Scotch Broom (Cytisus scoparius(L.) Also known as common broom, European broom, Irish broom and English broom.
Broom is a native to Europe and was introduced into the United States in 1800s as an ornamental and as a plant for stabilizing road cuts. Broom was being sold as an ornamental in California in the 1860s and by 1900 had become naturalized on Vancouver Island, where it was introduced by Captain Walter Grant in 1850. Broom invades roadsides, disturbed areas, pastures and native grasslands. Broom is widespread in the Pacific Northwest. Broom is an upright, taprooted evergreen shrub in the legume family growing from 1 to 6 feet in height with woody stems. The flowers are pea-like and bright yellow. Scotch broom reproduces vegetatively or by seed.  It has been purposefully propagated from cuttings and it sprouts back after cutting. Scotch broom is a prolific and tenacious species: a single bush can produce up to 60 seed pods, with each pod containing five to eight seeds. Broom pods often open explosively, especially in a drying wind, and the seeds may be widely scattered. The seeds are flat brown to black in color and have hard coats enabling them to survive in the environment for up to 80 years. The seeds are transported from place to place in mud stuck to vehicles, equipment, and the feet of animals. Seeds may be carried via runoff from roads into streams and gullies. Broom forms dense brush over six feet tall. The brush fields diminish habitat for grazing animals and shade out native grassland plants in invaded areas, therefore favoring the invasion by other woody, non-grassland plant species. Oregon estimates that broom is responsible for $47 million in lost timber production each year.

Scotch Broom Stand

Control

Physical: These include hand weeding, by pulling, digging, or hoeing; or cutting the above-ground portion (about half the roots will resprout, but if cutting is done before seeds are set, spreading will be contained). Chopping or mowing mechanically has been used in some locations, where there is no concern about removing all vegetation. Continual mowing is likely to produce entire pastures of broom because of resprouting from the roots.

Mechanical: Chopping, Cutting or Mowing:  Scotch broom may be trimmed back by tractor-mounted mowers on even ground or by scythes on rough or stony ground.  However, these methods are non-selective weed control techniques and will cut all plant species which may not need control.  Broom plants usually require several cuttings before the underground parts exhaust their reserve food supply.  If only a single cutting can be made, the best time is when the plants begin to    flower.  At this stage the reserve food supply in the roots has been nearly exhausted, and new seeds have not yet been produced.  After cutting or chopping with mechanical equipment, broom may resprout from root crowns in greater density if not treated with herbicides

Fire: Flame throwers or other weed burners can be used to girdle the lower stems. Prescribed burns in grass consume some broom seeds and break the seed coats of others, allowing pathogens to enter and kill the seeds. Still other seeds may be stimulated to germinate so that plants can be pulled out. Neither method is likely to be effective without combination with other methods, such as spraying with herbicides.

Biological control

Competition:  Sowing native plant species which have the potential to out-compete weedy exotics for important resources is usually a preventive method of weed control.  In some cases later successional plants may be encouraged to take root among the unwanted vegetation. Several species of insects known to control Scotch broom in its native habitats have been introduced in California; none of these have shown long-term effectiveness, but several species remain to be tried and this may eventually prove to be a good method of control. A twig mining moth, a seed weevil, and a shoot tip moth are available for control of broom. The twig mining moth and seed weevil have become established within Idaho, Oregon and Washington and have shown slight to moderate control in some areas. Research on the insect fauna on Scotch broom in England has shown that there are 9 Lepidoptera, 5 Diptera, 1 Hymenoptera, 7 Coleoptera and 13 Hemiptera which regularly feed on broom.  At present only 10 of these European broom insects are found in North America and only 5 are present in California.  Given such a diverse insect fauna, there is still potential for introducing other species to help control broom. Livestock grazing as a control measure may be effective, although broom is slightly toxic and unpalatable to some livestock.  The continued removal of the tops of seedlings and resprouts by grazing animals prevents plant development and seed formation and gradually weakens the underground parts. Grazing must be continued until the seed bank is eliminated, as the suppressed plants return quickly after livestock is removed. Sheep and goats have been effective for grazing broom. Thus sheep and goat grazing may be a practical alternative to mowing. Sheep are valuable not only for weed control but also for additional income from the sale of their wool and their contribution of fertilizer to the soil.

Chemical control 

Most herbicides so applied are non-selective and will kill most, if not all, of the vegetation sprayed.  Those species that survive the treatment may, after repeated sprayings, form an herbicide-resistant vegetation cover, thus creating a more difficult problem to deal with. Broadcast herbicide application may be most effective where the weed infestation is very dense and needs to be killed and dessicated prior to burning.  It may also be useful following the removal of mature plants so as to reduce the soil seed bank. Various broadcast herbicides, including 2,4-D, picloram, glyphosate and triclopyr have been effective, but must be used in controlled circumstances, with careful attention being paid to desirable vegetation that may also be affected.
    In general, when using the broadcast application method, plants should be sprayed only in full leaf.  Results are poor if plants are sprayed when the leaves are developing and when plants are in full flower before leaf development.  The best results have been obtained when plants are in the seed head stage in late summer and early autumn.

Spot Chemical Methods:  Spot chemical methods consist of various techniques for manually applying herbicides to individual plants or small clumps of plants (such as stump resprouts).  Spot herbicides, applied to either stems or cut stumps, are labor intensive but have proven effective. They are most efficient when the density of stems to be treated is low.

    1) Stem injection:  Herbicides are injected into wounds or cuts in the stems or trunks of plants to be killed.  The herbicide must penetrate to the cambial tissue and be water-soluble to be effective.  The chemical is then translocated throughout the tree and can provide good root-kill, which is important in order to prevent resprouting.

    2) Cut stump treatment:  Herbicides are directly applied to the cambial area around the edges of freshly cut stumps.  Application must occur within 5-20 minutes of cutting to ensure effectiveness. 

    3) Basal/Stem sprays:  This technique involves the use of backpack sprayers in applying high concentrations of herbicides in oil or other penetrating carriers to the basal portion of stems to be killed.  The oil carrier is necessary for the mixture to penetrate bark and enter the vascular system.  This method gives good root kill, especially in the fall when vascular fluids are moving toward the roots.  This method may be easier to use with small diameter stems than the two previous techniques.

Refer to the label for all herbicides
Always follow label directions prior to use

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Questions: contact Steve Van Vleet or phone (509) 397 - 6290