Platyosprion platycarpum (Maxim.) Maxim. — False-yellowwood

Introduction

False-yellowwood (Platyosprion platycarpum) is a deciduous forest tree native to southern China, South Korea, and Japan. Mature trees can reach about 30 m. Leaves usually contain around 13 leaflets, with a broader observed range of about 7–15; small stipels are normally present at the leaflet bases. Erect terminal panicles bear relatively small white flowers, about 1 cm across, from April through June. The mature legumes are flattened and conspicuously winged along both margins, the most immediately useful distinction from true yellowwoods (Cladrastis) (Flora of China Editorial Committee 2010; Johnson 2021).

The species inhabits forests on valleys and slopes, particularly below about 1000 m. Despite the common name “Japanese false-yellowwood,” the species has a broad East Asian range and is native well beyond Japan. Indeed, this geographic variation has resulted in several localized variants that are currently united under a single species concept, but certainly worthy of recognition as a species complex. Tree TSAR uses false-yellowwood as its preferred common name while retaining Japanese yellowwood, fujiki, and yama-enju as searchable historical or vernacular alternatives.

For more than a century the species was commonly known as Cladrastis platycarpa, but modern phylogeny places it outside Cladrastis sensu stricto. Current consensus on classification returns the species to Platyosprion, a generic concept Maximowicz had already recognized in the nineteenth century (Duan et al. 2019; International Plant Names Index 2026).

One species from a historically divided complex

Tree TSAR follows the integrative treatment of Duan et al. (2019) in accepting a single species in Platyosprion. The names Cladrastis chingii, C. parvifolia, C. scandens, and C. yungchunii are all retained in synonymy rather than recognized as separate species. The conclusion was based not on one character or one gene tree but on combined phylogenetic, morphological, occurrence, and ecological evidence. Current Plants of the World Online follows the same one-species treatment and additionally places Cladrastis platycarpa var. parvifolia in synonymy (Duan et al. 2019; Royal Botanic Gardens, Kew 2026).

The former segregates illustrate different ways apparent species boundaries can arise. C. scandens was described as a woody climber, but field investigation indicated that the supposed climbing habit reflected juvenile false-yellowwood rather than a separate liana species. C. parvifolia was based largely on reduced leaf and inflorescence dimensions that did not define a coherent independently supported lineage. Characters once used for C. chingii, including stipel and fruit differences, proved less consistent when mature and additional material was examined (Duan et al. 2019).

Cladrastis yungchunii deserves the greatest continuing attention within this synonym complex. It was described from western portions of the Chinese range and differs in features including unusually glabrous foliage and reduction or absence of the stipels typical of false-yellowwood. Available molecular and ecological evidence nevertheless places it within P. platycarpum, and collections remain sparse. Tree TSAR therefore retains yungchunii in synonymy while treating geographically dense population sampling of that lineage as the principal future species-boundary test. This uncertainty concerns structure within P. platycarpum and does not weaken recognition of Platyosprion as a genus (Duan et al. 2019).

Horticultural and Agricultural Uses

False-yellowwood remains uncommon in gardens, but genuine specimens in European and North American arboreta demonstrate considerable ornamental potential. The species develops a domed crown, smooth gray bark, elegant pinnate foliage, erect white flower clusters, distinctive winged fruits, and attractive autumn color. Documented cultivated trees suggest hardiness around USDA Zone 5b, although performance varies with provenance and site (Johnson 2021).

Well-drained, reasonably fertile soils with consistent moisture suit its forest origin, and cultivated experience indicates tolerance of neutral to alkaline conditions. False-yellowwood also leafs out appreciably earlier than C. delavayi, a useful distinction where the two are grown together. Seed propagation has proved straightforward in botanical collections, but the species remains much less available commercially than its ornamental qualities would suggest (Johnson 2021).

Historical labeling requires caution. Genuine false-yellowwoods have persisted under the old name Cladrastis platycarpa, while some trees bearing that label have proved to be Styphnolobium japonicum or other unrelated look-alikes. Verified provenance and mature fruit are particularly valuable for confirming cultivated material.

Conservation Concerns

False-yellowwood is currently assessed as Least Concern. Its native range spans southern China, South Korea, and Japan, and Kew’s current data also classify it as confidently not threatened in global extinction-risk prediction (Royal Botanic Gardens, Kew 2026).

The broad species concept should not, however, erase geographic diversity within the range. The poorly collected yungchunii component illustrates how population structure may remain hidden inside a species that is secure globally. Range-wide sampling, especially from geographically or morphologically distinctive Chinese populations, would clarify whether the present one-species treatment conceals independently evolving local lineages.

Because P. platycarpum is the sole surviving species of Platyosprion, preserving representative populations across China, Korea, and Japan also preserves the full living diversity of an ancient genus.

Additional Information

iNaturalist (opens in a new tab): Active species concept now follows Platyosprion platycarpum; iNaturalist transferred records from the former Cladrastis platycarpa concept in 2025.
Plants of the World Online (opens in a new tab): Accepted taxonomy, China–Korea–Japan range, synonymy, and global conservation information.
Trees and Shrubs Online (opens in a new tab): Detailed morphology, identification, cultivation history, and known living specimens.
Flora of China (opens in a new tab): Morphology and habitat under the former name Cladrastis platycarpa and an older, more finely split species concept.
International Plant Names Index (opens in a new tab): Nomenclatural link from Sophora platycarpa to Platyosprion platycarpum.

References and Further Reading

Duan L, Harris AJ, Ye W, Deng S-W, Song Z-Q, Chen H-F, Wen J (2019) Untangling the taxonomy of the Cladrastis clade (Leguminosae: Papilionoideae) by integrating phylogenetics and ecological evidence. Taxon 68(6): 1189–1203. DOI 10.1002/tax.12155 (opens in a new tab).

Flora of China Editorial Committee (2010) Cladrastis platycarpa. In: Wu ZY, Raven PH, Hong DY (eds) Flora of China, Vol. 10. Science Press, Beijing & Missouri Botanical Garden Press, St. Louis.

International Plant Names Index (2026) Platyosprion platycarpum (Maxim.) Maxim. International Plant Names Index.

Johnson O (2021) Platyosprion platycarpum. Trees and Shrubs Online.

Royal Botanic Gardens, Kew (2026) Platyosprion platycarpum (Maxim.) Maxim. Plants of the World Online.