Plant Assessment Form

Cordyline australis

Synonyms: Cordyline australis (G. Forst.) Endl.; Cordyline australis Endl.; Dracaena australis

Common Names: New Zealand cabbage tree; cabbage tree; Ti Kouka; giant dracaena [dracena]; dracaena palm

Evaluated on: 12/14/05

List committee review date: 10/01/2006

Re-evaluation date:

Evaluator(s)

Peter J. Warner
California Department of Parks and Recreation; CNPS; Cal-IPC
P. O. Box 603, Little River, CA 95456
(707) 937-9172 (w); (707) 937-278 (h)
pwarn@parks.ca.gov

List commitee members

Joe DiTomaso
John Randall
Peter Warner
Jake Sigg

General Comments

Based on very limited information, including only 2 reported wildland observations.

Other: Horticultural.
This plant appears best suited to moist, cool climates, perhaps augmented by summer fog and improved by overstory shading of coniferous trees, and is cold-hardy to about -10 degrees Celsius. Thus, it is unlikely that it would pose a threat to habitats in southern or inland California. However, it has not been widely reported from wildlands, despite the presence of extensive habitats for which it appears well suited, from the San Francisco Bay Area north to the Oregon state line, especially closer to the coast.

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 U Reviewed Scientific Publication
Impact?
Four-part score UCUD Total Score
C
1.2 ?Impact on plant community C. Minor Observational
1.3 ?Impact on higher trophic levels U. Unknown
1.4 ?Impact on genetic integrity D. None Other Published Material
2.1 ?Role of anthropogenic and natural disturbance in establishment A. Severe Observational
Invasiveness?
Total Points
10 Total Score C
2.2 ?Local rate of spread with no management B. Increases less rapidly Observational
2.3 ?Recent trend in total area infested within state U. Unknown Observational
2.4 ?Innate reproductive potential
(see Worksheet A)
U. Unknown Other Published Material
2.5 ?Potential for human-caused dispersal B. Moderate Observational
2.6 ? Potential for natural long-distance dispersal B. Occasional Other Published Material
2.7 ?Other regions invaded C. Already invaded Other Published Material
3.1 ?Ecological amplitude/Range
(see Worksheet C)
C. Limited Observational
Distribution?
Total Score C
3.2 ?Distribution/Peak frequency
(see Worksheet C)
D. Very low Observational

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? U Reviewed Scientific Publication
Identify ecosystem processes impacted:

No information available.


Sources of information:

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

Observed to establish as very minor component of north coast coniferous forests in Sonoma County in and adjacent to Salt Pt. State Park (1); does not appear to alter native composition of forest.
Invading disturbed and undisturbed uplifted river terrace/mixed-conifer/serpentine grassland complex, in dappled shade, Redwood National Park (Del Norte or Humboldt County) (2) Observations do not indicate any major alteration of community composition, but potential to add a new layer (sub-canopy) in small stands, or to alter riparian zone composition.


Sources of information:

1. Warner, Peter. 2002-2005. Observations at Salt Pt. State Park and Kruse Rhododendron Preserve, Sonoma Co. 707/937-9176; pwarn@parks.ca.gov
2. Williams, Andrea. 2005. Observations at Redwood National Park. 707/464-6101 x 5281; andrea_williams@nps.gov


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

No information on impacts; small, globose, blue or bluish-white berries in dense panicles (1) (similar in appearance to those of Ligustrum spp. but lighter in color) are bird-dispersed (2). No empirical or observational evidence on higher trophic impacts.


Sources of information:

1. McMinn, H. E., and E. Maino. 1963. An Illustrated Manual of Pacific Coast Trees. University of California Press, Berkeley. p. 121-122.
2. World Wildlife Fund Australia. 2005. National list of naturalized invasive and potentially invasive garden plants. http://www.wwf.org.au/News_and_Information/Publications/PDF/Conservation_guide/ListInvasivePlants.pdf


Question 1.4 Impact on genetic integrity? D Other Published Material

Extremely unlikely since no congeneric species are native to North America; genus is native to tropical regions (1). Inferential.


Sources of information:

1. McMin, H. E., and E. Maino. 1963. An Illustrated Manual of Pacific Coast Trees. University of California Press, Berkeley. p. 121-122.


Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
B Observational
Describe role of disturbance:

Disturbance does not appear to be a prerequisite site condition for germination of seeds and plant growth and development (1). Plants of many sizes (ages?) observed growing in mature forests and riparian zones (1) that do not appear to be recently disturbed (although logging may have contributed disturbance in some areas in the past). Habitat types invaded as noted in Redwood National Park (2) suggest that disturbance may facilitate germination and growth, but my observations suggest that disturbance post-digestion is not necessary for germination.


Sources of information:

1. Warner, Peter. 2002-2005. Observations at Salt Pt. State Park and Kruse Rhododendron Preserve, Sonoma Co. 707/937-9176; pwarn@parks.ca.gov
2. Williams, Andrea. 2005. Observations at Redwood National Park. 707/464-6101 x 5281; andrea_williams@nps.gov


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

Not monitored or directly observed. However, species is not native, and I estimate that the population at Salt Pt. SP numbers in the hundreds of plants, so some increase in population has occurred over an indefinite period of time. Plants probably originate from ornamental plantings, perhaps at least several decades old, at surrounding homes (ranger residences, Plantation farm, et al.) (1) Inferential.


Sources of information:

1. Warner, Peter. 2002-2005. Observations at Salt Pt. State Park and Kruse Rhododendron Preserve, Sonoma Co. 707/937-9176; pwarn@parks.ca.gov


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

Conservatively, not changing substantially; reports are limited to two that I know about. However, many forested areas between two known wildland populations could support populations that remain undetected or unreported (1). Two reports and no monitoring data are insufficient to assess area infested, especially considering the widespread planting of this taxon and the large area of potentially suitable habitat for invasion that exists between northern Sonoma County and Del Norte County. (1)


Sources of information:

1. Warner, Peter. 2002-2005. Observations at Salt Pt. State Park and Kruse Rhododendron Preserve, Sonoma Co. 707/937-9176; pwarn@parks.ca.gov


Question 2.4 Innate reproductive potential? U Other Published Material
Describe key reproductive characteristics:

Produces large numbers of small berries, with several ovules in each of 3 locules, in dense panicles (1), but otherwise, not much information found on reproductive mechanisms, structures, or success. Plants can stump-sprout following removal of stem close to base (2). Insufficient documentation upon which to base an assessment (4 unknown responses on Worksheet A).


Sources of information:

1. McMinn, H. E., and E. Maino. 1963. An Illustrated Manual of Pacific Coast Trees. University of California Press, Berkeley. p. 121-122.
2. Warner, Peter. 2002-2005. Observations at Salt Pt. State Park and Kruse Rhododendron Preserve, Sonoma Co. 707/937-9176; pwarn@parks.ca.gov


Question 2.5 Potential for human-caused dispersal? B Observational
Identify dispersal mechanisms:

Commonly sold and planted as an ornamental (1) and has been in trade for perhaps a century or more. See www.cordyline.org/ for horticultural information. No information on date of introduction into California. Continues to be planted and maintained in landscapes, increasing potential for bird dispersal of fruits into suitable wildland habitats; especially relevant along northern Calif. coast.


Sources of information:

1. Warner, Peter. 2001-2005. Observations, northern California. 707/937-9176; pwarn@parks.ca.gov
International Cordyline Society, Queensland, Australia. www.cordyline.org


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

Bird-dispersed (1) after digestion of small, globose, blue to bluish-white berries; young plants found >1km from ornamental plantings bearing flowers and fruit, but not known is distance to possible fruit-bearing trees in the wild (2). Unknown if fruits or seeds, or mature inflorescences, might float; plants can be found in riparian zones (2).


Sources of information:

1. World Wildlife Fund Australia. 2005. National list of naturalized invasive and potentially invasive garden plants. http://www.wwf.org.au/News_and_Information/Publications/PDF/Conservation_guide/ListInvasivePlants.pdf
2. Warner, Peter. 2002-2005. Observations at Salt Pt. State Park and Kruse Rhododendron Preserve, Sonoma Co. 707/937-9176; pwarn@parks.ca.gov


Question 2.7 Other regions invaded? C Other Published Material
Identify other regions:

Native to New Zealand (1). Mildly to moderately invasive in undescribed habitats in Victoria, Australia (2, 3). Invasiveness in north coastal coniferous forests in California suggest that Cordyline could invade similar types or additional stands of the same type (grand fir-, Douglas-fir-, Bishop pine-dominated forests) Conservatively, this species has invaded the only types likely, considering that it has been planted in landscapes for decades. However, observations are limited.


Sources of information:

1. Desert-Tropicals.com. 2005. Cordyline australis. http://www.desert-tropicals.com/Plants/Agavaceae/Cordyline_australis.html
2. World Wildlife Fund Australia. 2005. National list of naturalized invasive and potentially invasive garden plants. http://www.wwf.org.au/News_and_Information/Publications/PDF/Conservation_guide/ListInvasivePlants.pdf
3. The Nature Conservancy. 2005. The Global Invasive Species Initiative. Rod Randall's Big Weed List. http://tncweeds.ucdavis.edu/global/australia/aca.html


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

Observed only in forest dominated by Douglas-fir, grand fir, Bishop pine, or non-native Eucalyptus globulus (1) in or adjacent to Salt Pt. State Park, Sonoma County. Ecological types noted by Williams (2) are not sufficiently described to categorize here. Grows in riparian zones, but only within forest type noted above (1). Based on very limited observations and 2 reports.


Sources of information:

1. Warner, Peter. 2002-2005. Observations at Salt Pt. State Park and Kruse Rhododendron Preserve, Sonoma Co. 707/937-9176; pwarn@parks.ca.goventer text here
2. Williams, Andrea. 2005. Observations at Redwood National Park. 707/464-6101 x 5281; andrea_williams@nps.gov


Question 3.2 Distribution/Peak frequency? D Observational
Describe distribution:

Population distributed over several square miles in and adjacent to Salt Pt. State Park, Sonoma Co. (1), and of unknown extent at Redwood National Park (2), Del Norte or Humboldt County; not reported from other wildland areas, nor from the extensive range of similar forest types between 2 reported locations. Based on limited reports, a very low proportion of stands of this type forest have been invaded.


Sources of information:

1. Warner, Peter. 2002-2005. Observations at Salt Pt. State Park and Kruse Rhododendron Preserve, Sonoma Co. 707/937-9176; pwarn@parks.ca.goventer text here
2. Williams, Andrea. 2005. Observations at Redwood National Park. 707/464-6101 x 5281; andrea_williams@nps.gov


Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less No
Dense infestations produce >1,000 viable seed per square meter Unknown
Populations of this species produce seeds every year. Unknown
Seed production sustained over 3 or more months within a population annually No
Seeds remain viable in soil for three or more years Unknown
Viable seed produced with both self-pollination and cross-pollination Unknown
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: 1
Total unknowns: 4
Total score: U?

Related traits:

Seeds may require digestion or other means of treatment for germination, based on inferences from observations. Large amount of seed production possible, but viability and fecundity are unknown.

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 scrub
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrub
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
chaparral
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairie
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 forest
riparian woodland
riparian scrub (incl.desert washes)
Woodlandcismontane woodland
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forest
North Coast coniferous forestD, < 5%
closed cone coniferous forestD, < 5%
lower montane coniferous forest
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth): C
Distribution (highest score): D

Infested Jepson Regions

Click here for a map of Jepson regions

  • Central West
  • Northwest
  • Southwest