Both Ouja (Japanese jasmine) and Oujamodoki (Yunnan jasmine) belong to the genus Jasminum in the family Oleaceae, and are native to China, cultivated for ornamental purposes. Their distinctive feature is the yellow flowers that bloom even in winter, which is likely one of the reasons for their popularity. However, they share many similar characteristics, so many people may confuse them. The most significant difference is that Ouja is deciduous, while Oujamodoki is evergreen, but practically speaking, checking the condition of the leaf hairs might be the easiest way to distinguish them. While the name and wintersweet (Chimonanthus praecox) are the same and both bear yellow flowers in winter, they are otherwise completely different. This article will explain the classification and morphology of Ouja and Oujamodoki.

What are *Jasminum humile* and *Jasminum humile* (Yunnan jasmine)?

The yellow jasmine (Jasminum nudiflorum) is a deciduous shrub native to northwestern China and Tibet, growing in bushes, valleys, and slopes (Wu & Raven, 1996; Hayashi, 2019). It is cultivated as an ornamental plant worldwide, including in Japan, and is used as a garden tree and potted plant.

Jasminum mesnyi, also known as Yunnan jasmine, is an evergreen shrub native to southern China and Vietnam, growing in valleys and forests. It is cultivated as an ornamental plant worldwide, including in Japan, and is used as a garden tree and potted plant.

Both belong to the genus Jasminum in the family Oleaceae, and are native to China, cultivated as ornamental trees. Their distinctive feature is the yellow flowers that bloom even in winter, which is likely another reason for their popularity.

The genus Jasminum belongs to the group commonly known as "jasmine," and as exemplified by Jasminum grandiflorum, the flowers and essential oils often have a pleasant scent. However, Oujas japonica and Oujas mimosa do not have such a scent.

Furthermore, regarding leaf shape, while Jasminum species often have odd-pinnately compound leaves, Forsythia suspensa and Forsythia jasminoides have trifoliate compound leaves, meaning that a single leaf has been divided into three.

Because of these characteristics, Ouja and Oujamodoki are very similar, as their names suggest, and many people may confuse them.

What is the difference between *Jasminum nigrum* and *Jasminum yunnanense* (false *Jasminum yunnanense*)?

The two species are quite similar, but they can be distinguished by careful observation (Wu & Raven, 1996; Hayashi, 2019).

First, there is a difference in that Ouja (Japanese jasmine) is a deciduous shrub, while Oujamodoki (false Ouja) is an evergreen shrub.

Therefore, while the common winter jasmine loses its leaves in winter, the false winter jasmine retains its leaves. The leaves of the false winter jasmine are also somewhat stiff, as is typical of evergreen trees.

Since the flowering period for Ouja (Northern Jasmine) is from February to April, and for Oujamodoki (False Northern Jasmine) it is from March to May, you can observe Ouja with only flowers from winter to spring, but you can observe Oujamodoki with both leaves and flowers at the same time.

There are other differences in the leaves as well. In *Ouja*, the entire surface is covered with many short hairs, giving it a bumpy appearance, while in *Ouja-modoki*, there are fewer short hairs, only minute ones on the leaf edges.

Regarding the flowers, there is a difference between *Oubai* (Winter Jasmine) and *Oubaimodoki* (False Winter Jasmine), which have corollas that are about 3 cm in diameter and have 6 to 8 lobes, or even more, double corollas that are about 4 cm in diameter.

The above will allow you to distinguish them reliably. Incidentally, while *Jasminum nigrum* is also a member of the *Jasminum* genus and has yellow leaves, its leaves are odd-pinnately compound.

What is the difference between Oubai (yellow jasmine) and Chimonanthus praecox (winter jasmine)?

Some people might be curious about the difference between winter jasmine (Chimonanthus praecox) and winter sweet (Chimonanthus praecox), which, like winter jasmine, bears yellow flowers in winter.

However, winter sweet (Chimonanthus praecox) belongs to the Calycanthaceae family, and its body structure is quite different from that of the Oleaceae family (Chimonanthus praecox).

Regarding the leaves, there is a difference in that *Oubai* has trifoliate compound leaves, while *Chimonanthus praecox* has simple leaves.

Regarding the flowers, there is a difference in that the flower tubes of the winter jasmine are long and the flowers bloom to the side or diagonally downwards, while the flowers of the winter jasmine lack flower tubes and bloom directly downwards towards the ground.

Regarding the fruit, there is a difference between the two: the winter jasmine (Chimonanthus praecox) produces red, ripe drupe-like berries (fruits that turn into liquid) that are eaten by birds, while the winter jasmine (Chimonanthus praecox) produces fruits encased in large, black, vase-like pseudocapsules that simply fall off due to gravity.

What are the differences between wintersweet (Chimonanthus praecox) and wintersweet (Chimonanthus praecox var. japonica)? Is it poisonous? Is there a reason why wintersweet flowers bloom in the middle of winter? The wintersweet's minority strategy!

Wintersweet (Chimonanthus praecox) is native to China and is used as a garden tree in Japan. Although not widely known, its seeds and leaves are poisonous, so caution is necessary. Wintersweet and Chimonanthus praecox can be distinguished by the color of their flowers. Wintersweet blooms in the middle of winter, when other plants are not in bloom...

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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

Wu, ZY, & Raven, PH 1996. Flora of China (Vol. 15 Myrsinaceae through Loganiaceae). Science Press, Beijing, and Missouri Botanical Garden Press, St. Louis. 387pp. ISBN: 9780915279371

The Calycanthaceae family consists of fragrant, deciduous shrubs reaching 2-4 meters in height, with the exception of Idiospermum, which grows into a large evergreen tree. It comprises 3 genera and 10 species, and its distribution is limited to warm temperate and tropical regions. These include: Calycanthus (3 species; 1 species in western and southeastern North America and eastern Asia); Chimonanthus (6 species; East Asia); and Idiospermum (1 species; Queensland, Australia). The flowers range in color from white to red, with petals arranged spirally. Based on DNA phylogenetic trees, Calycanthus and Chimonanthus in the Northern Hemisphere diverged in the Middle Miocene, but Idiospermum in Australia had already diverged by the Upper Cretaceous. The discovery of Cretaceous Calycanthaceae fossils in Brazil suggests a likely remnant of a former Gondwanan distribution that included South America.

This article provides a comprehensive, field guide-style introduction to plants belonging to the Calycanthaceae family.

The basic information is based on Hayashi (2014). Photos are replaced as better ones become available. Also, while the identification is done by the author, please note that it may be changed without notice if there are any misidentifications.

No. 0136 Chimonanthus praecox

Deciduous shrub. Leaves are 8-20 cm long, with the widest part near the base to the middle. Petioles are 3-8 mm long. The leaves are large and long ovate, with a rough surface. It is easy to identify because there are few trees with large, entire leaves growing opposite each other. The sac-like fruits, about 4 cm long, that remain on the branches for a long time are also a good indicator. The flowers are yellow and bloom from December to February. The tree grows to a height of 2-5 m. Native to China. Commonly used as a garden tree and park tree.

What are the differences between wintersweet (Chimonanthus praecox) and wintersweet (Chimonanthus praecox var. japonica)? Is it poisonous? Is there a reason why wintersweet flowers bloom in the middle of winter? The wintersweet's minority strategy!

Wintersweet (Chimonanthus praecox) is native to China and is used as a garden tree in Japan. Although not widely known, its seeds and leaves are poisonous, so caution is necessary. Wintersweet and Chimonanthus praecox can be distinguished by the color of their flowers. Wintersweet blooms in the middle of winter, when other plants are not in bloom…

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No.0136.1 Chimonanthus praecox f. concolor

This is a variety of winter sweet (Chimonanthus praecox) with yellow inner petals. It has become widely planted in recent years.

What are the differences between wintersweet (Chimonanthus praecox) and wintersweet (Chimonanthus praecox var. japonica)? Is it poisonous? Is there a reason why wintersweet flowers bloom in the middle of winter? The wintersweet's minority strategy!

Wintersweet (Chimonanthus praecox) is native to China and is used as a garden tree in Japan. Although not widely known, its seeds and leaves are poisonous, so caution is necessary. Wintersweet and Chimonanthus praecox can be distinguished by the color of their flowers. Wintersweet blooms in the middle of winter, when other plants are not in bloom…

ecological-information.com

References

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

Wintersweet (Chimonanthus praecox) is native to China and is used as a garden tree in Japan. Although not widely known, its seeds and leaves are poisonous, so caution is necessary. Wintersweet and Chimonanthus praecox can be distinguished by the color of their flowers. Wintersweet blooms in the middle of winter, brightening up gardens when other plants are not in bloom, but do you know why wintersweet does this? Although not well known in Japan, it has been studied in China and it has been found that wintersweet differentiates itself from other plants by relying on flies that can be active even in winter for pollination. This article will explain the classification, toxicity, history, pollination ecology, and seed dispersal of wintersweet.

A deciduous shrub native to China.

Chimonanthus praecox, also known as winter sweet, is native to China and cultivated in temperate regions, including Japan (Wu et al., 2008). In China, it is a deciduous shrub that grows in mountainous forests.

It belongs to the genus Chimonanthus in the family Calycanthaceae. Its leaves are petiolate and opposite, about 15 cm long, ovate or ovate-elliptic in shape, pointed at both ends, with entire margins and a rough surface.

[Seed Plant Encyclopedia #033] What are the species of the Calycanthaceae family? Photo list

The Calycanthaceae family consists of fragrant, deciduous shrubs reaching 2-4 meters in height, with the exception of Idiospermum, which grows into a large evergreen tree. It comprises 3 genera and 10 species, and its distribution is limited to warm temperate and tropical regions. Calycanthus (3 species; western North America...).

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The little-known toxicity of winter sweet

Although not widely known, wintersweet is poisonous.

Seeds and leaves are known to contain calycanthine, a type of alkaloid (Haruyama, 2020).

When animals ingest calicanthine, the release of GABA, an inhibitory neurotransmitter in the central nervous system, is inhibited, and the release of dopamine increases, leading to tonic seizures and tachypnea.

In 2016, sheep grazing in Japan actually ingested winter sweet seeds and suffered from poisoning symptoms. However, there are currently no known cases of this affecting humans.

There are significant differences between animal species and individual plants, and the exact level of toxicity is currently unknown, but it's best to avoid intentionally ingesting the leaves or seeds.

When did winter sweet (Chimonanthus praecox) arrive in Japan?

The name " Chimonanthus praecox" already appears in the "Onko Chishinsho," a Japanese dictionary compiled in 1484 during the late Muromachi period. Therefore, it is believed to have been introduced to Japan around this time (Isono, 2007). However, there are no further records of it for some time after that.

Winter sweet (Chimonanthus praecox) reappears in the early Edo period in 1666 in a picture scroll by Kano Tsunenobu, a painter of the Kano school, and in 1674 in Kano Tan'yu's "Illustrated Scroll of Flowers and Plants," suggesting that it may have actually become popular from this period onward.

Since then, various crossbreedings have been carried out, and breeding efforts have progressed (Haruyama, 2020). In Japan, it is mainly cultivated in farms and gardens for ornamental purposes.

Are the red parts on the petals of this flower, which blooms in the middle of winter, meant to attract insects?

In the depths of winter, from January to February, glossy yellow flowers bloom facing downwards before the leaves appear. The petals are arranged in a ring, overlapping in several layers. The outer petals are nearly oblong, becoming more oval towards the center. The inner petals are purplish-red and secrete nectar (Hirono, 2017). This is thought to make it easier for insects to find the nectar. However, in Chimonanthus praecox f. concolor, the petals are yellow.

A minority strategy to bloom in winter

It seems strange that these flowers bloom in the middle of winter when insect activity is very low, doesn't it? This is something that doesn't receive much attention in Japan, but it's very unique. What kind of insects visit them at this time of year?

Independent studies were conducted in Wuhan, Hubei Province, and Nanjing, Jiangsu Province, China, and the results showed that in both locations, hoverflies, flies, and Italian honeybees (Western honeybees) were the main visitors (Lihua et al., 2006; Du et al., 2012).

However, it was found that hoverflies do not carry pollen, and Italian honeybees do not come in large numbers, so in effect, only flies are responsible for pollination.

Flies are more tolerant of cold than other insects. It is thought that winter sweet flowers bloom in winter when other flowers are absent, thus ensuring that flies carry out pollination.

The fruit is encased in a false fruit!?

After flowering, the plant develops fruit, but the way it forms is unusual.

In wintersweet, the fleshy receptacle that holds the fruit enlarges, forming a false fruit. Its appearance is resembling a vase.

The false fruit contains 5 to 20 true fruits (achenes), each containing a seed. When the false fruit ripens, it splits open at the base, and the true fruits are dispersed by gravity (Yang et al., 2013).

References

Du, W., Wang, S., Wang, M., & Wang, X. 2012. Who are the major pollinators of Chimonanthus praecox (Calycanthaceae): insect behaviors and potential pollination roles. Biodiversity Science 20(3): 400-404. ISSN: 1005-0094, https://doi.org/10.3724/SP.J.1003.2012.05033

Haruyama, Yui. 2020. Suspected cases of winter jasmine poisoning in sheep. Journal of the Japan Veterinary Medical Association 73(5): 249-252. ISSN: 0446-6454, https://doi.org/10.12935/jvma.73.249

Isono, Naohide. 2007. Chronological Table of Horticultural Plants Introduced to Japan Before the Meiji Era. Keio University Hiyoshi Journal, Natural Sciences 42: 27-58. ISSN: 0911-7237, https://koara.lib.keio.ac.jp/xoonips/modules/xoonips/detail.php?koara_id=AN10079809-20070930-0027

Ikuo Hirono. 2017. You can't really tell what winter sweet flowers are just by looking at them! Continued: A Walk Through the Trees 231. Tree Notebook. https://kinomemocho.com/sanpo_Chimonanthus.html

Lihua, Z., Riming, H., & Jianzhong, W. 2006. The pollination biology of Chimonanthus praecox (L.) Link (Calycanthaceae). Acta Horticulturae Sinica 33(2): 323-327. https://www.ahs.ac.cn/EN/Y2006/V33/I2/323

Wu, X., Raven, PH, & Hong, D. (Eds.). 2008. Flora of China (Vol. 7 Menispermaceae through Capparaceae). Science Press, Beijing, and Missouri Botanical Garden Press, St. Louis. xii, 499pp. ISBN: 9781930723818

Yang, J., Dai, P., Zhou, T., Huang, Z., Feng, L., Su, H., … & Zhao, G. 2013. Genetic diversity and structure of wintersweet (Chimonanthus praecox) revealed by EST-SSR markers. Scientia Horticulturae 150: 1-10. https://doi.org/10.1016/j.scienta.2012.11.004

Source

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