[Non-native Lettuce: The Genus Lactuca in the Columbia River Gorge of Oregon and Washington]

Prickly Lettuce

Lactuca serriola

Synonyms: Lactuca scariola, Lactuca scariola var. integrata, Lactuca scariola var. scariola

Additional close-ups (from left to right) of the flower head, overlapping involucral bracts, and prickly, lobed leaves of prickly lettuce on the side of Forest Service Road 16 east of Big Creek in Logan Valley, Malheur National Forest...........August 20, 2011.

Characteristics:

Also known as China lettuce or wild lettuce, prickly lettuce is a somewhat weedy biennial or winter annual with a stout main stem arising from 30-150 cm high. The juice from the stem is milky, hence the genus name of Lactuca. The stem is generally unbranched below and may only have some side branches in the flowering portion of the stem. The alternate leaves are twisted at their base so as to lie in a vertical plane. Two earlike lobes at the base of the leaf clasp the stem. The midribs on the undersides of the leaves are coverd with prickles and the margins have finer prickles. The margins are pinnaely lobed. Individual leaves mesure from 5-30 cm long and 1-10 cm broad.

The numerous flower heads are found at the top of the plant. individual heads are 13-27 flowered, the rays yellow and often drying bluish. The involucre ranges from 10-15 mm high in fruit. Individual mature flower heads contain 6-30 flattened fruits with 5-7 parallel ridges on each side. The fruits are bristly near their summits.

This species may hybridize with domestic lettuce.

Habitat:

Prickly lettuce is a weedy species of fields and waste places. It is a serious weed in disturbed soils around irrigated crops and in orchards.

Range:

Native to Europe, prickly lettuce may now be found in disturbed places across North America.

It is found throughout the length of the Columbia River Gorge between the elevations of 100-1600 ft..

Paul Slichter