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A close-up of butterfly bush flowers.


Butterfly bush shrub

Spanish broom
Spartium junceum

Other common names: weaver's broom
Plant family: Pea family (Fabaceae)
Legal Status: Class A Noxious Weed
Year listed: 1998
Native to: Mediterranean regions in northern Africa, west Asia, and Europe

How would I identify it?
Overall: Spanish broom is a perennial, evergreen shrub with round, green stems that are leafless for much of the year and bright yellow, irregularly shaped flowers. Shrubs can reach a height between 6-10 feet.

Leaves:

  • alternate ; lance-shaped
  • less than 1 inch long
  • smooth on top but with long hairs on the leaf underside
  • only appear between February and early June

Flowers:

  • irregular shape , typical of flowers in the Pea family
  • bright yellow
  • about one inch long
  • fragrant
  • flowers grow in clusters at the end of stalks
  • bloom time is typically between July and early frost

Stems:

  • bright green
  • round

Line drawings are taken from 1,000 Weeds of North America, copyright of XID Service, Inc and used with permission. Permission granted by the author.

Where does it grow?

Spanish broom's high tolerance to drought and ability to produce nitrogen allow this shrub to grow in sunny, dry, areas with poor, often rocky soil. Like Scotch broom, it is typically found in disturbed areas including eroded slopes, vacant lots, and roadsides.

How does it reproduce?

Spanish broom reproduces primarily by seed.
  • One plant can potentially produce between 7,000 - 10,000 in just one growing season, and these seeds can be dispersed following soil erosion and heavy rainfall, or by hikers and roadside maintenance crews. 
  • Seeds can can remain dormant for at least five years, although broom seeds have been shown to survive for over 25 years.

Where does it occur in Washington?
Spanish broom is currently limited to small populations or individual shrubs in King, Kitsap, and Thurston counties. It appears to have been eradicated from San Juan County.

Why is it listed as a Noxious Weed?
Spanish broom is a close relative to Scotch broom, which you can see covering steep slopes and abandoned lots along roads and highways in much of western Washington.
  • Like Scotch broom, Spanish broom can dominate disturbed areas, where it can outcompete native plants and alter the soil nutrients.
  • It does not provide good forage for wildlife, and mature stands are noted to be a fire hazard in California.
  • It is currently listed as a Class B Noxious Weed in Oregon.

Because its distribution is still limited, Spanish broom is listed as a Class A Noxious Weed, which means that eradication of this plant is required everywhere in Washington.

How do I control it?
Overall: Because Spanish broom produces so many seeds, it is important to watch for new seedlings removal of adult plants, especially if the soil is disturbed. Fortunately, seeds do not appear to germinate when covered with 10 cm of soil, so heavy mulching may be an effective means to prevent new infestations. Revegetating the infested area with native plants or non-invasive garden ornamentals can help prevent reestablishment of the invasive plant.

Herbicide: Herbicide application following stem-cutting can be an effective combination. Please refer to the PNW Weed Management Handbook, or contact your county noxious weed coordinator.

Mechanical methods: Small plants and seedlings can be effectively controlled through hand hoeing. Hand-pulling can be effective when shrubs are still small and the entire root structure can be removed. Otherwise, the root fragments will resprout new plants. The best time to hand-pull is between July and September, especially when the soil is dry.  The stems of large shrubs can be cut; however resprouting will occur unless the cut stump is treated with herbicide. 

Biocontrol: There are currently no approved biocontrol insects for Spanish broom at this time.

For more information

You can download our Written Findings here.

 Last updated March 31, 2007