Vitex rotundifolia

Vitex rotundifolia, the roundleaf chastetree or beach vitex is a species of Vitex that is native to seashores throughout the Pacific. Its range includes continents and islands stretching from India east to Hawaii and from Korea south to Australia. This woody perennial plant typically grows approximately 1 m in height. It has a sprawling growth habit and produces runners that root regularly at nodes. This rooting pattern allows the plant to spread rapidly. At maturity, V. rotundifolia produces blue-purple flowers that are borne in clusters and ultimately yield small brown-black fruits. Its leaves are rounded at the tips with green upper surfaces and silver lower surfaces. While the plant is a seashore obligate, it grows over a wide latitude range. It has been used for medicinal purposes throughout its native range. More recently, it was imported to the eastern United States where it has become a seashore invasive. Control efforts are presently underway to protect the fragile beach dune ecosystem. Vitex rotundifolia is a sprawling shrub that can grow as tall as 1.5 m though it typically ranges from 0.5 to 1 m in height. As a product of its rapid nodal rooting, the plant can form dense mats reaching in excess of 10 m from the parent plant. New stems are green, square and fleshy initially before maturing brown and woody. Older, large-diameter stems are covered with heavily fissured bark. Running horizontal stems produce frequent upright branches. Leaves are strongly aromatic, intensifying when crushed. The majority of leaves are simple, but they can occasionally be palmate trifoliate or 2-leaved. Leaves measure 2 to 6.5 cm in length and 1-4.5 cm in width. Leaf margins are entire. The leaf shape varies from ovate to obovate with acute bases and obtuse apexes. Occasionally, leaf apexes are acute or emarginate. Upper leaf surfaces are dark green whereas lower leaf surfaces range in color from silver to white to light green; all leaf surfaces are tomentose. Petiole bases are typically somewhat purple and measure 0 to 1 cm in length. Blades are cupped downward slightly. Leaf veins are lighter green than surrounding tissue. Flowers are borne in indeterminate panicles that may be terminal or axillary. Infloresences measure 3 to 7 cm in length. The calyx is cup-shaped and 4 to 4.5 cm long. Flowers are zygomorphic, purple to blue-purple, and short pedunculate. They are two-lipped and funnel-form (measuring 8 mm in length). Four stamens are didynamous and extend beyond the corolla tube (measuring 9 to 10 mm). The style extends beyond the stamens (total length: 12 mm). Pollen is tricolpate. Ovaries consist of two carpels with each containing two single seeded locules. Fruits are globose drupes that are green while immature but turn yellow and red before maturing to bluish black. The fruits are frequently incorrectly characterized in the literature as 'seeds or berries'. Each drupe contains a maximum of four seeds though there are usually fewer as a result of seed abortion. Each seed is encapsulated in a separate compartment. Endosperm is absent. Seeds germinate into tender seedlings that bear two cotyledons and quickly develop two red-margined true leaves. Ploidy level is 2n = 32, 34*. Vitex rotundifolia is a member of the family Lamiaceae and subfamily Viticoideae. The plant was originally described by the son of Carl Linnaeus, Carl Linnaeus the Younger The original description was published in Supplementum Plantarum in 1782. The generic epithet, Vitex, is derived from the Latin viere, meaning “to bind or twist” in reference to the rope-like stems produced by some species in the genus. The specific epithet, rotundifolia, is derived from the Latin rotundus, which means 'round, spherical', and folium, meaning 'leaf.” This is a reference to the rounded character of the leaves. Vitex and all other members of the family Verbenaceae save those in the subfamily Verbenoideae were recently moved to the family Lamiaceae. As a result of this reorganization, two monophyletic families were established from the paraphyletic Verbenaceae and polyphyletic Lamiaceae. This new classification scheme was initially proposed by Cantino in 1992. Subsequent cpDNA analysis, rbcL sequence analysis, chemotaxonomic studies, and morphological analyses have supported the original logic for family reorganization. This revision has resulted in some confusion regarding the classification of V. rotundifolia in the literature. Despite the fact that the revision is well supported with volumes of data, many authors continue to incorrectly place the plant in Verbenaceae. Recent revisions of the genus Vitex have placed V. rotundifolia in synonymy with V. trifolia subsp. littoralis Steenis. Previous researchers have placed V. rotundifolia within V. trifolia. Moldenke (1958) placed V. rotundifolia in synonymy with V. trifolia var. simplicifolia. The placement of Moldenke was in disagreement with Corner (1939), which held V. rotundifolia as distinct from V. trifolia. The placement of Corner was subsequently supported by several authors: Fosberg (1962), Munir (1987), and Wagner (1999). Likely due to the wide range over which V. rotundifolia is native, the plant has acquired a host of common names. English speaking countries