Plant Assessment Form

Colocasia esculenta

Synonyms: Arum esculentum; Caladium esculentum; Colocasia antiquorum

Common Names: taro root; wild taro; coco-yam; eddo; elephant-ear-plant

Evaluated on: 20-Dec-16

List committee review date: 25/01/2017

Re-evaluation date:

Evaluator(s)

Mona Robison/Science Program Manager
Cal-IPC
916-802-2004
rrobison@cal-ipc.org

List commitee members

Elizabeth Brusati
Tim Hyland
Eric Wrubel
Irina Irvine
Holly Forbes

General Comments

No general comments for this species

Table 2. Criteria, Section, and Overall Scores

Overall Score? Moderate
Alert Status? Alert
Documentation? 3 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes B Reviewed Scientific Publication
Impact?
Four-part score BBUD Total Score
B
1.2 ?Impact on plant community B. Moderate Reviewed Scientific Publication
1.3 ?Impact on higher trophic levels U. Unknown No Information
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
Invasiveness?
Total Points
17 Total Score A
2.2 ?Local rate of spread with no management B. Increases less rapidly Observational
2.3 ?Recent trend in total area infested within state A. Increasing rapidly Observational
2.4 ?Innate reproductive potential
(see Worksheet A)
B. Moderate Reviewed Scientific Publication
2.5 ?Potential for human-caused dispersal A. High Other Published Material
2.6 ? Potential for natural long-distance dispersal A. Frequent Other Published Material
2.7 ?Other regions invaded B. Invades 1 or 2 ecological types Other Published Material
3.1 ?Ecological amplitude/Range
(see Worksheet C)
D. Narrow Other Published Material
Distribution?
Total Score D
3.2 ?Distribution/Peak frequency
(see Worksheet C)
D. Very low Other Published Material

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? B Reviewed Scientific Publication
Identify ecosystem processes impacted:

Vegetative growth leads to dense populations and its large leaves shade out native vegetation. Since light restriction is considered an abiotic impact, the question was answered as Moderate.


Sources of information:

Weber 2003


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

Forms dense growth along river and lake shores, displacing native shoreline vegetation. Vegetative growth leads to dense populations and its large leaves shade out native vegetation. Colocasia esculenta can tolerate a wide range of wet to dry sites. It easily invades wetland edges, swamps, backwater streams and riverine forests. Colocasia esculenta can form dense stands out-competing native plants. In south-eastern Queensland, it invades waterways and wetlands and replaces native aquatic plants.
Extensive stands alter the vegetational structure and dynamics of riparian plant communities. Vegetative growth leads to dense populations and large leaves shade out native vegetation. Grows 1m to 2.5m tall.

C. esculenta grows along the edge of the river and along The Meadows Slough mixed with other riparian vegetation, including the State-listed Rare California hibiscus (Hibiscus lasiocarpus var. occidentalis). This will make control of the C. esculenta difficult in some of the area as management of C. esculenta would conflict with the persistence of California hibiscus (Robison pers. comm.).


Sources of information:

Langeland and Burks 2008
Weber 2003
Invasive Plant Atlas 2016
Queensland Biosecurity 2016
Robison, R. Personal communication.


Question 1.3 Impact on higher trophic levels? U No Information
Identify type of impact or alteration:

There is no information available on the impacts of C. esculenta on higher trophic levels in California or elsewhere.


Sources of information:

Question 1.4 Impact on genetic integrity? D Reviewed Scientific Publication

No known hybridization occurs with native species. There are no native Colocasia species in California and few members of the Araceae in California with similar floral structure which it could hybridize with.


Sources of information:

Jepson eFlora 2016


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

C. esculenta is introduced through cultivation and after introduction can spread on its own along river banks and in wetlands. Flooding is also a means of establishment.


Sources of information:

Langeland and Burks 2008
Weber 2003
CABI 2017
Wagner 1999


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

Colocasia esculenta was first collected and verified as occurring naturally in California in 2014 (CCH 2014). The exact introduction date is unknown, but the species has been grown as a crop in California in past years (Molinar and Yang 2001, Moore and Lawrence 2003). There has been no known management in the introduction area since 2014 and the natural resources manager of Delta Meadows State Park reports that it has been observed to spread less than a mile upstream.


Sources of information:

Calflora 2016
CCH 2016
Molinar and Yang 2001
Moore and Lawrence 2003
Beard, D. Personal communication


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

Colocasia esculenta was first collected and verified as occurring naturally in California in 2014 (CCH 2014). The exact introduction date is unknown, but the species has been grown as a crop in California in past years (Molinar and Yang 2001, Moore and Lawrence 2003). There has been no known management in the introduction area since 2014 and the natural resources managers of Delta Meadows State Park reports that it has been observed to spread less than a mile upstream, and the population is expanding enough to be considered doubling in 10 years (Beard, D. and Allen, C. personal communications). After the first detection at Delta Meadows, populations were reported in San Joaquin, Solano and Orange counties, so it is assumed that the plant will be spreading and found elsewhere over time.


Sources of information:

Calflora 2016
CCH 2016
Molinar and Yang 2001
Moore and Lawrence 2003
Allen, C. Personal communication.
Beard, D. Personal communication.


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

Like most other root and tuber crops, taro is vegetatively propagated, although seed production is possible. Natural breeding and population spread have been reported for wild taro. Cultivars are propagated through the use of corms, cormels (also known as suckers), while vegetative propagation occurs through stolons in the wild. According to Weber (2003), naturalized plants rarely produce seeds and only in hot, tropical climates.


Sources of information:

Chair 2016
Weber 2003


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

Dispersed primarily by purposeful or accidental movement of vegetative fragments. Only a portion of corm crown and petiole are needed to establish a new plant. C. esculenta has been grown as a crop in California in past years (Molinar and Yang 2001, Moore and Lawrence 2003).


Sources of information:

Langeland and Burks 2008
Molinar and Yang 2001
Moore and Lawrence 2003


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

Rhizome fragments are carried by streams. Grows mostly next to rivers so there is high potential for long-distance dispersal. Floods can dislodge bud-laden rhizomes from the banks. Growth seems to be best in the silty soils lining the river-banks.


Sources of information:

Langeland and Burks 2008
Weber 2003


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

C. esculenta is native to Australia, India, and southeastern Asia. It is naturalized in Florida, New Zealand, West Indies, southern Europe, and the Canary Islands, mainly in tropical climates. It can be found growing mainly in moist forests and wet areas in riparian habitats, riverbanks, along streams, marshes, and canals. It can also be found in secondary forests, roadsides, and disturbed areas near to abandoned crop fields. It has invaded some of these habitat types in California, but is not yet found in woodlands or riparian habitats away from the immediate water's edge, and has not yet spread widely.


Sources of information:

Langeland and Burks 2008
Calflora 2016
Wagner et al. 1999


Section 3: Distribution
Question 3.1 Ecological amplitude/Range? D Other Published Material

Colocasia esculenta was first collected and verified as occurring naturally in California in 2014 (CCH 2014). The exact introduction date is unknown, but the species has been grown as a crop in California in past years (Molinar and Yang 2001, Moore and Lawrence 2003). A specimen was collected from Delta Meadows State Park in 2014, located near Isleton in Sacramento County. Plants were growing along the edge of the river and in The Meadows Slough mixed with other riparian vegetation, including the State-listed Rare California hibiscus (Hibiscus lasiocarpus var. occidentalis). Further mapping in the area identified it as occurring in 7 patches in the Park as well as upstream and downstream from the Park boundary in two places (Robison 2014). Other reports were submitted to Calflora for locations in Solano, San Joaquin and Orange counties (Calflora 2016). The locations in Solano and San Joaquin counties are on river edges, the Orange County habitat is unknown, but appears to be a wetland edge from the aerial photograph.


Sources of information:

CCH 2014
Calflora 2016
Molinar and Yang 2001
Moore and Lawrence 2003
Robison 2014


Question 3.2 Distribution/Peak frequency? D Other Published Material
Describe distribution:

Occurs along river and slough edges in the Sacramento and San Joaquin delta. In Orange County it is growing along the shaded, moist edge of a small drainage, probably fed by urban runoff, but in a native plant community. Probably best described as a light riparian area (Vanderhoff, R. pers. comm.).


Sources of information:

CCH 2014
Calflora 2016
Robison 2014
Vanderhoff, R. Personal communication.


Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less Yes
Dense infestations produce >1,000 viable seed per square meter No
Populations of this species produce seeds every year. No
Seed production sustained over 3 or more months within a population annually Unknown
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 Yes
Fragments easily and fragments can become established elsewhere Yes
Resprouts readily when cut, grazed, or burned Yes
Total points: 5
Total unknowns: 3
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
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 swampD, < 5%
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 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): D
Distribution (highest score): D

Infested Jepson Regions

Click here for a map of Jepson regions