Lactuca biennis

Native

Moist. Thickets, stream banks, woods.

July to September

Bluish to white

2′ to 6½′

This is a 2′ to 6½′ tall, erect, annual or biennial forb with a thick, deep taproot. The stems and leaves contain a milky latex.

The stems are leafy and hairless.

The alternate leaves are lobed halfway or more to the midrib but not reaching the midrib. They are up to 4″ to 16″ long and 1½″ to 8″ wide. They are attached to the stem without a leaf stalk, with the base partly surrounding the stem (clasping). The main veins on the underside are hairy.

The inflorescence is a terminal tall, narrow, crowded cluster, and small clusters in the leaf axils.

The flower heads are about ⅜″ across and have 15 to 50, usually 20 to 30, bluish to white ray florets.

The fruit is a brown achene with fluffy, grayish-brown bristles attached to the tip.

Canada lettuce (Lactuca canadensis) has yellow flowers.

Prickly lettuce (Lactuca serriola) has yellow flowers. The leaves have prickles on the leaf margins and on the underside of the midvein.

The blue species of Lactuca are extremely variable and identifying characteristics overlap, factors which, taken together, make the species difficult to separate.

Showy blue lettuce (Lactuca tatarica ssp. pulchella) has large, showy flower heads that measure, ¾″ across. The achene has white bristles attached to the tip.

Woodland lettuce (Lactuca floridana var. floridana) has a more open inflorescence and tends to be less leafy than tall blue lettuce. The flower heads have 10 to 15 ray florets. The achene has white bristles attached to the tip.