammals such as Japanese deer. This article will explain the classification and ecology of species that closely resemble holly.

What are holly (Ilex crenata) and holly osmanthus?

Osmanthus heterophyllus, also known as tiger holly, is a small evergreen tree distributed in Honshu (west of the Kanto region), Shikoku, and Kyushu in Japan, growing on the slopes of slightly dry hills. It is also commonly planted in gardens as an ornamental plant, and escaped cultivation is common.

Osmanthus x fortunei, also known as holly osmanthus, is a presumed hybrid of holly and Osmanthus asiaticus. It is cultivated in parks, streets, and gardens, and sometimes escapes cultivation.

Both belong to the genus Osmanthus in the family Oleaceae, and can be seen being cultivated even in urban areas. As for holly, young trees can often be seen in forests.

Morphologically, they share common characteristics such as serrated leaves, a corolla with a tube and four lobes, and a drupe fruit (Kanagawa Prefecture Flora Survey Association, 2018).

Therefore, these two species are often confused. Moreover, there are many other plants with "holly" in their name, such as Ilex crenata, Ilex integra, and Nandina domestica, and these are also frequently confused.

What is the difference between holly and holly osmanthus?

Holly and holly olive can be distinguished by the shape of their leaves (Hayashi, 2019).

Specifically, in the leaves with serrations, holly has 3 to 5 pairs of larger serrations, while holly osmanthus has 6 to 10 pairs of finer serrations.

This can be understood by considering that Osmanthus heterophyllus is a hybrid of Osmanthus fragrans, which has coarsely serrated leaves, and Osmanthus fragrans, which has finely serrated leaves.

Also, although it's not often pointed out, there seem to be differences in the shape of the flowers as well.

In holly, the corolla lobes are curved backward and the stamens clearly protrude from the corolla, whereas in holly osmanthus, the corolla lobes are flat and the stamens are usually contained within the corolla.

This, too, can be considered a result of the holly osmanthus inheriting elements of the silver osmanthus flower.

What are the differences between Japanese holly (Ilex crenata), Japanese holly (Ilex rotunda), and European holly (Ilex serrata)?

Other species with names similar to holly include Japanese holly (Ilex crenata) and European holly (Ilex rotunda).

Ilex cornuta, also known as Japanese holly (Ilex cornuta), has the standard Japanese name Yabane-hiiragimochi (arrow feather holly), and is also called Hiiragimodoki (false holly) or Shina-hiiragi (Chinese holly). Native to China and the Korean Peninsula, it is an evergreen shrub sometimes cultivated as an ornamental plant in gardens, hedges, or pots.

European holly (Ilex aquifolium), also known as Christmas holly, is an evergreen shrub native to Europe and West Asia, cultivated for ornamental purposes. It is used in Christmas decorations.

These species are named after the fact that their leaves have sharp serrations, similar to holly, and they are also evergreen trees, which likely contributes to the confusion.

However, their classifications are quite different to begin with. As mentioned above, Japanese holly belongs to the Oleaceae family, while Japanese holly and European holly belong to the Aquifoliaceae family.

It's common for flowers and fruits to differ significantly between different plant families.

Regarding the flowers, Japanese holly (Ilex crenata) is dioecious, meaning that each flower has either stamens or pistils, whereas Japanese holly (Ilex crenata) and European holly (Ilex rotunda) are monoecious, meaning that each flower has both stamens and pistils. Additionally, Japanese holly blooms from November to December, while Japanese holly and European holly bloom from April to May.

Regarding the fruit, there is a difference: Japanese holly ripens to a purplish-black color from May to July, while Japanese holly and European holly ripen to red in November to December.

If you see bright red, ripe berries in winter, it's definitely not a holly tree.

There are also differences in the leaves. Holly and holly osmanthus have petioles that are 4 to 15 mm long, while Japanese holly and European holly have petioles that are only 2 to 5 mm long.

The rectangular shape of the leaves of Ilex crenata, with thorns at all four corners, is unique to both Ilex crenata and Ilex integra, and this is an important distinguishing feature.

What is the difference between holly and mahonia?

Berberis japonica, also known as holly maize, is another species that is often confused with holly.

However, Mahonia japonica belongs to the Berberidaceae family, which is a completely different group from holly, which belongs to the Oleaceae family.

[Seed Plant Encyclopedia #123] What are the species of the Berberidaceae family? Photo list

Berberidaceae are perennial herbs or shrubs. Their leaves are alternate and can be simple or compound. The sepals are arranged in groups of three in 3-4 whorls, or two in 4 whorls; the outer 1-2 whorls are smaller and fall off quickly during flowering, while the inner 2 whorls are larger and petal-like. The petals are 2 or...

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Mahonia japonica has odd-pinnately compound leaves, meaning each leaf is divided into 5 to 9 pairs of "leaflets," which is different from the simple-leaved holly.

The flowers of Mahonia are yellow, but those of Holly are white.

If you observe carefully, you should be able to easily distinguish them.

It should be noted that the genus Mahonia also includes other species such as Narrow-leaved Mahonia and Flat-leaved Mahonia, so distinguishing between them is a separate matter.

What are the differences between Mahonia japonica, Narrow-leaved Mahonia japonica, and Flat-leaved Mahonia japonica? We'll explain how to distinguish between similar species!

Mahonia japonica, Narrow-leaved Mahonia japonica, and Flat-leaved Mahonia japonica all belong to the Berberidaceae family, genus Berberis. They have odd-pinnately compound leaves with coarse, needle-like serrations and are frequently cultivated as ornamental plants due to their ease of growth. However, few people may be able to properly distinguish between the three species...

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Why do holly plants have leaves with thorns and leaves without?

It is known that holly has both thorny leaves (serrated leaves) and leaves without thorns (entire leaves).

Young holly trees have many serrated leaves, while as they age, they tend to have more entire leaves.

Why does the holly tree have two types of leaves, and why do entire leaves become more common as it ages?

Although there are no actual experiments to support this, it is assumed that young trees are short and at high risk of being eaten by herbivorous mammals such as Japanese deer, but as they get older and grow taller, the risk of being eaten decreases (Sonike, 2016).

In such cases, it is important for young plants to develop serrated leaves to prevent them from being eaten. However, it is likely that producing sharp, hard thorns is costly and energy-consuming, so as the plant ages, it probably develops more entire leaves to reduce waste.

What are the seed dispersal methods?

The exact method of holly seed dispersal is not fully understood, but it is known to be bird-dispersed, and at least bulbuls are known to eat them (Ueda, 1999).

You can often see young holly trees scattered throughout the forest, and it's clear that these have sprouted from bird droppings.

References

Hayashi, Masayuki. 2019. Tree Leaves: Expanded and Revised Edition - Identifying 1300 Species Through Real-Life Scans. Yama-kei Publishers, Tokyo. 824pp. ISBN: 9784635070447

Kanagawa Prefecture Flora Survey Association. 2018. Kanagawa Prefecture Flora 2018 (Electronic Edition). Kanagawa Prefecture Flora Survey Association, Odawara. 1803pp. ISBN: 9784991053726

Sonoike, Kimiyoshi. 2016. Plant shapes have meaning. Bere Publishing, Tokyo. 293pp. ISBN: 9784860644703

Ueda, Keisuke. 1999. Seed Dispersal: The Evolution of Mutual Aid, Vol. 1: Seeds Carried by Birds. Tsukiji Shokan, Tokyo. ISBN: 9784806711926

Rhamnus japonica is a deciduous shrub that grows relatively rarely in Japan, but it is often compared to other similar species such as Rosa chinensis and Rhamnus japonica. Rhamnus japonica shares a similar name, and morphologically, both species have drupe fruits and flowers and fruits that grow in clusters in the leaf axils, which may lead to confusion for those unfamiliar with them. Furthermore, both Rhamnus chinensis and Rhamnus japonica belong to the Rhamnus genus of the Rhamnaceae family and are taxonomically similar, sharing many common features. However, there is a taxonomic gap between them, and Rhamnus chinensis can be distinguished by carefully observing its leaves. This article will explain the classification and morphology of Rhamnus japonica, Rosa chinensis, and Rhamnus japonica.

What are Rhamnus japonica, Ilex serrata, and Ilex serrata?

Rhamnus japonica var. decipiens, also known as black buckthorn, is a deciduous shrub distributed in the cool temperate zones of Hokkaido, Honshu, Shikoku, and Kyushu in Japan, and is somewhat rarely found growing in forests and rocky areas from mountainous to hilly regions (Kanagawa Prefecture Flora Survey Association, 2018).

Rhamnus davurica var. nipponica, also known as black rose, is a deciduous shrub distributed in Honshu, Japan (central and northern regions), and rarely grows on slopes and near water in lowlands and mountainous areas.

Ilex serrata, also known as Japanese holly, is a deciduous shrub distributed in Honshu, Shikoku, and Kyushu in Japan, as well as in China, growing in wetlands or damp deciduous broad-leaved forests (Mogi et al., 2000).

The names of the black buckthorn and the Japanese buckthorn are similar, and people who have never seen them may confuse them. One theory is that the Japanese name "kuro-umemodoki" (black buckthorn) comes from the fact that its fruit and branching pattern resemble those of the Japanese buckthorn, and that its fruit is black. Both are deciduous shrubs, dioecious, have drupe fruits, and their flowers and fruits grow in clusters in the leaf axils (or appear to grow in clusters).

Both Rhamnus japonica and Rhamnus japonica belong to the Rhamnus genus of the Rhamnus family, and their leaves, flowers, and fruits are very similar. The ovary has 2 to 4 chambers, and the fruit is spherical with 2 to 4 seeds.

Furthermore, these two species within the genus Rhamna are very similar, sharing the characteristic of having only 3 to 5 pairs of lateral veins on their leaves, and sometimes having thorns at the tips of their branches. Therefore, they are easily confused.

What is the difference between black buckthorn and Japanese buckthorn?

However, first of all, Rhamnus japonica and Ilex serrata belong to completely different groups.

There is a significant difference between Rhamnus japonica and Ilex crenata: Rhamnus japonica belongs to the genus Rhamnus in the family Rhamnaceae, while Ilex serrata belongs to the genus Ilex in the family Aquifoliaceae. Therefore, it is likely that there are also significant differences in their morphology.

There are too many specific differences to list, but if we only consider the leaves, in Rhamnus japonica, the leaf blade is small, the underside of the leaf is glossy, and the lateral veins of the leaf are curved so much that they run parallel to the main vein. In contrast, in Ilex serrata, the leaf blade is large, the underside of the leaf is not glossy, and the lateral veins of the leaf grow almost perpendicular to the main vein and curve as they extend.

The flowers are completely different. In black buckthorn, the flowers are yellowish-green with four petals that extend to the tip in a tail-like manner, while in Japanese holly, the flowers are pale purple with four to five petals that have rounded tips.

Perhaps the name was derived from the image of the plant bearing fruit in the past, but upon closer observation, you'll realize they belong to completely different groups.

Of course, the fruit of the black buckthorn is usually black when ripe, but the fruit of the Japanese holly is red when ripe.

What is the difference between Rhamnus japonica and Rhamnus japonica?

Rhamnus japonica and Rhamnus japonica are very similar in appearance because they belong to the exact same classification.

However, they can be distinguished by the shape of their leaves (Kanagawa Prefecture Flora Survey Association, 2018; Hayashi, 2019).

Specifically, the difference lies in the fact that Rhamnus japonica has small, obovate leaves with a wedge-shaped base and well-developed short branches, while Rosa chinensis has large, oval to oblong leaves.

While some Rhamnus japonica species have larger leaves, the key difference with Rhamnus japonica is the presence of long, oval-shaped leaves.

What are the varieties and cultivars of Rhamnus japonica (black buckthorn)?

Many varieties have been identified for both Rhamnus japonica and Rhamnus japonica.

Rhamnus japonica (in the narrow sense) var. decipiens is a variety with leaves 3-6 cm long.

Ezo-no-kuromedoki var. japonica is distributed in Hokkaido and the Sea of Japan side of Honshu, and is a large variety with leaves 5-12 cm long.

Rhamnus japonica var. microphylla is distributed in western Japan and grows in limestone and serpentine areas. It is a small variety with leaves 1-3 cm long.

Rhamnus japonica var. decipiens f. senanensis is a variety characterized by fine hairs covering the entire underside of its leaves.

Blue-green buckthorn var. decipiens f. chlorocarpa is a variety with blue-green fruits (Honda, 1933).

Rosa davurica var. davurica is distributed in Korea, northern China, and Dahurya.

Rose of the Black-tailed Rose var. nipponica f. pubescens is a variety that has hairs all over its underside.

What is the structure of a flower?

Rhamnus japonica blooms from April to May. It is dioecious (having separate male and female plants). The flowers grow in clusters in the leaf axils, are yellowish-green, and have tetramerous flowers.

Black roses bloom from May to June. They are dioecious (having separate male and female plants). The flowers are clustered in the leaf axils and short branches near the base of young branches, and are tetramerous, yellowish-green, and 4-5 mm in diameter. Male flowers are numerous, while female flowers are few. The pedicels are 7-10 mm long. The calyx lobes are narrowly triangular with pointed tips, and the calyx tube is bell-shaped. The style of the female flower is long and protruding, bifurcated at the tip, and the branches curve downwards.

Ilex serrata flowers in June. It is dioecious (having separate male and female plants). Pale purple flowers bloom in the leaf axils of the current year's branches. The inflorescence axis is extremely short, so the flowers appear to be clustered together. Male inflorescences have 5 to 20 flowers, while female inflorescences have 2 to 4 flowers. The flowers are 3 to 4 mm in diameter. The petals are 4 to 5 in number, oval-shaped, and about 4 mm long. There are 4 to 5 sepals. Male flowers have 4 to 5 stamens and a vestigial pistil. Female flowers have vestigial stamens. The ovary is spherical and the style is very short.

What is the structure of the fruit?

The fruits of the Rhamnaceae genus are all drupe. A drupe is a fruit in which the endocarp surrounding the seed hardens to form a pit, and the mesocarp surrounding the pit is usually fleshy.

The fruit of the buckthorn is a drupe. It ripens to black and contains two seeds.

The fruit of the black rose is a drupe. It is obovate-spherical, 6-8 mm in diameter, and ripens to black.

The fruit of the Japanese holly (Ilex serrata) is a drupe. It is spherical, about 5 mm in diameter, ripens to red in September and October, and remains on the tree even after the leaves have fallen. Inside are 4 to 5 seeds. The seeds are triangular-elliptical in shape, about 2 mm long, and have a smooth surface.

References

Hayashi, Masayuki. 2019. Tree Leaves: Expanded and Revised Edition - Identifying 1300 Species Through Real-Life Scans. Yama-kei Publishers, Tokyo. 824pp. ISBN: 9784635070447

Honda, M. 1933. Nuntia ad Floram Japoniae XX. The Botanical Magazine 47(556): 296-299. https://doi.org/10.15281/jplantres1887.47.296

Kanagawa Prefecture Flora Survey Association. 2018. Kanagawa Prefecture Flora 2018 (Electronic Edition). Kanagawa Prefecture Flora Survey Association, Odawara. 1803pp. ISBN: 9784991053726

Mogi, T., Ota, K., Katsuyama, T., Takahashi, H., Shirokawa, S., Yoshiyama, K., Ishii, E., Sakio, H., and Nakagawa, S. 2000. Flowers Blooming on Trees: Polypetalous Flowers (Vol. 2, 2nd edition). Yama-kei Publishers, Tokyo. 719pp. ISBN: 9784635070041

Japanese holly (Ilex crenata) is well-known for being commonly cultivated in gardens as hedges, but it is originally a species that grows wild in Japan. Distinguishing it from other species is not difficult, as its leaves are distinctive, although the distinction is not particularly clear. However, there are many cultivated varieties, and distinguishing them can be a little difficult. This article will show how to distinguish between several cultivated varieties, focusing on Japanese holly (Ilex crenata) and Japanese holly (Ilex crenata var. japonica). They can mainly be distinguished by the way the leaves are arranged and shaped. It should be noted that it is a completely different plant from boxwood (Ilex crenata). Its flowers seem to be quite popular, with a large number of insects visiting them, both in terms of species and individual numbers. However, the reason for this is unknown due to insufficient research. Seed dispersal relies on birds, and it seems to be a popular food source for birds as well, but there is insufficient research on which birds prefer it and what nutrients it contains. This article will explain the classification, pollination ecology, and seed dispersal of Japanese holly.

What are the differences between Ilex crenata, Buxus microphylla, Buxus microphylla, and Buxus sieboldiana?

Ilex crenata var. crenata, also known as Japanese holly (Ilex crenata var. crenata), is an evergreen small tree distributed in Honshu (south of Iwate Prefecture), Shikoku, and Kyushu, and is widely found in secondary forests on hills and mountainous areas (Hayashi, 2014; Kanagawa Prefecture Flora Survey Association, 2018). It is also cultivated in gardens and cemeteries, and there are many varieties. It is dioecious, meaning it has separate male and female plants.

Although there are many species in the genus Ilex of the family Aquifoliaceae, which includes Japanese holly (Ilex crenata), there are no species that are difficult to distinguish from each other, except for the large-leaved holly (Ilex crenata var. crenata f. latifolia), which is common in warm coastal areas, and the rare Japanese holly (Ilex rugosa), which is common in forests, due to their small leaves.

However, since there are several horticultural varieties, it can be difficult to distinguish between them. In particular, we will explain how to distinguish between Kinnmetsuge (Golden-budded Boxwood) and Mametsuge (Bean Boxwood) f. bullata, which are frequently searched for.

The main difference between Japanese holly and Japanese boxwood is that while the young leaves of Japanese holly are indistinguishable from mature leaves, the young leaves of Japanese boxwood are yellow. This is the most significant difference. However, once the young leaves are gone, it becomes difficult to distinguish between the two.

There are other differences between Japanese holly (Ilex crenata) and golden boxwood (Buxus microphyllus). Japanese holly has relatively few leaves and is sparse, while golden boxwood has relatively many leaves and appears dense from the outside. Also, Japanese holly has large, nearly oblong leaves, while golden boxwood has small, nearly circular leaves. This is probably because they were selected to have dense foliage for use as screens in horticulture.

There also seems to be a variety called Golden Gem, but while the leaves of the common boxwood (Buxus microphylla) return to their original color as it grows, the Golden Gem variety turns yellow-green when it matures.

On the other hand, the difference with Japanese holly is that while Japanese holly has flat leaves with only slight bends along the main vein, Japanese holly has leaves that curve upwards. This should be easy to spot.

In addition to these, there are many other varieties, including Ilex crenata f. microphylla, Ilex crenata f. longifolia with linear-elliptical leaves, Ilex nummularia f. nummularia with tortoise-shell shaped leaves, and Ilex crenata f. watanabeana with yellow fruits.

The aforementioned Ilex crenata var. latifolia can be distinguished from Ilex crenata by its larger leaves, rounded leaf tips, serrated edges, and reddish-yellowish-green mature leaves. This characteristic is limited to the wild species.

The Japanese holly (Ilex crenata) is named after the boxwood (Tsuga japonica), which belongs to the Buxaceae family and is a completely different classification. In Japanese holly, the leaves are alternate and have serrated edges, while in Japanese boxwood (Tsuga japonica), the leaves are opposite, entire, and have notched or rounded tips.

[Seed Plant Encyclopedia #130] What are the species of the Buxaceae family? Photo list

The Buxaceae family consists of shrubs or trees. The flowers are unisexual and monoecious. There are no petals, and the calyx has 4 to 12 lobes. There are 4 stamens opposite the calyx. The ovary has 3 superior chambers, rarely 2 or 4. The fruit is a capsule or drupe. There are approximately 100 species in 5 genera worldwide, with 2 genera and 3 species distributed in Japan. This article...

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There are few research examples, but it seems to be very popular with various insects?

The flowering period is from June to July. Male plants produce male flowers consisting only of stamens, while female plants produce female flowers consisting only of pistils. The flowers are white, composed of four petals, and, as far as humans can see, they don't seem to have many distinctive features.

It's very inconspicuous and easily overlooked, but perhaps because it produces countless flowers, it seems to be quite popular with insects. Studies have recorded visits from Japanese honeybees, European honeybees, and the pale blue butterfly (Fujiwara & Yamaguchi, 2020; Nanba, 2020), but I've actually seen on the internet that it's visited by small ants, hoverflies, a species of blowfly, a small green flower beetle, and a species of click beetle. According to these reports, not only are many species attracted, but the number of individuals visiting is also large. A small species of thrips can be seen in this photograph. However, the reason for its popularity is unclear due to insufficient research. I hope for further research in the future.

Ilex crenata is black, spherical in shape, and its seeds are dispersed by birds.

The fruit is black and spherical, and the seeds are dispersed by birds (Karasawa, 1978; Fujiwara and Yamaguchi, 2020).

A study conducted in urbanized areas of eastern Tokyo and western Chiba Prefecture investigated seeds contained in the droppings of fruit-eating birds (Karasawa, 1978). The results showed that among the eight species with an occurrence rate of 50% or higher and 50 or more specimens collected, Japanese holly (Ilex crenata) was included. Since this study included planted individuals in urban areas, it is unclear whether the results are similar in forests, but since young Japanese holly trees are certainly seen all over the forest, it seems certain that it is a favorite of birds.

However, this study did not clarify which specific birds prefer the fruit. Other observations have shown that pigeons, bulbuls, and thrushes eat it (Kanouchi, 2021), so it is possible that these birds are the main ones that eat the fruit and disperse the seeds.

However, it is unclear how the black, spherical shape of the fruit, unlike red fruit, affects birds' preferences. This is something we hope will be explored in future research.

Are there any other similar species?

Tsuruga is very similar to Ilex crenata, but it rarely grows in forests, its trunk creeps along the ground, and its leaves have a net-like pattern of wrinkles.

While there are many other species in the Ilex genus besides Ilex crenata, as mentioned above, their leaves are large and not very similar. Please check out the other article for more information.

What are the differences between Ilex rotunda, Ilex crenata, Ilex serrata, and Ilex serrata? An explanation of how to distinguish between similar species.

Ilex rotunda, Ilex crenata, Ilex serrata, and Ilex serrata all belong to the Ilex genus of the family Aquifoliaceae. They not only grow in evergreen broad-leaved forests but are also frequently seen planted in parks and gardens, making them extremely familiar and common evergreen trees in Japan. They share thick leaves and beautiful red fruits...

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References

Fujiwara, Ayumi & Yamaguchi, Kikuji. 2020. Seasonal changes in flowering plants at Miyagi Gakuin Women's University: A survey of honeybee nectar and pollen source plants on the university campus. Research Report of the Institute for Living Environment Sciences 52: 19-24. ISSN: 1346-6534, https://doi.org/10.20641/00000488

Hayashi, Masayuki. 2014. 1100 Tree Leaves Identified Through Real-Life Scans. Yama-kei Publishers, Tokyo. 759pp. ISBN: 9784635070324

Kanagawa Prefecture Flora Survey Association. 2018. Kanagawa Prefecture Flora 2018 (Electronic Edition). Kanagawa Prefecture Flora Survey Association, Odawara. 1803pp. ISBN: 9784991053726

Kanouchi, Takuya. 2021. Handbook of Wild Birds and Tree Nuts (Revised and Expanded Edition). Bun-ichi Sogo Shuppan, Tokyo. 104pp. ISBN: 9784829981672

Karasawa, Koichi. 1978. A study on the diet and seed dispersal of fruit-eating birds in urban areas. Birds 27(1): 1-20. https://doi.org/10.3838/jjo1915.27.1

Source

This article is a significantly expanded version of a piece originally published in the following book.

Ternstroemia gymnanthera is an evergreen tree that grows in relatively dry areas near the coast and is quite popular as a garden tree. However, because its leaves are entire and have no serrations, it lacks distinctive features and is often confused with completely different species such as Pittosporum tobira, Rhaphiolepis indica, and Ilex crenata. However, in most cases, it can be distinguished by observing the color of the petiole and the condition of the veins on the upper and lower surfaces of the leaf. If there are flowers or fruits, it can be distinguished even more reliably. Ternstroemia gymnanthera has a sex system that is quite rare among plants, with individuals that produce only hermaphroditic flowers (hermaphroditic plants) and individuals that produce only male flowers (male plants). This is called "male-flowered, hermaphroditic-flowered, dioecious." This is thought to have evolved to counteract the disadvantages caused by inbreeding called "inbreeding depression," but it is a sex system that is still shrouded in mystery. The fruit is also mysterious; it is known to be eaten by birds and its seeds dispersed, but when ripe it only turns red and does not contain water like a berry. Moreover, when ripe, the pericarp dries out further and loses its shape, exposing the seeds. And now the seeds are red, attracting attention. The fact that they turn red despite being dry and lacking nutrients suggests that they are mimicking nutritious fruit to deceive birds. However, the reason why the fruit changes shape after turning red, and why the seeds also turn red, is still not well understood. Perhaps a different type of bird visits. This article will explain the classification, pollination ecology, and seed dispersal of Ternstroemia gymnanthera.

What are the differences between Ternstroemia gymnanthera, Eurya japonica, and Cleyera japonica?

Ternstroemia gymnanthera, also known as Mokkoku, is an evergreen tree that grows in relatively dry areas near the coast, distributed throughout Japan (including the southwestern islands of Honshu, west of the Kanto region), Shikoku, Kyushu, the Ryukyu Islands, the southern Korean Peninsula, Taiwan, China, and extending from Southeast Asia to India (Kitamura & Murata, 1979; Mogi et al., 2000). In Japan, it has been commonly used as a garden tree due to its resistance to diseases and pests, its beautiful leaves, and its well-formed shape. It belongs to the family Cleyera.

The family Cleyraceae also includes the genera Eurya and Cleyera (Kanagawa Prefecture Flora Survey Association, 2018). However, while Eurya has serrated leaves and Cleyera does not have leaves clustered at the branch ends, Ternstroemia gymnanthera has serrated leaves and its leaves are clustered at the branch ends, which are clear differences, so it may be less likely to get confused.

What are the differences between Eurya japonica, Eurya japonica, and Sakaki? We'll explain how to distinguish between similar species! Do they bloom in early spring because they rely on bees and flies for pollination?

Hisakaki, Hamahisakaki, and Sakaki all belong to the family Cleyera (or Theaceae). Hisakaki and Sakaki, in particular, have been considered "yorishiro" (objects that house divine spirits) in Shintoism since ancient times and have been traditionally cultivated in Japan. However, their similar names may often lead to confusion...

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What are the differences between Ternstroemia gymnanthera, Pittosporum tobira, Rhaphiolepis indica, and Ilex crenata?

What might be more confusing are the species that belong to a completely different group but have entire leaves and are used as garden trees. Typical examples include Pittosporum tobira, Rhaphiolepis indica, and Ilex crenata.

Pittosporum tobira, also known as sea laurel or door tree, is distributed in Honshu, Shikoku, Kyushu, and the Ryukyu Islands of Japan, as well as in southern Korea. It is an evergreen shrub or small tree that grows naturally in coastal forests and forest edges, and also escapes cultivation into inland broad-leaved evergreen forests. In Japan, it is planted in coastal sand dune forests and gardens. It belongs to the Pittosporaceae family.

Rhaphiolepis indica var. umbellata, also known as Indian hawthorn, is an evergreen shrub distributed in Honshu, Shikoku, Kyushu, the Ryukyu Islands, and the Ogasawara Islands of Japan; as well as in Korea, China, Taiwan, and Southeast Asia, growing near the coast. It is commonly planted in parks and other public spaces. It belongs to the rose family. While there are various varieties of Indian hawthorn, the one most often confused is Rhaphiolepis indica f. ovata, which has leaves without serrations.

Ilex integra, also known as Japanese holly (Ilex integra), is an evergreen tree distributed in Honshu (south of the Tohoku region), Shikoku, Kyushu, and the Ryukyu Islands of Japan, growing in evergreen broad-leaved forests. It belongs to the family Aquifoliaceae.

How can we distinguish between these and other species of Japanese holly?

The best way to distinguish them based solely on their leaves is that the petioles of Ternstroemia gymnanthera are usually bright red (Hayashi, 2014). Pittosporum tobira has green petioles, and Ilex crenata has green or inconspicuous purple petioles. Rhaphiolepis indica can turn red, but this is not uniform and varies depending on the position of the leaf, and it is often green.

Furthermore, in Ternstroemia gymnanthera, the veins on the underside of the leaves are barely visible. However, with the exception of Ilex crenata, Pittosporum tobira and Rhaphiolepis indica have clearly visible veins on the underside of their leaves.

If we consider them individually, in Pittosporum tobira, the leaf margins usually curl towards the underside of the leaf, and the veins on the underside of the leaf are clearly visible, whereas this is not the case with Ternstroemia gymnanthera.

In Rhaphiolepis indica, there are differences between individual leaves; some have serrations, and the veins on the underside of the leaves are clearly defined, whereas this is not the case with Ternstroemia gymnanthera.

In holly (Ilex crenata), the veins are not very prominent on the upper surface of the leaves, and the tips of the leaves protrude slightly, but this is not the case with Ternstroemia gymnanthera (Turkish holly).

By considering all of the above factors, you should be able to distinguish between them.

I will omit the detailed morphology of the flowers and fruits, but as you can see in the photos, they are completely different because they belong to different families. The mature fruits of Ternstroemia gymnanthera and Pittosporum tobira expose the seeds, but in Ternstroemia gymnanthera, the fruit splits irregularly to expose the seeds, while in Pittosporum tobira, it splits regularly into three lobes to expose the seeds. If you check the fruit, you can definitely distinguish between them.

Are there any other similar species?

The distinctions between species in the genus Ilex, which are closely related to Ilex crenata, are explained in a separate article.

What are the differences between Ilex rotunda, Ilex crenata, Ilex serrata, and Ilex serrata? An explanation of how to distinguish between similar species.

Ilex rotunda, Ilex crenata, Ilex serrata, and Ilex serrata all belong to the Ilex genus of the family Aquifoliaceae. They not only grow in evergreen broad-leaved forests but are also frequently seen planted in parks and gardens, making them extremely familiar and common evergreen trees in Japan. They share thick leaves and beautiful red fruits...

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Please see our separate article for information on the differences between species of Rhaphiolepis indica (including Ternstroemia gymnanthera). Although Ternstroemia gymnanthera has a somewhat confusing name, it is a relative of Rhaphiolepis indica and is unrelated to Ternstroemia gymnanthera.

What are the differences between Rhaphiolepis indica, Rhaphiolepis umbellata, and Ternstroemia gymnanthera? An explanation of how to distinguish between similar species.

Rhaphiolepis indica, Rhaphiolepis umbellata, and Rhaphiolepis ternata all belong to the genus Rhaphiolepis in the family Rosaceae. While they naturally grow on coastlines, they are frequently seen planted in urban areas. However, the classification of the genus Rhaphiolepis is complex even at the species level, and there are many other species besides the three mentioned above...

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What is the structure of a Ternstroemia gymnanthera flower?

The flowering period of Ternstroemia gymnanthera is from June to July, blooming from early summer to summer (Mogi et al., 2000). Flowers about 1.5 cm in diameter hang downwards in the leaf axils. The flowers are white, later turning yellowish. The narrow, oblong petals, 8-10 mm long, open flat, and there are numerous stamens. There are male and hermaphroditic flowers. In male flowers, the stamens are arranged in three rows and have a lot of pollen, and the pistil is small and reduced. In hermaphroditic flowers, the stamens are arranged in one row and have less pollen, and one pistil can be seen.

Why did the unusual sex system "male flowers, hermaphrodite flowers, dioecious plants" come about?

As mentioned above, the gender of the Japanese holly has some distinctive characteristics.

This means that there are individuals that produce only hermaphroditic flowers ( hermaphroditic plants) and individuals that produce only male flowers (male plants). In other words, it's a world where both hermaphrodites and only males exist.

This is called androdioecy, or dioecy of male and hermaphroditic flowers on separate plants. The opposite case, where some plants produce only hermaphroditic flowers and others only female flowers, is difficult for humans to understand, but it is relatively well known in the plant world (Maki & Yahara, 1993). Dioecy of male and hermaphroditic flowers is an extremely rare case in plants, and only a handful of organisms exist in the world (Charlesworth, 1984)!

Why do they employ such a sexual system?

This is a very difficult topic. One theory suggests that originally, plants only existed as individuals that produced only hermaphroditic flowers, but for some reason, if individuals with similar genes come together, inbreeding can occur, resulting in the production of very weak offspring (this is well known in human history and is called inbreeding depression).

In such a situation, if a plant were to produce only male flowers and focus solely on pollen production, the same thing would happen if the pollen were carried by insects to the flowers of nearby plants. However, if it were lucky enough to be carried far away, it might be able to produce healthy offspring. This is thought to be the reason why male plants are born. However, even if this is the case, the detailed conditions are still not fully understood. It would be interesting if this complex mystery were to be researched and solved someday.

Do male flowers, which are full of pollen, attract bees?

For the reasons mentioned above, it can be observed that male flowers, in particular, have a large amount of pollen, suggesting that the flowers of the Japanese holly (Turkish japonica) attract bees that carry a lot of pollen.

However, my research did not yield any papers that specifically listed the visiting insects. I did find four photos on the internet of European honeybees (Apis mellifera) visiting flowers in Japan, so I suspect that many of the bees are indeed there for pollination.

Even though the flower shapes differ significantly between *Tetramorium laevigata* and *Tetramorium dentata*, which are related species to *Tetramorium*, it has been confirmed that bees visit them and carry pollen using a special method called "vibration pollination" (Bittrich et al., 1993). This further supports the prediction that bees will visit the flowers.

The fruit of the Japanese holly (Mokkoku) is a capsule, yet it's dispersed by birds!?

The fruit of Ternstroemia gymnanthera is a capsule. It is spherical, 1-1.5 cm in diameter, and ripens red in October and November. The pericarp is fleshy and splits open irregularly when ripe, releasing orange-red seeds. The seeds are obovate, about 7 mm long.

How is seed dispersal carried out?

Several Japanese studies have shown that the fruits of the Japanese holly (Turkish japonica) are eaten by birds such as the Oriental Turtle Dove (Streptopelia orientalis), the Daurian Redstart (Phoenicurus auroreus), the Varied Tit (Sittiparus varius), and the Carrion Crow (Corvus corone) (Fujita and Shinohara, 2001), as well as mammals such as the Yakushima Macaque (Macaca fuscata yakui) (Otani, 2005). However, considering its size and habitat, it is thought that it is more often eaten by birds than mammals. In addition, there have been observations of thrushes, flycatchers, and the Japanese White-eye (Zosterops japonicus) eating the fruits (Kanouchi, 2021), and a study in Korea has also recorded that it is eaten by the Brown-eared Bulbul (Hypsipetes amaurotis) (Kim et al., 2015).

By the way, the fruit of the Japanese holly is a little strange. It turns red when ripe, which is clearly to attract animals and get them to eat it, but it doesn't contain much water like a berry. Moreover, when it ripens, the pericarp dries out and loses its shape, exposing the seeds. And then the seeds turn red to attract animals.

It's still unclear how this is perceived by birds that eat the fruit of the Japanese holly tree. However, considering this progression, there may be two phases: one that appeals to birds that eat the whole fruit, and another that appeals to birds that eat only the seeds.

In the phase where the fruit is intended to appeal to birds that eat it whole, the thin peel makes it unsuitable as a food source for birds. In other words, it seems that the Japanese holly (Mokkoku) deceives birds by mimicking ordinary fruits by turning red (Ueda, 1999).

It's unclear to what extent the phase of appealing to birds that only eat seeds contributes to seed dispersal. In the case of seeds, unless the seed coat is made quite strong, there is a risk that it will simply be digested by birds and used for nutrition.

As you can see, there are many mysteries surrounding both the flowers and fruits of this plant. When you come across a Japanese holly tree, try observing it carefully to see what animals it interacts with; you might discover something new.

References

Bittrich, V., Amaral, MC, & Melo, GAR 1993. Pollination biology of Ternstroemia laevigata and T. dentata (Theaceae). Plant Systematics and Evolution 185(1): 1-6. ISSN: 0378-2697, https://doi.org/10.1007/BF00937716

Charlesworth, D. 1984. Androdioecy and the evolution of dioecy. Biological Journal of the Linnean Society 22(4): 333-348. ISSN: 0024-4066, https://doi.org/10.1111/j.1095-8312.1984.tb01683.x

Fujita, Kaoru & Shinohara, Yukiko. 2001. Dispersal of planted trees into natural forests by birds and mammals. Strix 19: 103-113. https://mobile.wbsj.org/nature/public/strix/19/Strix19_12.pdf

Hayashi, Masayuki. 2014. 1100 Tree Leaves Identified Through Real-Life Scans. Yama-kei Publishers, Tokyo. 759pp. ISBN: 9784635070324

Kanagawa Prefecture Flora Survey Association. 2018. Kanagawa Prefecture Flora 2018 (Electronic Edition). Kanagawa Prefecture Flora Survey Association, Odawara. 1803pp. ISBN: 9784991053726

Kanouchi, Takuya. 2021. Handbook of Wild Birds and Tree Nuts (Revised and Expanded Edition). Bun-ichi Sogo Shuppan, Tokyo. 104pp. ISBN: 9784829981672

Kim, EM, Kang, CW, Won, HK, Song, KM, & Oh, MR 2015. The status of fruits consumed by brown-eared bulbul (Hypsypetes amaurotis) as a seed dispersal agent on Jeju Island. Journal of the Korean Society of Environmental Restoration Technology 18(1): 53-69. https://doi.org/10.13087/kosert.2015.18.1.53

Kitamura, Shiro & Murata, Gen. 1979. Illustrated Flora of Japan in Color: Woody Plants, Vol. 2. Hoikusha, Osaka. 630pp. ISBN: 9784586300501

Maki, Masayuki & Yahara, Tetsuichi. 1993. Evolution of asymmetric sexual expression in plants. Chemistry and Biology 31(4): 242-245. ISSN: 0453-073X, https://doi.org/10.1271/kagakutoseibutsu1962.31.242

Mogi, Toru; Ota, Kazuo; Katsuyama, Teruo; Takahashi, Hideo; Shirokawa, Shiro; Yoshiyama, Hiroshi; Ishii, Hidemi; Sakio, Hitoshi; and Nakagawa, Shigetoshi. 2000. Flowers Blooming on Trees: Polypetalous Flowers (Vol. 2, 2nd edition). Yama-kei Publishers, Tokyo. 719pp. ISBN: 9784635070041

Otani, T. 2005. Characteristics of medium-sized mammals as seed dispersers of berries—mainly using Japanese macaques as an example—. Nagoya University Journal of Forest Science 24: 7-43. https://doi.org/10.18999/nagufs.24.7

Ueda, Keisuke. 1999. Unexpected Birds' Unexpected Preferences: Who Eats the Inconspicuous "Dry Fruit"?. In: Ueda, Keisuke (Ed.), Seed Dispersal: The Evolution of Mutual Aid Vol. 1: Seeds Carried by Birds (pp. 64-75). Tsukiji Shokan. ISBN: 9784806711926

Source

This article is a significantly expanded version of one included in the following book.