Scotch Broom (Cytisus scoparius)

Gallery:

Scotch broom field infestation

Scotch broom flowers

Scotch broom seed pods

Scotch broom growth habit

Scotch broom infestation following a timber harvest.

Common names:

Scotch broom, Scot’s broom, English broom

Scientific Name:

Cytisus scoparius (syns. Sarothamnus scoparius, Spartium scoparium)

Description:

Scotch broom is a fast growing shrub in the Fabaceae (pea) family, characterized by its masses of yellow flowers. It grows upright on young green, 5-angled stems which are hairy. Broom forms dense stands and are shade intolerant. Mature plants can reach 10 feet in height although most plants are typically 3-5 feet tall. Scotch broom is deciduous nitrogen fixing plant. Scotch broom is an invasive plant found in low elevations from British Columbia to California.

Life cycle:

Annual, Biennial, Perennial

Height of mature plants

4 to 8 feet

Flower color:

Yellow

Bloom time:

April to June

Look-a-likes:

It can be confused with the less common Spanish broom, Spanish broom has fewer round stems, very few leaves, and larger yellow flowers.

Habitat:

The areas most infested by Scotch broom are disturbed (logged or burned) sites, grasslands, open forests, and riparian corridors. The plant likes coastal areas and low elevations in dry conditions with plenty of sunshine. Scotch broom flourishes in infertile soil because it is a nitrogen fixing plant which allows it to grow where many plants cannot. Scotch broom likes sandy, acidic and dry soil.

Impacts:

Scotch broom is a pioneer species known to displace native plants and smother tree transplants increasing tree death or slowing growth in the early years. It readily invades disturbed sites, natural areas, dunes, and forestlands. Broom control costs on right-of-ways, public facilities, parkland and private property are in the millions of dollars each year due to its rapid growth and persistent nature. Scotch broom is a prolific seed producer of long-lived (10 years plus) seeds. Broom stands establish persistent soil-seed banks requiring long-term commitment to exhaust. The costs attributed to Scotch broom come from labor and chemical inputs needed to control infestations ($47 million annually) in timberlands and from lost productivity. Pollen production during bloom time also can be quite an allergen source for allergy sufferers.