HPIPM:Perennial sowthistle

Taxonomy

Domain	Eukarya
Kingdom	Plantae
Phylum	Magnoliophyta
Class	Magnoliopsida
Superorder	Asteranae
Order	Asterales
Family	Asteraceae
Subfamily	Cichorioideae
Tribe	Cichorieae
Genus	Sonchus

Scientific Name

Sonchus arvensis

Common Name

perennial sowthistle

Perennial sowthistle (Sonchus arvensis)

Author: Tim Prather, University of Idaho, Department of Plant, Soil, and Environmental Sciences

Adapted from: Idaho Weed Resource webpage on perennial sowthistle.

Identification and Life Cycle

Perennial sowthistle (Sonchus arvensis) is an introduced perennial weed in the sunflower family (Asteraceae). Perennial sowthistle is an erect plant, branching in the upper portion, and capable of growing to 6 feet tall. Cotyledons are obovate, 0.3 inches long. Rosette leaves are crowded, spatula-shaped to deeply lobed, like a dandelion, and can be 10 inches long. Stem leaves are much reduced, usually not lobed, and scarce; all leaves are prickly toothed along the margins. Stems are hollow, sparsely branched. Both leaves and stems exude a milky latex when broken. Yellow, dandelion-like flower heads to 2 inches wide are borne from June until frost. The flower heads and their stems bear coarse, gland-tipped hairs. Seeds are reddish brown, 1/8 inch long, flattened, ribbed, and tipped with white plumes. The plant has extensive horizontal roots.

Habitats

Perennial sowthistle grows in cultivated fields, meadows, pastures, lakeshores, gardens, lawns, roadsides, and waste areas. It prefers moist rather than dry conditions.

Impacts

Perennial sowthistle is considered a noxious weed in many states. Perennial sowthistle can reduce crop yields, increase cultivation and herbicide costs, and lead to land depreciation.

Biology and Ecology

In general perennial sowthistle requires high light intensities to stimulate germination. In shade, perennial sowthistle will produce fewer, but larger, leaves to compensate for reduced sunlight. Perennial sowthistle takes 10 days from flowering to seed maturity. In 3 to 5 years, 80 percent of the initial seed in the soil will have germinated. Seeds are primarily disseminated by wind. Secondary dispersal occurs when seeds adhere to animals and farm equipment. Root stocks of perennial sowthistle can penetrate to a depth of 2 feet.

Management Approaches

Cultural, mechanical and chemical methods can be used to control perennial sowthistle.

Biological Control

There are currently no biological controls available for perennial sowthistle.

Mechanical and Cultural Control

Sheep or cattle grazing can suppress perennial sowthistle. Grazing should occur when plants are bolting. Cultivation in spring, when plants are in the rosette stage with 7-9 leaves or tilling roots into small segments in late spring and early summer will help reduce spread if conditions are not optimal for re-growth. Fallowing an infested field for year beginning in fall and cultivating every 3 weeks in spring can also reduce perennial sowthistle.

Chemical Control

Several chemical control options are available. For herbicide recommendations for specific grain rotations and weeds in Montana, please see the MSU Herbicide Chooser Tool.

Consult herbicide labels for additional rate, application, and safety information. Additional herbicide information can be found at http://www.greenbook.net.

Due to constantly changing labels, laws and regulations, the sponsors of this web site assume no liability for the suggested use of any chemicals noted in the management section. Contact your local pest management personnel for current information on labeled pesticides that can be used for the intended plant disease, insect pest or weed.

References

For more information and images please visit IPM Bugwood. http://www.ipmimages.org/search/action.cfm?q=perennial%20sowthistle