Although these morphological forms may be recognizable in the field, distinguishing these differences in herbarium specimens is often difficult, and there is much overlap occurs in expression of the characteristics supposedly defining infraspecific taxa. Numerous intermediate forms exist, including putative hybrid populations be tween the subspecies with 2n = 42 (D. G. Huttleston 1949, 1953). Given these problems and the sympatric ranges of the 'subspecies' recognized by previous workers, A. triphyllum is treated here as one highly variable species. In addition to the above variability within the Arisaema triphyllum complex, putative hybrid populations between A. triphyllum and A. dracontium also occur naturally (L. L. Sanders and C. J. Burk 1992). These plants do not produce mature fruits but do reproduce vegetatively.
Perennial herb 15 cm - 0.9 m tall Leaves: usually two, long-stalked, with three leaflets (rarely five). The leaflets are more or less stalkless, to 30 cm long and 20 cm wide, with the terminal leaflet elliptic to broadly egg-shaped and the lateral leaflets somewhat asymmetrical and sometimes lobed or divided. Lower leaf surface glossy. Inflorescence: of many tiny flowers borne tightly clustered on the bottom half of a spike with a very fleshy axis (spadix), with male flowers above female flowers. The spadix is yellow, 3 - 9 cm long, and cylindric (rarely club-shaped) with a blunt tip. The leaf-like sheath (spathe) surrounding the inflorescence forms a fluted green tube sometimes striped with purple or white, having a rim 1 - 3 mm wide, and expanding near the tip to form a long tapering hood over the inflorescence. Fruit: a 6 - 15 mm long cluster of nearly spherical red berries, each with one to three seeds reaching 3 - 5 mm across.
Similar species: Arisaema triphyllum ssp. triphyllum differs from Arisaema triphyllum ssp. stewardsonii by having a whitish waxy coating on the lower leaf surface, a 4.9 - 9 mm wide spathe rim, a green spathe hood that sometimes has purple (but not white) stripes, and a usually club-shaped spadix tip. Its range is also widespread across the Chicago Region.
Flowering: mid April to mid July
Habitat and ecology: Swamps, marshes, floodplains, and moist areas.
Occurence in the Chicago region: native
Etymology: Arisaema comes from the Greek words aron, meaning Arum, and haima, meaning blood, referring to the blotchy red leaf color of some species. Triphyllum means three-leaved. Stewardsonii was named after Stewardson Brown (1867 - 1921), one of the plant's discoverers.
Corm very acrid; lvs mostly 2, the petiole 3-6 dm at anthesis, sometimes later to 15 dm; lfls 3, acuminate, the terminal elliptic to rhombic-ovate, the lateral often asymmetrical; veins of the lfls parallel from the midrib to the marginal vein, connected by numerous anastomosing veinlets; peduncle 3-20 cm; spathe convolute below, expanded above and arched over the spadix, abruptly acuminate; spadix cylindric or barely clavate, yellow, blunt; fr 1 cm; 2n=28, 56. N.S. to N.D., s. to Fla. and Tex. Spring. Four vars., 3 in our range, the fourth (quinatum) southern:
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.