Plant Assessment Form

Cytisus scoparius

Synonyms: Sarathamnus scoparius, Spartium scoparius

Common Names: Scotch broom; English broom; common broom

Evaluated on: 3/18/05

List committee review date: 08/07/2005

Re-evaluation date:

Evaluator(s)

Carla Bossard
St. Mary's College of California
401 Del Oro Av, Davis CA
(925) 631-4032
cbossard@stmarys-ca.edu
Elizabeth Brusati
California Invasive Plant Council
1442-A Walnut St. #462, Berkeley, CA 94709
(510) 843-3902
edbrusati@cal-ipc.org

List commitee members

Carla Bossard
John Randall
Carri Pirosko
Dan Gluesenkamp
Gina Skurka
Brianna Richardson

General Comments

No general comments for this species

Table 2. Criteria, Section, and Overall Scores

Overall Score? High
Alert Status? No Alert
Documentation? 3.5 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes A Reviewed Scientific Publication
Impact?
Four-part score AAAD Total Score
A
1.2 ?Impact on plant community A. Severe Reviewed Scientific Publication
1.3 ?Impact on higher trophic levels A. Severe Reviewed Scientific Publication
1.4 ?Impact on genetic integrity D. None Other Published Material
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Reviewed Scientific Publication
Invasiveness?
Total Points
14 Total Score B
2.2 ?Local rate of spread with no management A. Increases rapidly Other Published Material
2.3 ?Recent trend in total area infested within state B. Increasing less rapidly Observational
2.4 ?Innate reproductive potential
(see Worksheet A)
A. High Reviewed Scientific Publication
2.5 ?Potential for human-caused dispersal B. Moderate Other Published Material
2.6 ? Potential for natural long-distance dispersal C. Rare Reviewed Scientific Publication
2.7 ?Other regions invaded C. Already invaded Reviewed Scientific Publication
3.1 ?Ecological amplitude/Range
(see Worksheet C)
A. Widespread Observational
Distribution?
Total Score A
3.2 ?Distribution/Peak frequency
(see Worksheet C)
B. Moderate Anecdotal

Table 3. Documentation

Scores are explained in the "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands".

Section 1: Impact
Question 1.1 Impact on abiotic ecosystem processes? A Reviewed Scientific Publication
Identify ecosystem processes impacted:

Nitrogen-fixing species. Can acidify the soil. Carries fire to the tree canopy, increasing frequency and duration of fires.


Sources of information:

1. Bossard, C. 2000. Cytisus scoparius. pp. 145-150 in Bossard, C., J. Randall, and M. Hochovsky. (eds). Invasive Plants of California's Wildlands. University of Califonria Press, Berkeley, CA


Question 1.2 Impact on plant community composition,
structure, and interactions?
A Reviewed Scientific Publication
Identify type of impact or alteration:

Lower vegetation dies out beneath mature bushes, leading to widespread loss of herbaceous plants and tree seedlings (1). Displaces native species and forms monospecific stands in California (2). Native communities are not monospecific


Sources of information:

Smith J.M.B., Halen R.L. 1991. Preliminary Observations on the Seed Dynamics of Broom (Cytisus scoparius) at Barrington Tops, New South Wales. Plant Protection Quarterly 6(2):73-78.
2. Bossard, C. 2000. Cytisus scoparius. pp. 145-150 in Bossard, C., J. Randall, and M. Hochovsky. (eds). Invasive Plants of California's Wildlands. University of Califonria Press, Berkeley, CA


Question 1.3 Impact on higher trophic levels? A Reviewed Scientific Publication
Identify type of impact or alteration:

Seeds are toxic to ungulates. Mature shoots are unpalatable and are not used by forage except by rabbits in the seedling stage. Less food for native species of animals


Sources of information:

1. Bossard, C. 2000. Cytisus scoparius. pp. 145-150 in Bossard, C., J. Randall, and M. Hochovsky. (eds). Invasive Plants of California's Wildlands. University of Califonria Press, Berkeley, CA


Question 1.4 Impact on genetic integrity? D Other Published Material

No native Cytisus None known


Sources of information:

Hickman, J. C. (ed.) 1993. The Jepson Manual, Higher Plants of California. University of California Press. Berkeley, CA


Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
A Other Published Material
Describe role of disturbance:

Soil disturbance from road and home construction; timber harvest; road side machinery (1). Inhabits a wide range of disturbed and undisturbed habitats. Plants establish best after soil or vegetation disturbance, such as fire or herbicide treatment. However, they can invade vegetation without major disturbance if open microsites are available (2). Seedlings in the native range in France survived better in disturbed plots than undisturbed ones (3). These increase establishment of brooms


Sources of information:

Question 2.2 Local rate of spread with no management? A Other Published Material
Describe rate of spread:

1 to 1.5 m / year in undisturbed annual grasslands Spreads rapidly especially when many foci of infection are present


Sources of information:

1. Bossard, C. 2000. Cytisus scoparius. pp. 145-150 in Bossard, C., J. Randall, and M. Hochovsky. (eds). Invasive Plants of California's Wildlands. University of California Press, Berkeley, CA


Question 2.3 Recent trend in total area infested within state? B Observational
Describe trend:

Still spreading but not rapidly Many suitable habitats are already occupied by broom


Sources of information:

Carla Bossard, St. Mary's College of California, personal observation


Question 2.4 Innate reproductive potential? A Reviewed Scientific Publication
Describe key reproductive characteristics:

Perennial shrub. Becomes reproductive at two to three years and can live up to 17 years in California, longer than in its native range. Has long-lasting seed bank. A mature plant can produce up to 12,000 seeds that create a seedbank of 2000 seeds/sq ft and remain viable for five years (1). Seeds remain dormant for years (2). Can resprout after cutting or fire (3). Variability in the duration between seed deposition and germination (4, 5) provides C. scoparius with considerable flexibility for coping with the fluctuations in precipitation and temperature that are typical in California (4).


Sources of information:

1. Bossard, C. 2000. Cytisus scoparius. pp. 145-150 in Bossard, C., J. Randall, and M. Hochovsky. (eds). Invasive Plants of California's Wildlands. University of California Press, Berkeley, CA.
2. Smith J.M.B., Halen R.L. 1991. Preliminary Observations on the Seed Dynamics of Broom (Cytisus scoparius) at Barrington Tops, New South Wales. Plant Protection Quarterly 6(2):73-78.
3. Bossard C.C., Rejmanek M. 1994. Herbivory, Growth, Seed Production, and Resprouting of an Exotic Invasive Shrub, Cytisus scoparius. Biological Conservation 67:193-200.
4. Bossard C. 1993. Seed Germination in the Exotic Shrub Cytisus scoparius (Scotch Broom) in California. Madrono 40(1):47-61.
5. Sheppard A.W., et al. 2002. Factors affecting the invasion and persistence of broom Cytisus scoparius in Australia. Journal of Applied Ecology 39: 721-734.


Question 2.5 Potential for human-caused dispersal? B Other Published Material
Identify dispersal mechanisms:

Seeds attach to road equipment (1). Sold as an ornamental (2).


Sources of information:

1. Bossard, C. 2000. Cytisus scoparius. pp. 145-150 in Bossard, C., J. Randall, and M. Hochovsky. (eds). Invasive Plants of California's Wildlands. University of California Press, Berkeley, CA.
2. Isaacson, D. L. 2000. Impacts of broom (Cytisus scoparius) in western North America. Plant Protection Quarterly 15(4): 145-148.


Question 2.6 Potential for natural long-distance dispersal? C Reviewed Scientific Publication
Identify dispersal mechanisms:

Ants and ballistic seeds disperse short distances (1). Seeds also disperse with rainwash (2), but long distance movement is probably very uncommon.


Sources of information:

1. Bossard C.C. 1991. The Role of Habitat Disturbance, Seed Predation and Ant Dispersal on Establishment of the Exotic Shrub Cytisus scaparius in California. American Midland Naturalist 126: 1-13.
2. Bossard, C. 2000. Cytisus scoparius. pp. 145-150 in Bossard, C., J. Randall, and M. Hochovsky. (eds). Invasive Plants of California's Wildlands. University of California Press, Berkeley, CA


Question 2.7 Other regions invaded? C Reviewed Scientific Publication
Identify other regions:

Canada, Australia (Smith), New Zealand and India Scoring as C because many suitable habitats already occupied by broom (see 2.3).


Sources of information:

Bossard, C. 2000. Cytisus scoparius. pp. 145-150 in Bossard, C., J. Randall, and M. Hochovsky. (eds). Invasive Plants of California's Wildlands. University of California Press, Berkeley, CA
Smith J.M.B., Halen R.L. 1991. Preliminary Observations on the Seed Dynamics of Broom (Cytisus scoparius) at Barrington Tops, New South Wales. Plant Protection Quarterly 6(2):73-78.


Section 3: Distribution
Question 3.1 Ecological amplitude/Range? A Observational

As of 2000, occupied >700,000 acres in central to northwest coastal and Sierra Foothill regions. Present along the coast from Monterey to the Oregon border, prevalent in interior mountains of northern California on lower slopes and very prevalent in Eldorado, Nevada, and Placer counties in the Sierra Nevada foothills (2).


Sources of information:

1. Bossard, C. 2000. Cytisus scoparius. pp. 145-150 in Bossard, C., J. Randall, and M. Hochovsky. (eds). Invasive Plants of California's Wildlands. University of Califonria Press, Berkeley, CA.


Question 3.2 Distribution/Peak frequency? B Anecdotal
Describe distribution:

See table


Sources of information:

Carla Bossard, St. Mary's College of California, personal observation


Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less No
Dense infestations produce >1,000 viable seed per square meter Yes
Populations of this species produce seeds every year. Yes
Seed production sustained over 3 or more months within a population annually No
Seeds remain viable in soil for three or more years Yes
Viable seed produced with both self-pollination and cross-pollination No
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes No
Fragments easily and fragments can become established elsewhere No
Resprouts readily when cut, grazed, or burned Yes
Total points: 6
Total unknowns: 0
Total score: A?

Related traits:

Worksheet B - Arizona Ecological Types is not included here

Worksheet C - California Ecological Types

(sensu Holland 1986)
Major Ecological Types Minor Ecological Types Code?
Marine Systemsmarine systems
Freshwater and Estuarine lakes, ponds, reservoirs
Aquatic Systemsrivers, streams, canals
estuaries
Dunescoastal
desert
interior
Scrub and Chaparralcoastal bluff scrub
coastal scrubB, 20% - 50%
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrub
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
chaparralD, < 5%
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairieD, < 5%
valley and foothill grassland
Great Basin grassland
vernal pool
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swamp
Riparian and Bottomland habitatriparian forestD, < 5%
riparian woodland
riparian scrub (incl.desert washes)
Woodlandcismontane woodlandC, 5% - 20%
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forest
North Coast coniferous forestB, 20% - 50%
closed cone coniferous forest
lower montane coniferous forestD, < 5%
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth): A
Distribution (highest score): B

Infested Jepson Regions

Click here for a map of Jepson regions

  • CA Floristic Province
  • Cascade Range
  • Central West
  • Great Valley
  • Northwest
  • Sierra Nevada
  • Southwest
  • Modoc Plateau
  • Mojave Desert