Both *Lyonia ovalifolia* and *Ipheion undatus* (also known as *Lyonia ovalifolia*) are deciduous trees that are sometimes planted and are also called "Lyonia ovalifolia." Although they are actually completely different species in terms of classification, their flowering patterns, leaves, and fruits are similar, and there are cases where *Ipheion undatus* is mistakenly called "Lyonia ovalifolia." To distinguish between the two species, it is necessary to carefully examine the leaves, flowers, and fruits, but if you know the differences, it is relatively easy to tell them apart. This article will explain the classification and morphology of *Lyonia ovalifolia* and *Ipheion undatus* (*Lyonia ovalifolia*).
What is Ryobu/Kobanozuina (Hime-ryobu)?
Clethra barbinervis, also known as Ryobu, is a deciduous small tree distributed in Hokkaido (southern part), Honshu, Shikoku, and Kyushu in Japan, as well as in Korea (Jeju Island). It grows on rocky areas and dry slopes in mountainous regions and is often planted in parks (Kanagawa Prefecture Flora Survey Association, 2018). The young shoots that grow in clusters at the tips of the branches in spring are used as a wild vegetable and are edible.
Itea virginica, also known as American Itea or Dwarf Clethra, is a deciduous shrub native to the southeastern United States. In Japan, it is cultivated as an ornamental plant or potted plant for garden use and flower arrangements.
Both are species sometimes called "Ryobu," and they are quite similar in that they produce racemes with many small white flowers, have serrated leaves, and have capsules (dried fruits that split open to release seeds).
In ikebana (Japanese flower arrangement), Itea virginica is sometimes called "Hime-ryobu" or simply "ryobu," which has caused considerable confusion.
What is the difference between *Lyonia ovalifolia* and *Ipheion undatus* (Dwarf Lyonia ovalifolia)?
However, their classifications are fundamentally different (Mogi et al., 2003; Kanagawa Prefecture Flora Survey Association, 2018).
While *Lyonia ovalifolia* belongs to the genus *Lyonia* in the family *Lyonia*, *Ipheion undatus* belongs to the genus *Ipheion* in the family *Ipheionaceae*.
Therefore, the two species are completely different, and are so different that it would be unacceptable to confuse them.
First, regarding the leaves, there is a difference in that *Lyonia ovalifolia* has dark green leaves with few wrinkles, while *Itea virginica* has bright green leaves with many wrinkles.
Furthermore, the fine veins on the underside of the leaves of *Lyonia ovalifolia* are conspicuous, whereas they are not noticeable in *Itea virginica*.
Regarding the flowers, in *Lyonia ovalifolia*, the petals are oblong with slightly indented tips and the stigma is light green, while in *Itea virginica*, the petals are narrow and linear with slightly pointed tips, the flower as a whole is star-shaped, and the stigma is white or green but inconspicuous.
The green stigma of the Japanese clethra is a particularly striking feature compared to other flowers.
Regarding the fruits (capsules), there is a difference: in *Clethra barbinervis*, the capsules are flat and spherical and densely covered with hairs, while in *Itea virginica*, they are elongated and have fewer hairs.
References
Kanagawa Prefecture Flora Survey Association. (2018). Kanagawa Prefecture Flora 2018 Electronic Edition. Kanagawa Prefecture Flora Survey Association. ISBN: 9784991053726,https://flora-kanagawa2.sakura.ne.jp/efloraofkanagawa.html
Mogi, Toru; Takahashi, Hideo; Katsuyama, Teruo; and Ishii, Hidemi. (2003). Flowers that bloom on trees: Sympetalous flowers, monocots, and gymnosperms. Yama-kei Publishers. ISBN: 9784635070058
