1. Arum italicum Mill. ssp. italicum (Italian arum)

Map 100

Plants with horizontal, rhizomelike tubers, sometimes forming clumps. Leaves 25B75 cm long, continuing to enlarge during growing season, glossy, the blade sagittate or hastate, with 3 distinct main veins (the 2 lateral ones running into the basal lobes), green with usually white or lighter green along the larger veins. Lateral veins forming a complex network over the entire leaf surface. Spathes 10B30 cm long, pale green to nearly white, sometimes faintly purplish tinged near the base, the open part above the pistillate flowers withering as the fruits develop. Spadices yellow, with a thickened, sterile tip, the staminate flowers in the upper 25B35 percent of the flowering portion. Fruits 5B11 mm in diameter, orangish red to red at maturity, with 2B5 seeds, in a globose cluster, not enclosed in the spathe. 2n=84. MayBJune.

Introduced, known only from a single population in Poplar Bluff, Butler County (native of Europe, Asia, Africa, widely cultivated and sporadically escaped in the western U.S.). Mesic upland forests in rich soil at bottom of ravines.

Italian arum is a common ornamental in gardens. The Missouri population undoubtedly became established from tubers or seeds that were washed into a ravine from a housing development along the adjacent ridge. It was first reported by Hudson (1996), who observed the presence of numerous juvenile plants and at least some seed production.

Arum italicum contains four subspecies (Boyce, 1993), of which only ssp. italicum has the leaves with white mottling along the larger veins. The other subspecies are regional endemics within portions of the species= native range.