Research directed by C. Daehler (UH Botany) with funding from the Kaulunani Urban Forestry Program and US Forest Service

Information on Risk Assessments
Original risk assessment

Dieffenbachia seguine (Jacq.) Schott = D. amoena = D. maculata; Dieffenbachia picta, dumbcane, zebra plant

Answer

1.01

Is the species highly domesticated?

y=-3, n=0

n

1.02

Has the species become naturalized where grown?

y=-1, n=-1

y

1.03

Does the species have weedy races?

y=-1, n=-1

n

2.01

Species suited to tropical or subtropical climate(s) (0-low; 1-intermediate; 2-high) – If island is primarily wet habitat, then substitute “wet tropical” for “tropical or subtropical”

See Append 2

2

2.02

Quality of climate match data (0-low; 1-intermediate; 2-high) see appendix 2

2

2.03

Broad climate suitability (environmental versatility)

y=1, n=0

n

2.04

Native or naturalized in regions with tropical or subtropical climates

y=1, n=0

y

2.05

Does the species have a history of repeated introductions outside its natural range? y=-2

?=-1, n=0

y

3.01

Naturalized beyond native range y = 1*multiplier (see Append 2), n= question 2.05

y

3.02

Garden/amenity/disturbance weed y = 1*multiplier (see Append 2)

n=0

n

3.03

Agricultural/forestry/horticultural weed y = 2*multiplier (see Append 2)

n=0

3.04

Environmental weed y = 2*multiplier (see Append 2)

n=0

y

3.05

Congeneric weed y = 1*multiplier (see Append 2)

n=0

n

4.01

Produces spines, thorns or burrs

y=1, n=0

n

4.02

Allelopathic

y=1, n=0

n

4.03

Parasitic

y=1, n=0

n

4.04

Unpalatable to grazing animals

y=1, n=-1

y

4.05

Toxic to animals

y=1, n=0

y

4.06

Host for recognized pests and pathogens

y=1, n=0

y

4.07

Causes allergies or is otherwise toxic to humans

y=1, n=0

y

4.08

Creates a fire hazard in natural ecosystems

y=1, n=0

n

4.09

Is a shade tolerant plant at some stage of its life cycle

y=1, n=0

y

4.1

Tolerates a wide range of soil conditions (or limestone conditions if not a volcanic island)

y=1, n=0

y

4.11

Climbing or smothering growth habit

y=1, n=0

n

4.12

Forms dense thickets

y=1, n=0

n

5.01

Aquatic

y=5, n=0

n

5.02

Grass

y=1, n=0

n

5.03

Nitrogen fixing woody plant

y=1, n=0

n

5.04

Geophyte (herbaceous with underground storage organs -- bulbs, corms, or tubers)

y=1, n=0

n

6.01

Evidence of substantial reproductive failure in native habitat

y=1, n=0

n

6.02

Produces viable seed.

y=1, n=-1

n

6.03

Hybridizes naturally

y=1, n=-1

6.04

Self-compatible or apomictic

y=1, n=-1

6.05

Requires specialist pollinators

y=-1, n=0

y

6.06

Reproduction by vegetative fragmentation

y=1, n=-1

y

6.07

Minimum generative time (years) 1 year = 1, 2 or 3 years = 0, 4+ years = -1

See left

7.01

Propagules likely to be dispersed unintentionally (plants growing in heavily trafficked areas)

y=1, n=-1

y

7.02

Propagules dispersed intentionally by people

y=1, n=-1

y

7.03

Propagules likely to disperse as a produce contaminant

y=1, n=-1

n

7.04

Propagules adapted to wind dispersal

y=1, n=-1

n

7.05

Propagules water dispersed

y=1, n=-1

n

7.06

Propagules bird dispersed

y=1, n=-1

n

7.07

Propagules dispersed by other animals (externally)

y=1, n=-1

n

7.08

Propagules survive passage through the gut

y=1, n=-1

n

8.01

Prolific seed production (>1000/m2)

y=1, n=-1

n

8.02

Evidence that a persistent propagule bank is formed (>1 yr)

y=1, n=-1

n

8.03

Well controlled by herbicides

y=-1, n=1

8.04

Tolerates, or benefits from, mutilation, cultivation, or fire

y=1, n=-1

y

8.05

Effective natural enemies present locally (e.g. introduced biocontrol agents)

y=-1, n=1

Total score:

7

1.01

no evidence

1.02

(1)In Fiji, "sometimes becoming a minor weed of waste places, roadsides, and coconut plantations" (Smith, 1979). [Fiji] (2)Dieffenbachia maculata - cultivated and escaped in Puerto Rico (3)Cultivated and completely naturalized around pond margins, and in ditches and wet bottom pastures

(1)http://www.hear.org/pier/species/dieffenbachia_seguine.htm (2)Liogier, H.A. and Martorell, L.F. 1982. Flora of Puerto Rico and adjacent islands. Editorial de la Universidad de Puerto Rico, Rio Piedras (3)Adams, C.D. 1972. Flowering Plants of Jamaica, University of the West Indies, Mona

1.03

There are many cultivars, but no information about whether the invasive populations belong to particular cultivars

http://www.ars-grin.gov/npgs/cgc_reports/herbscgc1995.htm

2.01

Native:
NORTHERN AMERICA
Mexico [s.]
SOUTHERN AMERICA
Mesoamerica: Costa Rica; El Salvador; Guatemala; Honduras; Nicaragua
Caribbean: Antigua and Barbuda; Dominica; Grenada; Guadeloupe; Martinique; Puerto Rico; St. Lucia; St. Vincent and Grenadines; Trinidad and Tobago
Northern South America: French Guiana; Guyana; Suriname; Venezuela [n.]
Western South America: Colombia; Ecuador - Esmeraldas
Other: cultivated elsewhere

USDA, ARS, National Genetic Resources Program.
Germplasm Resources Information Network - (GRIN) [Online Database].
National Germplasm Resources Laboratory, Beltsville, Maryland.
URL: http://www.ars-grin.gov/var/apache/cgi-bin/npgs/html/taxon.pl?13948 (30 June 2004)

2.02

2.03

(1)Hardiness Range 10B to 11; Protect from drafts and temperatures below 60 degrees F (2)High humidity. (3)0-1000 ft [300 m]

(1)Horticopia A-Z.Horticopia, Inc., Purcellville, VA. ISBN 1-887215-07-7. (2)http://www.tropilab.com/dumbcane.html [wet lowland rainforest] (3)(3)Adams, C.D. 1972. Flowering Plants of Jamaica, University of the West Indies, Mona

2.04

Native:
NORTHERN AMERICA
Mexico [s.]
SOUTHERN AMERICA
Mesoamerica: Costa Rica; El Salvador; Guatemala; Honduras; Nicaragua
Caribbean: Antigua and Barbuda; Dominica; Grenada; Guadeloupe; Martinique; Puerto Rico; St. Lucia; St. Vincent and Grenadines; Trinidad and Tobago
Northern South America: French Guiana; Guyana; Suriname; Venezuela [n.]
Western South America: Colombia; Ecuador - Esmeraldas
Other: cultivated elsewhere

USDA, ARS, National Genetic Resources Program.
Germplasm Resources Information Network - (GRIN) [Online Database].
National Germplasm Resources Laboratory, Beltsville, Maryland.
URL: http://www.ars-grin.gov/var/apache/cgi-bin/npgs/html/taxon.pl?13948 (30 June 2004)

2.05

"widely and commonly cultivated for its variegated leaves"

Whistler, A.W. (2000) Tropical Ornamentals: A Guide. Timber Press, Inc., Portland, Oregon. 542pp. p.178

3.02

no evidence

3.03

In Fiji, "sometimes becoming a minor weed of waste places, roadsides, and coconut plantations" (Smith, 1979). [Fiji, not recognized as a significant economic weed]

http://www.hear.org/pier/species/dieffenbachia_seguine.htm

3.04

"A number of large infestations of Dieffenbachia seguine (spotted dieffenbachia or dumb cane), a common house and yard plant, were noted in the Vailima Reserve and elsewhere, particularly in stream bottoms and other moist areas. This species has become a problem in American Samoa and is reportedly present in the Cook Islands, Fiji and French Polynesia. Where found in natural areas this species should be removed, as it reproduces vegetatively and can thrive in the dense shade of an intact native forest canopy, crowding out other species."

http://www.hear.org/pier/reports/sreport.htm

3.05

no evidence

4.01

no description of these traits

Whistler, A.W. (2000) Tropical Ornamentals: A Guide. Timber Press, Inc., Portland, Oregon. 542pp. p.178

4.02

no evidence

4.03

no evidence

4.04

The stems of dumbcane were used as prods to control cattle. It did not take too many pokes with the irritating ramrod to force a recalcitrant cow back to its own pasture. [cattle avoid this plant]

http://www.killerplants.com/herbal-folklore/20020325.asp

4.05

suffocation, kidney failure, death.

http://www.petroglyphsnm.org/petperil.pdf

4.06

taro feathery mosaic disease -- "Among the 33 plant spp. mechanically inoculated with sap from infected Colocasia esculenta, Typhonium trilobatum, Dieffenbachia maculata, D. sp., and Datura metel were highly susceptible while Xanthosoma sp. was moderately susceptible. " [a specialist pest of taro horticulture]

(1) Palomar, M. K. Duatin, J. Y. Palermo, V. G. (1984) Araceous and nonaraceous hosts of taro feathery mosaic disease.Annals of Tropical Research, 1984, Vol. 6, pp. 33-41, 5 ref.
(2) http://www.fao.org/DOCREP/005/AC450E/ac450e06.htm

4.07

(1) "All parts of the plant are poisonous if ingested"
(2) "The name dumbcane is derived from th effect of the calcium oxalate crystals in the the plant's irritating sap, which when ingested cause paralysis and swelling of the tongue, silencing the person, and even causing death in children and animals." (3)Listed as 'Milder discouragement - poisonous but not toxic' (4)Care should be taken around dumbcanes, but seldom is there actual ingestion. The pain is immediate; the tongue and lining of the mouth swell and the vocal cords become paralyzed. Propagating the plants from cuttings can cause a rather nasty rash if the sap contacts the skin.

(2) Whistler, A.W. (2000) Tropical Ornamentals: A Guide. Timber Press, Inc., Portland, Oregon. 542pp. p.178 (3)http://www.life.umd.edu/classroom/BSCI124/lec30.html (4)http://www.killerplants.com/herbal-folklore/20020325.asp

4.08

Moisture: Moist [need moist environment to grow]

Horticopia A-Z.Horticopia, Inc., Purcellville, VA. ISBN 1-887215-07-7.

4.09

Exposure Full shade to partial sun

Horticopia A-Z.Horticopia, Inc., Purcellville, VA. ISBN 1-887215-07-7.

4.1

Soil Condition Loamy, sandy, clay, acidic, neutral, tolerates some salt

Horticopia A-Z.Horticopia, Inc., Purcellville, VA. ISBN 1-887215-07-7.

4.11

Upright or erect perennial

Horticopia A-Z.Horticopia, Inc., Purcellville, VA. ISBN 1-887215-07-7.

4.12

no evidence

5.01

Soil Condition: Loamy, sandy, clay, acidic, neutral, tolerates some salt

Horticopia A-Z.Horticopia, Inc., Purcellville, VA. ISBN 1-887215-07-7.

5.02

perennial, Araceae

5.03

Perennial

Horticopia A-Z.Horticopia, Inc., Purcellville, VA. ISBN 1-887215-07-7.

5.04

Upright or erect perennial

Horticopia A-Z.Horticopia, Inc., Purcellville, VA. ISBN 1-887215-07-7.

6.01

"Because it is able to grow and reproduce under low light conditions, it can invade undisturbed forests."

http://www.hear.org/pier/species/dieffenbachia_seguine.htm

6.02

(1) "The most popular Dieffenbachia cultivars are propagated asexually either via tissue culture or by tip cuttings. There are no seed propagated varieties."
(2) "Fruit a globose red-oragnge berry, infrequently formed in cultivation"
(3) p.548 "Dieffenbachia are capable of producing seed under commmercial production condition" This study found that the relative humidity limit the seed production. In 100% humidity hand-pollinated pistils have high seed production rate. [seed production restricted to commercial conditions not found in landscape or home environments]

(1) http://www.ars-grin.gov/npgs/cgc_reports/herbscgc1995.htm
(2) Whistler, A.W. (2000) Tropical Ornamentals: A Guide. Timber Press, Inc., Portland, Oregon. 542pp. p.178
(3) Henny, R.J., 1980. Relative humidity affects in vivo pollen germination and seed production in Dieffenbachia maculata 'Perfection'. J. Amer. Soc. Hort. Sci. 105: 546-548.

6.03

Dieffenbachia cultivars is difficult to assess, because the botanical nomenclature of this genus is unclear and due to the existence of many intra- and interspecific hybrids made in the late 1900's.

http://www.ars-grin.gov/npgs/cgc_reports/herbscgc1995.htm

6.04

p.546 "Dieffenbachia maculata 'Perfection' normally has 35-70 pistillate flowers per spadix and 3-5 spadices per plant. Dieffenbachia are dichogamous and inflorescences do not require emasculation before pollination; pistillate flowers are receptive at anthesis while staminate flowers produce pollen 2-3 days later" [Although it is dichogamous, with several spadices in a plant, self pollination is still possile. The plants used in the pollination study are clones and able to produce seeds.]

Henny, R.J., 1980. Relative humidity affects in vivo pollen germination and seed production in Dieffenbachia maculata 'Perfection'. J. Amer. Soc. Hort. Sci. 105: 546-548.

6.05

pollinated by Scarabaeidae beetles [chracteristics of the genus]

http://www.aroid.org/pollination/gibernau/pollinators/index.html

6.06

(1)"propagate by stem cuttings or basal suckers' [spread vegetetatively by yard waste] (2) Bury any inch long piece it will sprout.; leave a small piece laying on the ground when hacking it and it develops roots and grows in no time.

(1)Whistler, A.W. (2000) Tropical Ornamentals: A Guide. Timber Press, Inc., Portland, Oregon. 542pp. p.178 (2)http://davesgarden.com/pdb/go/54969/index.html

6.07

[only known from vegatative propagation]

7.01

"A common houseplant that escapes, probably as a result of discarded plants or cuttings."

http://www.hear.org/pier/species/dieffenbachia_seguine.htm

7.02

"Commercially-grown Dieffenbachia rank among the top ten ornamental tropical foliage plants in terms of wholesale dollar value. They are prized for their attractive variegated foliage and tolerance of interior environments."

http://www.ars-grin.gov/npgs/cgc_reports/herbscgc1995.htm

7.03

no evidence

7.04

"Fruit a globose red-oragnge berry, infrequently formed in cultivation" [bird dispersal syndrome]

Whistler, A.W. (2000) Tropical Ornamentals: A Guide. Timber Press, Inc., Portland, Oregon. 542pp. p.178

7.05

no evidence

7.06

(1)"Fruit a globose red-oragnge berry, infrequently formed in cultivation" [bird dispersal syndrome] (2)"The most popular Dieffenbachia cultivars are propagated asexually either via tissue culture or by tip cuttings. There are no seed propagated varieties." (3)Fruit unknown [not known to produced seeds]

(1)Whistler, A.W. (2000) Tropical Ornamentals: A Guide. Timber Press, Inc., Portland, Oregon. 542pp. p.178 (2)http://www.ars-grin.gov/npgs/cgc_reports/herbscgc1995.htm (3)http://hort.ifas.ufl.edu/shrubs/DIEMACA.PDF

7.07

no evidence

7.08

(1)"Fruit a globose red-oragnge berry, infrequently formed in cultivation" [bird dispersal syndrome] (2)"The most popular Dieffenbachia cultivars are propagated asexually either via tissue culture or by tip cuttings. There are no seed propagated varieties." (3)Fruit unknown [not known to produced seeds]

(1)Whistler, A.W. (2000) Tropical Ornamentals: A Guide. Timber Press, Inc., Portland, Oregon. 542pp. p.178 (2)http://www.ars-grin.gov/npgs/cgc_reports/herbscgc1995.htm (3)http://hort.ifas.ufl.edu/shrubs/DIEMACA.PDF

8.01

(1)p.546 "Dieffenbachia maculata 'Perfection' normally has 35-70 pistillate flowers per spadix and 3-5 spadices per plant."; p.548 "Each pistillate flower from D. maculate 'Perfection' contained 1 ovule per ovary" [Not so many pistillate flowers per plant. Additionally the pollination success is generally poor, which is limited by relative humidity.] (2)Only rhizomes available for sale

(1)Henny, R.J., 1980. Relative humidity affects in vivo pollen germination and seed production in Dieffenbachia maculata 'Perfection'. J. Amer. Soc. Hort. Sci. 105: 546-548. (2)http://www.tropilab.com/dumbcane.html

8.02

no evidence [not known to produce seeds]

8.03

no evidence

8.04

This plant falls over when getting to 6 feet. By cutting off the entire cane it has produced a baby. This is now the third time.; When it gets too tall, just cut the top ; What's left of the old plant will sprout new shoots

http://davesgarden.com/pdb/go/54969/index.html

8.05

The major Dieffenbachia pest is spider mites.

http://www.ars-grin.gov/npgs/cgc_reports/herbscgc1995.htm