Appearance

Mycelis muralis is a slender, glabrous, herbaceous plant. It is annual to biennial depending on the habitat. Stems are erect, 2-3 ft. (0.6-0.9 m) tall, branched above and may one or more stems from a fibrous root. The stem surface is glabrous, often glaucous, and exudes milky juice when broken.

Foliage

Basal and lower stem leaves are 2.5-7 in. (6.4-17.8 cm) long, 1-3 in. (2.5-7.6 cm) wide, glabrous and deeply lobed, with broad, terminal segments. Leaf base is auriculate (lobed). The few middle and upper stem leaves are reduced in size.

Flowers

Each flower head is comprised of 5 yellow, strap-shaped ray florets.

Fruit

Achenes are approximately 0.13 in. (0.33 cm) long, several-nerved, and black or brown with white pappus that may disperse seeds long distances by wind.

Ecological Threat

Mycelis muralis reproduces exclusively by seed. A plant may produce up to 500 seeds in shaded sites and up to 11,500 seeds in open sites. Wall lettuce can grow in deep shade and full sun. It is adapted to a range of soil conditions. It readily invades disturbed habitats.

Selected Images

Maps

Invasive Listing Sources

• Massachusetts Invasive Plants Advisory Group List
• New Hampshire Invasive Plant Species Watch List
• WeedUS - Database of Plants Invading Natural Areas in the United States