How Can I Control Broom Weed In My Landscape?

Do you have a small infestation of broom weeds?

Do you wish to try controlling brooms with chemical control?

Do you wish to control brooms with foliar sprays?

Do you wish to control brooms with cut-stump applications?

Do you wish to try controlling brooms by burning them?

Mechanical control is recommended for small infestations. Brooms can be removed by hand-pulling or mechanical grubbing. A variety of tools can aid in removal, including shovels or picks, chains, or specialized tools such as the Brush Grubber or The Uprooter. It is easiest to remove plants in early spring or late fall when the soil is moist and roots can be dislodged. Mowing broom plants gives poor control unless performed repeatedly throughout the growing season. Lopping mature plants near the base will provide some control if done when plants are moisture-stressed in late summer, or late spring following a winter with little rainfall.

Foliar sprays should be applied when the brooms are actively growing from April to July. In mild climates late fall and winter applications can also be effective. Glyphosate products that have a lower concentration of an active ingredient, such as Roundup Concentrate (18% active ingredient), will require about 6 ounces of product per gallon of water for effective control. Triclopyr is available in either ester or amine formulations. Triclopyr ester is more effective on brooms. Products containing a minimum of 61% active ingredient of triclopyr ester can provide good control when applied at 1 to 1.25 ounces of product per gallon of water.

Cut-stump treatments can be done throughout the year. Immediately after cutting, apply the herbicide to the cut surface with a paintbrush, spray bottle, or plastic squeeze bottle. For small stumps, completely cover the cut surface. For large stumps, it is only necessary to wet the outer ring of wood next to and including the bark. For triclopyr ester products containing 61% active ingredient, use 1 part product and 4 parts water. If using a product containing 18% glyphosate, make a 1:1 solution of the product and water or use undiluted. For products that contain 41% glyphosate, use 1 part product and 3 parts water.

Concentrated formulations of triclopyr ester can be applied to the trunks of the broom using a backpack sprayer, spray bottle, or wick applicator. Thoroughly cover a 6-inch band around the basal trunk of the shrub. Basal bark applications can be made almost any time of the year, even after leaves have been senesced. For triclopyr ester products with 61% active ingredient, the application ratio is 13 ounces of product (10% of the total solution) and 25 ounces of seed oil (20% of the total solution) per gallon of water. Glyphosate and the amine formulation of triclopyr provide poor control using this technique.

Burning alone is not an effective method for controlling brooms. Although burning can remove large amounts of debris, it also removes competitive vegetation of the brooms and releases nutrients into the soil. A hot burn will kill seeds, but a cooler burn will stimulate the germination of broom seeds left in the soil. Cutting the aboveground vegetation of broom and allowing it to dry on-site, followed by burning, can effectively control resprouting. Burning is more effective when followed by an herbicide application or subsequent burnings, and then by revegetation with desirable species. It is important to employ a control strategy following a burn.

In the 1960s, three insects were introduced as biological control agents on brooms—the Scotch broom seed beetle (Bruchidius villosus), the Scotch broom seed weevil (Exapion fuscirostre), and the Scotch broom twig miner moth (Leucoptera spartifoliella). The latter two species are specific to Scotch broom, while the seed beetle also attacks Portuguese broom, Spanish broom, and French broom. Although all three insects are established, none provide significant control. Recently, a new agent called the Scotch broom gall mite (Aceria genistae) was found in California. Observationally, the mite appears to reduce Scotch broom seed production and at high densities can cause extensive stem dieback and plant mortality.