Scotch broom

Cytisus scoparius

   

Family: Fabaceae

Other common names: broomtops, common broom, European broom, Irish broom, Scottish broom

Weed Class: B

Year Listed: 1988

Native to: Europe

Toxic: livestock

Other Legal Listings: WA Quarantine list, WAC 16-750

additional photos

 

   

Why is it a noxious weed?

It displaces native and beneficial plants, causing loss of grassland and open forest. It aggressively spreads to form monocultures, replacing desirable forage grasses and young trees. Seeds are toxic to livestock and horses.

How would I identify it?

General Description: Scotch broom is a perennial, many-branched, shrub ranging in height from 3 to 10 feet tall.

Flower Description: Flowers are typical of those in the pea family. They are bright yellow, about 3/4 inches long and have 5 petals.

Leaf Description: There are few leaves. The upper are simple and the lower are 3 parted. They are deciduous and pointed at both ends. Leaves may fall early in the year, leaving bare green stems.

Stem Description: Stems are woody and dark green. Young branches have 5 green ridges with hairs. When mature, stems become glabrous and ridges disappear. Young stems remain green throughout the year.

Fruit/Seed Description: Seed pods are brown-black, legume-like, flattened and have hairy margins with several seeds per pod.

May be confused with: Spanish broom (Spartium junceum) and French broom (Genista monspessulana), Class A noxious weeds in Washington, and gorse (Ulex europaeus), a Class B noxious weed in Washington, look similar to Scotch broom. Spanish broom has round stems and flowers only at stem tips. French brooms's leaves are all three-parted and flowers are in clusters of 4-10. Gorse has spines on its stems. If you need help with plant identification, please contact your county noxious weed coordinator.

How does it reproduce?

Scotch broom reproduces by seed. Each seed can remain viable for over 30 years (some estimates are as long as 80 years).
 

Where does it grow?

Scotch broom can be found on roadsides, pastures, grasslands, open areas and areas of recent soil disturbance. Please click here to see a distribution map of Scotch broom in Washington.
 

How do I control it?

General Control Strategy

Because plants can produce thousands of seed each year and these seeds can survive for a long period of time in the soil, methods must be repeated for many years. Continue to monitor areas for seedlings after plants have been controlled. Soil disturbance can cause a flush of seed germination. Aim to control plants before seed pods mature.

Mechanical Control

Hand pulling and digging up plants are an option for small infestations. Use a tool like a Weed Wrench, Extractigator, or Uprooter to leverage plants out of the ground, along with their roots. Check with your county noxious weed board to see if they have weed wrenches they can loan out. Chopping, cutting or mowing is an option for flat areas. Cutting plants close to the ground when they are drought stressed, late summer, can provide control on plants with stems wider than 2 inches. Monitor plants for resprouts. Cutting followed by an herbicide application on new growth can also be effective.

Biological Control

The Scotch broom seed weevil, Exapion fuscirostre, larvae feed on seeds of Scotch broom in developing seed pods. The adults also feed on flowers and the tips of stems, though their damage is not significant. The Scotch broom bruchid, Bruchidius villosus, larvae feed on developing seeds and impact the plant's reproduction. For more information about the biological control of Scotch broom, please visit WSU Extension Integrated Weed Control Project.

Herbicide Control

Cutting stems and painting the fresh cut with herbicide can provide effective control. Please refer to the PNW Weed Management Handbook, or contact your county noxious weed coordinator.


 

For more information

 
See our Written Findings for more information about Scotch broom (Cytisus scoparius).
King County Noxious Weed Control Board best management practices for Scotch broom
Whatcom County Noxious Weed Control Board Scotch broom management information
Kitsap County Noxious Weed Control Board Scotch broom information
Thurston County Noxious Weed Control Board fact sheet on Scotch broom
Report on Scotch broom from the book "Weed Control in Natural Areas in the Western United States"

Additional Photos


 
 

 


Scotch broom growth with flowers

 


Scotch broom flowers

 


Scotch broom infestation

 


Developing seed pods

 


Flowers with red markings

 


Yellow flowers

 


empty seed pods

 


Plant in bloom

 


Infestation by highway

 


growth habit example

 


infestation

 


example of compound leaves with 3 leaflets

 


developing seed pod with hairy margin

    

back to page top