Plant Assessment Form

Robinia pseudoacacia

Common Names: black locust

Evaluated on: 12/22/04

List committee review date: 11/03/2005

Re-evaluation date:


Elizabeth Brusati, project manager
California Invasive Plant Council
1442A Walnut St. #462, Berkeley, CA 94709

List committee members

Joe DiTomaso
John Randall
Carla Bossard

General Comments

No general comments for this species

Table 2. Criteria, Section, and Overall Scores

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

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? C Reviewed Scientific Publication
Identify ecosystem processes impacted:

Nitrogen cycling, light availability. However, infestations in California are too small to have these effects. Nitrogen-fixing tree that increases the concentration of NO3 in the soil. Fixed N is accumulated as biomass and enters the soil only in older (38yr) stands (1). Tall tree (100 ft), so creates shade where it invades open areas

Sources of information:

1. Boring L. R., Swank W. T. 1984. The Role of Black Locust (Robinia pseudoacacia) in Forest Succession. Journal of Ecology. 72: 749-766.
2. Hunter, J. Robinia pseudoacacia. pp. 273-276 in Bossard, C. M., J. M. Randall, and M. C. Hoshovsky (ed.) Invasive plants of California's wildlands. University of California Press. Berkeley, CA.

Question 1.2 Impact on plant community composition,
structure, and interactions?
C Other Published Material
Identify type of impact or alteration:

Displaces native vegetation (1) but forms only patches in California.

Sources of information:

1. Hunter 2000

Question 1.3 Impact on higher trophic levels? U
Identify type of impact or alteration:

Poisonous to livestock but they rarely eat it. No information on impacts to native species.

Sources of information:

1. Kingsbury J. M. 1964. Poisonous Plants of the United Sates and Canada. Prentice Hall Inc. New Jersey.

Question 1.4 Impact on genetic integrity? D Reviewed Scientific Publication

Possibility of hybridization with one related native tree (R. neomexicana) but this seems unlikely because the native inhabits drier areas and is uncommon, and R. pseudoacacia reproduces mostly by suckers rather than seed. One closely-related California native

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?
Describe role of disturbance:

Needs open areas for colonization . Early successional species that grows best on clear-cuts, abandoned pastures, or roadsides (1). Can invade undisturbed sand prairies (2).

Sources of information:

1. Boring and Swank 1984
2. Converse C. K. 1984 Elemental Species Abstract for Robinia pseudoacacia, The Nature Conservancy. Washington, D. C.

Question 2.2 Local rate of spread with no management? C
Describe rate of spread:

This species has been in California for many years but has not spread significantly.

Sources of information:

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

Consensus of weed committee is that populations in California are stable.

Sources of information:

Question 2.4 Innate reproductive potential? B
Describe key reproductive characteristics:

Can reproduce from seeds, but mostly reproduces by suckers or sprouting from roots. Can grow to 8m within 3 yrs (1). Begins producing seeds at year 6, with best crops between ages 15-40. Heavy seed crops at 1-2 year intervals, and light crops in between. Produces 16,000 - 35,000 per pound of seed pods. Seedling reproduction is rare (2). Seeds disperse by wind or gravity (3)

Sources of information:

1. Boring and Swank 1984
2. Roach B. A. 1958 Silvical Characteristics of Black Locust. U. S. Department of Agriculture Forest Service. 1-15.
3. Hunter 2000

Question 2.5 Potential for human-caused dispersal? A Reviewed Scientific Publication
Identify dispersal mechanisms:

Planted for cultivation (1, 2) and landscaping. Has been used for panelling, construction, firewood, fenceposts, livestock forage, and nectar for honey production (2).

Sources of information:

1. Hunter 2000
2. Roach 1958

Question 2.6 Potential for natural long-distance dispersal? C Other Published Material
Identify dispersal mechanisms:

Some seeds dispersed by wind, but as most reproduction is by suckers, this is probably a limited means of dispersal.

Sources of information:

1. Hunter 2000
2. Roach 1958

Question 2.7 Other regions invaded? C Observational
Identify other regions:

Cultivated as a horticultural species, but rarely escapes.

Sources of information:

Joe DiTomaso, UC Davis, and John Randall, The Nature Conservancy Invasive Species Initiative, pers. Obs.

Section 3: Distribution
Question 3.1 Ecological amplitude/Range? A Reviewed Scientific Publication

Mostly inhabits disturbed sites. Early successional species, needs open areas (1). Invades dry prairies, sand prairies and savannas (2). Widespread in northern California below 6300 ft, also common in Great Basin area (3). Found in disturbed woodlands and ravines in Tahoe National Forest and John Muir National Monument (4).

Sources of information:

1. Boring and Swank 1984
2. Converse 1984
3. Hickman 1993
4. Hunter 2000

Question 3.2 Distribution/Peak frequency? D Reviewed Scientific Publication
Describe distribution:

Present only in small patches in California.

Sources of information:

Joe DiTomaso, UC Davis, and John Randall, The Nature Conservancy Invasive Species Initiative, pers.obs.

Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less No
Dense infestations produce >1,000 viable seed per square meter No
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 Unknown
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes Yes
Fragments easily and fragments can become established elsewhere No
Resprouts readily when cut, grazed, or burned Yes
Total points: 5
Total unknowns: 1
Total score: B?

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
Scrub and Chaparralcoastal bluff scrub
coastal scrub
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrub
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairieD, < 5%
valley and foothill grasslandD, < 5%
Great Basin grasslandD, < 5%
vernal pool
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swamp
Riparian and Bottomland habitatriparian forest
riparian woodlandD, < 5%
riparian scrub (incl.desert washes)
Woodlandcismontane woodland
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forest
North Coast coniferous forest
closed cone coniferous forest
lower montane coniferous forest
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth): B
Distribution (highest score): D

Infested Jepson Regions

Click here for a map of Jepson regions

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