The issue: Tumble mustard

Tumble mustard (Sisymbrium altissimum) is an annual invasive plant from Europe that grows 2-5 feet tall. It is typically a winter annual, but will also behave like a summer annual or even a biennial. The mature plant dries and breaks off at the ground, spreading seeds as it blows in the wind. It will tolerate broad growing conditions and easily establishes in disturbed sites.

After germination, tumble mustard forms a low-growing rosette until it gets the signal to produce flowers. The rosette leaves are up to six inches long with deep lobes or pinnate leaflets. The upper leaves have narrow, linear lobes. The yellow, four-petaled flowers give rise to a silique seed head that is held mostly upright, 2-4 inches long. A silique is a long pod that is divided in two by an internal membrane.

Tumble mustard reproduces only by seed. Seeds may remain viable up to ten years in field conditions. Control efforts must focus on eliminating seed production and spread.

Integrated pest management options:

· Prevention: Feed weed-free hay; keep ditch banks free of seed-producing weeds; clean vehicles and equipment.

· Mechanical: Hand dig or cultivate rosettes or bolting plants before seed production; flame weed young seedlings in the fall.

· Cultural: Provide growing conditions for healthy competition from desirable plants; soil solarization; organic mulch at least 3 inches deep.

· Biological: Livestock will graze on young plants.

· Chemical: Pre-emergent herbicides applied in the fall; post-emergent broadleaf herbicides with 2,4-D in late fall or early spring—don’t apply when temperatures will be above 85 F for three days. Be sure the target weed and crop, or landscape situations are listed on the product label. Always read and follow herbicide label directions.

Combine them:

These control options are all more effective when combined with the other efforts described.

For more information, contact Ron Patterson, University of Idaho Extension horticulture/agriculture educator in Bonneville County, at 208-529-1390 or rpatterson@uidaho.edu.