Scotch Broom
By Eva Varga, Coos SWCD EQIP Outreach Coordinator
A shrub, between 2 to 6 feet in height, Scotch Broom has compound leaves, with three thin clover-like leaflets. Its flowers are yellow-red in color and irregular-shaped with five petals. Its pods are like those of p ea pods, but long, thin and hairy. The pods explode on hot days when the seeds are ripe to aid distribution of seeds. The branches are stiff and angled in cross-section. Both the leaves and pods are poisonous.
Often sold in nurseries, planted as an orna mental, and used in floral arrangements, Scotch broom easily escapes cultivation. It rapidly invades disturbed areas, suppressing or displacing native plant species including commercially important conifer seedlings. It has several characteristics that promote its invasiveness:
- Capability of forming dense, one-species stands and thickets;
- Rapid vertical growth and intense spatial competition;
- Tolerant to drought and cold;
- Profuse seed production (a mature plant of 3-8 years can produce 2,000 to 3,500 pods, encasing up to nine seeds per pod);
- Longevity of seed banks (seeds have an impervious coat enabling them to remain viable in the soil for long periods, up to 30 years)
- Deep roots;
- Ability to resprout from stumps;
- Long life span (usually from 10 t o 15 years although individual plants can live for over 20 years);
- Adaptability to various ecological niches; and
- Lack of natural enemies.
Management techniques
Several techniques have been used to control Scotch broom in urban areas or forest plantations. Unfortunately, most current control techniques are not particularly effective.
Manual cutting or pulling:
Manual or hand pulling can be effective if care is taken to extract the entire stump and roots, minimize soil disturbance, and not spread seed. T his technique is very labor intensive and costly. Unfortunately, the treatment needs to be repeated over a number of years because of broom\rquote s ability to resprout. Frequently, hand pulling disturbs the surrounding soil and creates ideal conditions for additional broom seeding.
Mechanical cutting or pulling:
Brush rakes, straight blading, and hydroaxes with tracked vehicles have been used to uproot, pile or crush broom thickets. Mechanical cutting with bulldozers or other heavy equipment is very costly. While effective in removing large stems in preparation for conifer planting, the large amount of disturbed soil creates an ideal situation for broom resprouting. In addition, broom seeds may stick to equipment and be distributed further either throughout the s ite or to other areas in which the equipment may work in the future.
Burning
Burning broom-infested sites has been used to remove flowering stalks. However, broom seeds germinate readily in the soil after light to moderately severe burns and broom colonies quickly re-establish. In addition, burning may be undesirable in certain areas due to smoke pollution.
Biological control
Using sheep and goats to control broom has been attempted in Canada, the United States and New Zealand with mixed results. Biocontrol strategies using parasitic insects and mites have been attempted in some areas. For the most part, while broom populations may be reduced, enough seed matures and escapes to enable the broom to spread. Under experimental conditions, three fungal pathogens, Fusarium tumidum, Pleiochaeta setosa, and Chrondrostereum purpureum have been investigated in British Columbia. However, more research is required and a commercial bio-herbicide agent is not yet available.
