Trillium smallii is a species of flowering plant in the family Melanthiaceae. It is native to Japan and Sakhalin. It is a rhizomatous geophyte that grows primarily in temperate regions.

Description

Trillium smallii is a glabrous, rhizomatous perennial with erect stems 20–40 cm tall. It has three sessile, depressed rhombic-orbicular leaves, 7–17 cm long and about as wide. The flowers are ascending to horizontal at anthesis and become erect in fruit. The sepals are green or purple-brown, while the petals are usually absent or occasionally 1–3 and small, purple-brown. The fruit is a globose berry about 1–1.2 cm in diameter containing many seeds.

Distribution and habitat

The species is native to southern Sakhalin and northern to north-central Japan. It grows in woodland foothills and flowers from April to May. Populations studied in Hokkaido occur in temperate deciduous forest habitats.

Reproductive biology

Trillium smallii was included in a comparative study of four Japanese Trillium species by Masashi Ohara and Shoichi Kawano. The authors found that, despite differences in ploidy level, the species shared broadly similar reproductive traits. In that study, T. smallii had a mean seed weight of 4.47 mg, the highest reported among the four species examined. Mean seed production was reported as 104.3 and 113.0 seeds per plant in two sampling periods, with estimated seed-setting rates of 48.34% and 52.29%, respectively.

Cytogenetics

Trillium smallii is a hexaploid species with a chromosome number of 2n = 30.

Taxonomy

The species was first published by Carl Maximowicz in 1883. It has long been regarded as a species of hybrid origin in the Japanese botanical literature.

A 2006 study by Shosei Kubota, Yoshiaki Kameyama, and Masashi Ohara reexamined relationships among Japanese Trillium species using genetic and chromosomal data.

The study found that T. smallii is most closely related to Trillium apetalon and Trillium camschatcense, rather than to Trillium tschonoskii as suggested by earlier interpretations. Chloroplast DNA evidence also indicated affinity with T. camschatcense.

Based on these results, the authors concluded that T. smallii likely originated through hybridization and represents an allopolyploid derived from Trillium yezoense.