Arisaema triphyllum

Copyright: Flora of North America Association

Plants 1.5-9dm. Roots radiating from apex of form; corm to 8 cm diam. Leaves 1-2 (-3); petiole green, purple-marked, or purple; blade palmately divided; leaflets 3 (-5), sessile or short-petiolulate, elliptic to broadly ovate, to 30 × 20 cm, apex obtuse or acute to acuminate; lateral leaflets often asymmetric, sometimes lobed or divided. Inflorescences: spathe convolute basally, 6-16 cm; tube green, sometimes striped or variously marked with purple or white; blade outside green, often with purple or white, inside varying from uniformly green to purple, or variously striped, forward-curving, forming hood over tube, broadly ovate to lanceolate, apex acute to long-acuminate; spadix 3-9cm, shorter than spathe, apex blunt. Staminate flowers with 3-5 stamens. Fruits widely obovoid to obconic, 6-15 mm. Seeds 1-3 (-6), 3-5 mm diam. 2n = 28, 42, 56.

Phenology: Flowering early–late spring.
Habitat: Moist to dry deciduous woods and thickets, bottoms, swamps, and bogs.
Elevation: 0–2000 m

Man., N.B., N.S., Ont., P.E.I., Que., Ala., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Okla., Pa., R.I., S.C., S.Dak., Tenn., Tex., Vt., Va., W.Va., Wis.

Discussion

Considerable diversity of opinion exists as to the delimitation of taxa and application of names in the Arisaema triphyllum complex. Three subspecies are recognized in the most recent study of this group (M. Treiber 1980): subsp. triphyllum, subsp. pusillum, and subsp. stewardsonii. This treatment of infraspecific taxa is essentially in agreement with that of the previous revision of the complex (D. G. Huttleston 1949, 1953, 1981), except for A. triphyllum subsp. quinatum (Nuttall) Huttleston, which is regarded by Huttleston as a distinct subspecies and is included in subsp. pusillum by Treiber.

As defined by Treiber (1980), Arisaema triphyllum subsp. triphyllum is a widespread tetraploid (2n = 56) ranging from Gaspé Peninsula to Manitoba and North Dakota south to central Florida and eastern Texas. The distribution of A. triphyllum subsp. pusillum, a diploid (2n = 28), approaches that of subsp. triphyllum except in the northeast and midwest, where it is uncommon. Arisaema triphyllum subsp. stewardsonii, also a diploid, has the most restricted range of the three subspecies and is found primarily in the northeastern United States ranging south along the mountains to North Carolina and Tennessee. In addition to having a restricted range, subsp. stewardsonii is also restricted in habitat and grows primarily in swamps, marshes, floodplains, and other moist areas. The other two subspecies, especially subsp. triphyllum, grow in a broad range of habitats. Sympatric populations of the different subspecies occur.

Distinguishing characteristics of Arisaema triphyllum subsp. triphyllum include leaves that are abaxially glaucous, a club-shaped (rarely cylindric) spadix appendage, and 4.5-9.5 mm wide spathe flanges. The other two subspecies have leaves that are not abaxially glaucous, spathes with narrower flanges (1-3 mm wide), and a cylindric (rarely club-shaped) spadix appendage. Arisaema triphyllum subsp. stewardsonii is distinguished primarily by its strongly fluted or ribbed spathe tube and a spathe hood that is usually green with white or purple stripes. The spathe tube of A. triphyllum subsp. pusillum is at most weakly fluted, and the spathe hood is usually uniformly green or purple.

Although these subspecies are not recognized here, the following key (M. Treiber 1980) is provided for those wishing to determine plants at the infraspecific level.

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.

Selected References

None.

Lower Taxa