Lactuca serriola

Native to Europe, Asia, northern Africa, and the Indian subcontinent. Introduced and naturalized in North America.

Roadsides, disturbed sites.

July to September

Yellow, drying to bluish-white

1′ to 5′

This is an erect annual or biennial with a thick, deep taproot. The stems and leaves contain a white milky latex.

The stems are unbranched except in the inflorescence. They are leafy and hairless, often with prickles near the bottom.

The leaves are alternate, stalkless, blue-green, and usually lobed. The basal lobes are angular and clasp the stem. They are up to 12″ long and 4″ wide near the base, becoming smaller as they ascend the stems. They are hairless but have prickles on the leaf margin. The midvein on the underside also has prickles. The leaves are often oriented in a flat, north-south plane.

The inflorescence is a long, spreading, cone-shaped, loosely-branched cluster with 13 to 27, usually 18 to 24, yellow flowers.

The flower heads are about ⅜″ across and have 12 to 20 yellow ray florets. The rays have truncated tips with 5 small teeth. They dry to a bluish-white.

The fruit is a pale grayish to tan achene with fluffy, white bristles attached to the tip.

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. There are no prickles on the midvein on the underside.

Tall blue lettuce (Lactuca biennis) has bluish to white flowers. The achene has grayish-brown bristles attached to the tip. There are no prickles on the midvein on the underside.

Woodland lettuce (Lactuca floridana var. floridana) has light blue flowers. There are no prickles on the midvein on the underside.