Donaldson, S. and Hanson Mazet, W. 2010, A Northern Nevada Homeowner's Guide to Identifying and Managing Prickly Lettuce, Extension, University of Nevada, Reno, FS-10-28

Black medic growth

Typical plant growing in disturbed site. Photo by S. Donaldson.

Black medic leaves

This photo shows two compound leaves, each made of three leaflets.

Note the tooth at the tip of each leaflet. Photo by W. Hanson Mazet.

Black madic flowers

The tiny individual yellow flowers are arranged in clusters to form

the flower heads. Photo by S. Donaldson.

Black medic seedlings

Seedlings leaves are pale on the underside. Photo courtesy of J. DiTomaso, UCCE.
 

 

Other common names

China lettuce, wild lettuce, compass plant

Scientific name

Lactuca serriola

Family

Asteraceae

Description

A bushy, much‐branched drought‐tolerant plant that grows to 5+ feet tall. A common weed of mid‐summer in disturbed areas, prickly lettuce forms a rosette (ground‐hugging form) in winter or early spring and grows flowering stems in summer. All plant parts ooze a milky, sticky sap when broken.

  • Leaves

    Larger below and smaller above; twist at the stem to point upright. They have sharp spines on the underside of the midrib and on the edges, and clasp the stem. Some plants have lobed leaves, and other do not.

  • Stems

    Prickly stems grow from the base of the plant and branch above

  • Flowers

    Small and yellow with toothed tips on the petals. Blooms from summer to fall.

  • Seeds

    Produces a puffball of wind‐dispersed seeds.

  • Roots

    Grows a deep taproot.

Native to

Europe; naturalized throughout the United States

Where it grows

Gardens, yards, vacant lots, roadsides, urban areas and other disturbed or unmanaged sites

Life cycle

Winter annual (sprouts in fall or early winter) or sometimes biennial (flowers and dies in the second year)

Reproduction

Reproduces by seed.

Control methods

Preventing seed production is key to controlling this weed. Each prickly lettuce plant can make as many as 2,300 seeds. A single plant can result in a large infestation the following year.  The seeds are ready to sprout soon after they disperse. Plants are most easily removed when they are small rosettes.

 

  • Mechanical

    Dig, hoe or pull young plants. Use mechanical control methods prior to formation of flowers and seeds.  Mowing is not effective, as plants will regrow and flower.

    Cultural

    Plant desirable vegetation to compete with prickly lettuce; minimize soil disturbance.  

    Biological

    Sheep and goats will graze plants.

    Chemical

    Apply broadleaf‐selective herbicides or glyphosate on young plants. Glyphosate is nonselective and will damage desirable plants. Herbicides are not very effective once flowering stems have appeared. Herbicide resistance has been reported.

References

Printable    Version    (PDF)

Learn more about the author(s)

Wendy Hanson Mazet
Wendy Hanson Mazet
 

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