How To Remove Scotch Broom

How to Manage Pests

Pests in Gardens and Landscapes

Brooms

Published 6/twenty

In this Guideline:

French broom invading a hillside near Bodega bay, California.

French broom invading a hillside almost Bodega bay, California.

Spanish broom.

Bridal veil broom.

Scotch broom gall mite.

Brooms are a group of shrubs that were introduced into North America from Europe and North Africa in the mid-1800s. Brooms tin can exist found growing along roadsides, forestlands, coastlines, riparian areas, brushlands, and disturbed areas. Initially introduced as ornamentals, they were later promoted by federal and state agencies for erosion control forth roadsides and in mined areas. As a result, five broom species have go naturalized in California and are classified every bit invasive weeds by many federal, state, and local jurisdictions.

These highly competitive shrubs grow rapidly and form dense stands that both people and wild animals find impenetrable. Their dense stems make regeneration of nigh other plant species hard or impossible, and they create a unsafe burn hazard. In improver, as legumes, brooms can set atmospheric nitrogen, increasing soil fertility and giving a competitive advantage to other non-native weeds that, unlike the local natives, thrive on loftier nitrogen levels.

The four most common broom species in California are Scotch broom (Cytisus scoparius), French broom (Genista monspessulana), Spanish broom (Spartium junceum), and Portuguese broom (Cytisus striatus).

Although many retailers accept stopped selling the species mentioned above, some nurseries withal sell these and other brooms, including many hybrids. Residents should avoid planting them every bit many of these accept like invasive characteristics. Some of the available species include sugariness broom (Cytisus x spachianus and Genista racemosa) and multiple Scotch broom hybrids including Burkwood's broom (Cytisus 10 burkwoodii), Lilac Time, Moonlight, and Lena to name a few.

The safest approach is to avert planting any broom species. Several alternate establish species have similar attributes merely are not invasive. Contact your county UC Master Gardener office or visit PlantRight.org for a list of recommendations (See Resources).

IDENTIFICATION AND Biological science

Brooms are upright shrubs that grow three to 10 anxiety tall. They generally produce bright xanthous, pea-shaped flowers from April to June.

Scotch and Portuguese brooms produce their flowers in the leaf axils, while French and Spanish brooms have flowers at the co-operative tips. The flowers of French broom are substantially smaller than those of the other 3 mutual species. In some areas, Scotch broom flowers can be multicolored, with red or imperial spots or petals. Bridal veil broom (Retama monosperma) is a white-flowered broom that has become invasive in parts of Southern California.

Stem shape can be used to distinguish betwixt broom species. Scotch broom has a 5-angled stem (star-shaped when viewed in cantankerous-section), French and Portuguese take an 8- to ten-angled stem, and Spanish broom has a finely ribbed stem, making information technology most round.

Foliage characteristics also identify the species. Castilian broom produces unproblematic leaves, while the other three species have by and large trifoliate leaves. For most species, new leaves produced in spring are frequently lost during hot, dry summer months or periods of stress, giving the plants their characteristic whisk-broom appearance. Scotch, Portuguese, and Spanish brooms are deciduous while French broom is an evergreen. Tabular array 1 shows identifying features of these four broom species.

All four broom species produce dark colored pods in mid- to belatedly summertime that contain shiny greenish-brown seeds. Invasion and spread of brooms are entirely driven by seed dispersal.

The pods ripen during the dry out summertime months, then explosively eject their seeds several feet away, making a popping noise aural for some distance. All brooms are prolific seed producers, with a single shrub producing every bit many equally 2,000 to 3,500 pods containing up to 20,000 seeds.

Betwixt 30% and 60% of seeds are expected to germinate the first year, with the rest staying fallow and germinating at lower rates in subsequent years. Germination rates vary beyond species, sites, and years. Under most conditions, the majority of new seedlings die, but withal, the large number of seeds produced by a single plant tin can outcome in many seedlings. The seeds accept an impervious seed glaze, enabling some seeds to remain dormant in the soil for decades and making long-term direction difficult.

Afterwards germination, growth of seedlings for the first ii years tin be slow, such that people sometimes practice not recognize that they have a broom problem until it is several years along. At that signal, or sometimes before, growth becomes very rapid—with plants growing as much every bit three or 4 feet in one year. Rapid growth continues for another 3 to 4 years, followed by half dozen to 8 years of relatively slow growth. Adjacent is a period of senescence, with more dead woody tissue than green. Plants typically live 12 to 17 years just tin can survive for equally long as a quarter-century.

In established broom stands, seeds often remain dormant until older plants are removed or soil disturbance occurs, at which point a carpet of seedlings will announced. Brooms don't ordinarily reach flowering maturity until the 2nd or third year of growth, which allows for targeted removal of established shrubs get-go, followed by seedlings and younger plants thereafter.

Distinguishing Features of 4 Common Broom Species in California.
Scotch broom (Cytisus scoparius)	French broom (Genista monspessulana)	Spanish broom (Spartium junceum)	Portuguese broom (Cytisus striatus)
Stems: 5-sided; star-shaped cross section Leaves: compound, three leaflets, deciduous, sometimes single on new twigs	Stems: eight to 10 ridges; almost circular cross section. Leaves: compound, 3 leaflets, evergreen, normally dense	Stems: smooth or finely ribbed; round cross section Leaves: simple, deciduous, thin	Stems: 8 to x ridges; nearly round cantankerous section Leaves: chemical compound, three leaflets, deciduous, sometimes single on new twigs
Flowers: unmarried or paired in leaf axils Petals: yellowish or partially red	Flowers: four to ten in clusters at stop of short branches Petals: yellowish	Flowers: several in open up racemes at branch tips Petals: yellow	Flowers: single or paired in foliage axils Petals: yellow
Seed pods: flattened, but margins hairy	Seed pods: slightly flattened, entirely covered with long hairs	Seed pods: slightly flattened with few, if any, long hairs	Seed pods: slightly inflated, entirely covered with long hairs

MANAGEMENT

The two primary methods for managing brooms are mechanical removal and treatment with herbicides (weed killers). Broom establishment is through seed dispersal, so maintaining a salubrious embrace of desirable vegetation and reducing soil disturbance may reduce the potential for broom invasion. Ongoing monitoring for new seedlings is crucial for successful management.

Mechanical Control

Small infestations can exist removed by hand-pulling or mechanical grubbing. A multifariousness of tools tin can aid in removal, including shovels or picks, chains, or specialized tools such as the Brush Grubber or The Uprooter. Information technology is easiest to remove plants in early spring or tardily fall when the soil is moist and roots can be dislodged. Grubbing when the soil is dry and difficult usually will pause off the stems, leaving rootstalks that may resprout. Fortunately, with brooms, fragments of stems do not survive to produce new roots every bit in some weedy species.

Mowing broom plants gives poor command unless performed repeatedly throughout the growing season. Within a couple months of formation, young plants usually take produced hugger-mugger rootstocks large plenty to recover from a single mowing. Use extreme circumspection when mowing during spring and summertime considering of the potential for wildfires. Mowing later in the season also tin spread seeds.

Lopping mature plants most the base will provide some control if washed when plants are moisture-stressed in late summer, or in late spring following a winter with little rainfall. Lopping at other times can atomic number 82 to vigorous resprouting.

Under most conditions in California, brush rakes and bulldozers that go out pieces of rootstocks behind practise not provide successful command. In some cases, brush removal in late summer, when plants experience moisture stress, can slow their ability to recover. Still, using large equipment to clear land may as well promote seedling establishment, making follow-up control essential.

Cultural Control

Burning solitary is mostly not an effective method for controlling brooms. Although burning can remove large amounts of debris, it can also increase the broom population, as information technology removes competitive vegetation and releases nutrients into the soil. A very hot fire volition kill seeds, just a cooler burn will stimulate the germination of broom seeds left in the soil.

Cutting the aboveground vegetation of broom and allowing information technology to dry out on site, followed by called-for, can effectively command resprouting. Burning is more than effective when followed by an herbicide awarding or subsequent burnings, and then by revegetation with desirable species. It is important to utilize a control strategy following a burn down, otherwise the broom population in subsequent years may become worse than before.

Grazing can provide control in small areas, if the grazing pressure is loftier enough to continually suppress growth. Goats and sheep have been shown to feed on resprouting shrubs, including brooms. In horses, however, ingestion of Scotch broom is reported to crusade neurologic furnishings such as excitement and loss of muscle control and remainder, likewise as digestive and reproductive effects.

Biological Control

In the 1960s, 3 insects were introduced equally 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 ii species are specific to Scotch broom, while the seed protrude also attacks Portuguese broom, Spanish broom, and French broom. Although all three insects are established, none provide significant command.

Recently, a new agent chosen the Scotch broom gall mite (Aceria genistae) was plant in California. Although this small arthropod was non officially released as a biocontrol amanuensis, information technology has spread across much of Northern California and the Pacific Northwest. Observationally, the mite appears to reduce Scotch broom seed production and at high densities can cause extensive stalk dieback and establish bloodshed. Because brooms are serious problems in many countries, the International Broom Initiative is evaluating other insects and pathogens in their native countries to make up one's mind their control potential.

Chemical Command

California residents can apply postemergence herbicides containing the active ingredients triclopyr and glyphosate for decision-making brooms. These herbicides can exist used either alone or as a combination of glyphosate with triclopyr or imazapyr.

In areas near rivers or streams, it is important to use the proper conception of these herbicides. Ester formulations of triclopyr or imazapyr, for example, are non registered for use near water, and almost glyphosate formulations cannot be used near water. Depending on the compound, these herbicides can be applied equally foliar sprays, cutting-stump treatments, or basal bark applications.

When using herbicides, exist sure to prevent them from getting on desirable plants. Because glyphosate is a nonselective compound, it volition harm or impale other vegetation. Triclopyr is a broadleaf herbicide that will not injure grasses merely will damage or kill other broadleaf plants.

Home gardeners and professional applicators should always article of clothing appropriate protective equipment as stated on the herbicide label.

Foliar Sprays. Herbicides practical to the canopy of broom are often applied when the plants are actively growing from Apr to July. In balmy climates where young broom stems can stay green year-round, tardily fall and winter applications tin can as well exist effective.

Herbicides can be practical every bit foliar sprays using one of two methods. The first is "spray-to-wet," where all leaves and stems should glisten following an awarding. Coverage, nevertheless, should not exist to the point of runoff. Spray-to-wet applications are made using a haversack or manus sprayer with a flat fan or adjustable spray nozzle. The other foliar method is a low-book technique called a "drizzle" application, using a spray gun fitted with an orifice disk.

Rather than spraying the entire canopy as in a spray-to-wet treatment, a drizzle application is made to the canopy using an intermittent blueprint. It is important to note that the 2 foliar techniques apply the same amount of herbicide agile ingredient on a given plant but within different total volumes of water. In a spray-to-moisture application, total spray book tin can range from 20 to 100 gallons per acre, while the full volume using the drizzle technique will exist between 2 and 5 gallons per acre.

The drizzle application is useful for managing plants in areas that are hard to access. The drizzle nozzle will reach a target found fifteen to xx anxiety away, while a flat fan nozzle may only achieve plants ii to 3 anxiety away. Because of larger spray droplets, the drizzle method also minimizes herbicide drift. The lower volume of water used as well reduces sprayer refilling requirements and total weight, potentially reducing applicator fatigue.

For spray-to-wet applications, products containing at least 41% glyphosate as the active ingredient can provide proficient to excellent control of brooms when applied at 2.5 ounces of product per gallon of water (two% of the total solution). Some products available for utilise in the home landscape with this concentration of agile ingredient are Roundup Pro, FarmWorks Grass & Weed Killer 41% Glyphosate Concentrate, RM43 Full Vegetation Command, Compare-N-Save Grass & Weed Killer Concentrate, and Remuda Total Strength.

Glyphosate products that have a lower concentration of agile ingredient, such as Roundup Concentrate (18% active ingredient), volition require almost 6 ounces of production per gallon of h2o (iv.vii% of the total solution) for effective control.

Triclopyr is bachelor in either ester or amine formulations. Triclopyr ester is more effective on brooms, since this formulation is more easily absorbed into the foliage and stems. Products containing a minimum of 61% active ingredient of triclopyr ester can provide practiced to fantabulous control when applied at i to 1.25 ounces of product per gallon of h2o (0.75% to one.5% of the total solution). One such product with this concentration is Brushtox Brush Killer with Triclopyr. Other less full-bodied formulations, such as Crossbow, are also available.

Mixing triclopyr ester with commercially available seed oils tin offer better penetration. One available product is Hasten-EA modified vegetable oil concentrate. Mix this at 1.25 ounces of production per gallon of herbicide solution (1% of the total solution).

Amine formulations of triclopyr include Bayer BioAdvanced Brush Killer Plus, Ortho GroundClear Poison Ivy & Tough Castor Killer1, and Monterey Brush & Vine Control.

For drizzle applications (low volume, every bit per production labels), products containing at least 41% glyphosate can provide good to excellent control of brooms when applied at 13 ounces of product per gallon of h2o (ten% of the full solution).

Triclopyr ester tin also be applied using the drizzle method. Products containing 61% active ingredient should be applied using 13 ounces of product (ten% of the full solution) and 13 ounces of seed oil (10% of the full solution) per gallon of water.

Since drizzle applications use more than concentrated herbicide solutions, ane gallon of herbicide solution may fairly treat upward to one-half acre of densely populated broom.

When air temperatures are higher than eighty°F, it is improve to utilize glyphosate or the amine formulation of triclopyr, since triclopyr ester is subject to vaporization.

Cut-Stump Awarding. Cut-stump treatments can be done throughout the yr. Immediately after cut, utilise the herbicide to the cut surface with a paint castor, spray canteen, or plastic squeeze bottle. Delaying awarding volition outcome in poor control, because the cut surface will quickly dry, preventing movement of the chemic into the found.

For small stumps, completely embrace the cut surface. For big stumps, it is but necessary to wet the outer ring of woods next to and including the bark. For small-stemmed shrubs, cut the stems with loppers or clippers and paint or sponge the herbicide solution onto each cut end.

For triclopyr ester products containing 61% active ingredient, apply 1 part production and 4 parts water. For triclopyr products containing viii% amine, such as Ortho Poison Ivy Tough Castor Killer1 utilise undiluted.

Glyphosate tin too be used as a cut-stump awarding. If using a product containing xviii% glyphosate, make a 1:1 solution of the product and water or use undiluted. For products that contain 41% glyphosate, use one office product and 3 parts water.

Basal Bawl Application. Concentrated formulations of triclopyr ester tin can exist applied to the trunks of broom using a backpack sprayer, spray canteen or wick applicator. Thoroughly cover a 6-inch band around the basal trunk of the shrub. Basal bark applications can be made well-nigh any time of the year, fifty-fifty afterwards leaves have senesced. For triclopyr ester products with 61% agile ingredient, the application ratio is xiii ounces of product (ten% 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.

After implementing a control technique, it is important to monitor the area for regrowth. One application of an herbicide does not ever completely command brooms. Watch treated areas closely for at least a year and retreat equally necessary.

Warning ON THE USE OF CHEMICALS

Resources

UC Master Gardeners. (Accessed June viii, 2022).
The PlantRight Programme. plantright.org/ (Accessed June 8, 2022).

REFERENCES

Bossard C, Randall J, Hoshovsky MC. 2000. Invasive Plants of California'south Wildlands. Berkeley: Academy of California Press. (Accessed June 8, 2022).

DiTomaso JM, Healy EA. 2007. Weeds of California and Other Western States. UC ANR Publication 3488. Oakland, CA.

DiTomaso JM, Kyser GB, et al. 2022. Weed Control in Natural Areas in the Western Us. Davis: Academy of California Weed Research and Information Center. (Accessed June 8, 2022).

Hoshovsky MC. 1986. Element Stewardship Abstruse for Cytisus scoparius and Genista monspessulana (Scotch Broom, French Broom). Arlington: The Nature Conservancy. (Accessed June 8, 2022).

Hoshovsky MC. 1986. Element Stewardship Abstract for Spartium junceum (Spanish Broom). Arlington: The Nature Conservancy. (Accessed June eight, 2022).

Oneto SR, Kyser GB, DiTomaso JM. 2010. Efficacy of Mechanical and Herbicide Control Methods for Scotch Broom (Cytisus scoparius) and Cost Assay of Chemic Control Options. Journal of Invasive Constitute Scientific discipline and Management 3:421-428.

Parker IM. 2000. Invasion dynamics of Cytisus scoparius: A matrix model approach. Ecological Applications 10(3):726-743

Parker IM. 2001. Safe site and seed limitation in Cytisus scoparius: Invasibility, Disturbance, and the Role of Cryptogams in a Glacial Outwash Prairie. Biological Invasions 3(4): 323-332.

PUBLICATION Information

[UC Peer Reviewed]

Pest Notes: Brooms

UC ANR Publication 74147

AUTHORS: Scott R. Oneto, UC Cooperative Extension, Joseph Yard. DiTomaso, Establish Sciences, UC Davis, and Guy B. Kyser, Institute Sciences, UC Davis.

TECHNICAL EDITOR: K Windbiel-Rojas

ANR ASSOCIATE EDITOR: AM Sutherland

EDITOR : B Messenger-Sikes

Produced by University of California Statewide IPM Program

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