Arisaema triphyllum

Native

Moist to moderate moisture. Woods. Partial sun to shade.

April to June

Yellow

12″ to 36″

This is a 12″ to 36″ tall, erect, perennial forb that rises from a corm with secondary roots.

There is no central stem.

Usually 2 leaves, sometimes just 1, rarely 3 rise from the corm on long, erect stalks that reach 24″ by the time the plant is in full flower. The leaves are divided into 3, rarely 5, more or less stalkless leaflets. The leaflets are 2½″ to 8″ long, 1¼″ to 5½″ wide, and taper gradually to a point at the tip with concave sides along the tip. There is a single prominent vein originating from the base of the leaf and extending to the tip. There are up to 10 or more prominent, parallel, lateral veins branching pinnately off the midvein. The lateral veins curve abruptly toward the leaf tip before reaching the margin, and join together in a marginal vein.

The upper surface is medium to dark green and hairless. The lower surface is paler green, hairless, and covered with a whitish, waxy coating (glaucous). The margins are untoothed. The terminal leaflet is egg-shaped or broadly diamond-shaped. The lateral leaflets are distinctly asymmetrical and smaller than the terminal leaflet.

A single flower stalk (peduncle) rises from the corm with the leaves. The peduncle is shorter than the leaf stalks.

The inflorescence is a spike with tiny flowers crowded on a thickened axis (spadix). The spadix is yellow, 1″ to 3½″ tall, blunt-tipped, and club-shaped, tapering slightly from a narrower base to a broader tip. A leaf-like bract (spathe) forms a tube surrounding the spadix. It is expanded near the tip forming a long, tapering hood that covers the spadix and tube. The hood opens at maturity, exposing half of the spadix. The spathe is green, often with purple stripes.

The male flowers are located above the female flowers on the lower half of the spadix. The upper part of the spadix has no flowers.

The fruit is a nearly spherical, 1 ⁄5″ to ¼″ long, red berry with 1 to 3 seeds, borne in a tight cluster up to 2″ long.

Trilliums (Trillium spp.) look similar when no flower or fruit is present. They can be distinguished from Jack-in-the-pulpit by the veins on the leaves. Trillium leaves have 5 prominent veins originating from the base of the leaf and extending to the tip. The lateral veins form a network.