*Citrus trifoliata Linnaeus. Trifoliate Orange, Hardy Orange. Phen: Mar-Jun; Sep-Oct. Hab: Bottomland and riparian forests, mesic upland forests, stream banks, spring runs, fencerows, roadsides, becoming common especially in suburban areas. Dist: Native of temperate China. See Nesom (2014a) for a detailed discussion of various aspects of this species in the se. United States.

Origin/Endemic status: E. and se. Asia

Taxonomy Comments: Citrus trifoliata is often placed in a separate genus, Poncirus, but differs very little from Citrus morphologically, has been shown to be phylogenetically nested within Citrus (Araújo, Queiroz, & Machado 2003), and thus seems best included in Citrus.

Other Comments: Planted in our area as an ornamental, as a "living fence", and also used as a grafting stock for citrus, C. trifoliata is a small tree or shrub that seems to be made up almost entirely of "thorns" (actually, stipular spines). The fruits closely resemble an orange, but are small (ca. 4 cm in diameter), densely pubescent, and sour.

Synonymy: = Ar, K3, Tx, Va, Araújo, Queiroz, & Machado (2003), Nesom (2014a); = n/a – C, Tat; = Poncirus trifoliata (L.) Raf. – F, Fl4, G, Il, K1, NcTx, Pa, RAB, S, Tn, WH3

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