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

Euphorbia milii Des Moul.; Euphorbia splendens (crown of thorns)

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

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

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

n

3.04

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

n=0

n

3.05

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

n=0

y

4.01

Produces spines, thorns or burrs

y=1, n=0

y

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

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

4.09

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

y=1, n=0

n

4.1

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

y=1, n=0

n

4.11

Climbing or smothering growth habit

y=1, n=0

n

4.12

Forms dense thickets

y=1, n=0

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

y

6.03

Hybridizes naturally

y=1, n=-1

6.04

Self-compatible or apomictic

y=1, n=-1

n

6.05

Requires specialist pollinators

y=-1, n=0

n

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

1

7.01

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

y=1, n=-1

n

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

8.03

Well controlled by herbicides

y=-1, n=1

8.04

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

y=1, n=-1

n

8.05

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

y=-1, n=1

Total score:

1

Notes

Source

1.01

(1)The Crown-of-Thorns is a Madagascar native shrub thatcan reach a height of 5 feet with an equal spread (Fig. 1).Cultivars have been selected and made available with matureheights ranging from 1 to 5 feet. The prostrate cultivars growin a spreading fashion and can be used as a ground cover. (2)A number of varieties and forms of this species are recognised (Jacobsen 1974), the two most commonly encountered being E. milii var milii (syns E. milii Des Moul., E. bojeri Hooker) and E. milii var splendens Ursch & Leandri (syn. E. splendens Bojer). Both of these varieties are commonly found in collections of succulent plants. (3)There are many cvs of E. milii, mostly of hybridorigin, produced either naturally or throughcontrolled crosses, & designated E. x lomi. These maybe divided into 2 broad groups: the more common, oldertypes; & the recently developed Thai hybrid

(1)http://66.102.7.104/search?q=cache:y4mgU9XUFA4J:hort.ifas.ufl.edu/shrubs/EUPMILA.PDF+Euphorbia+milii&hl=en (2)http://bodd.cf.ac.uk/BotDermFolder/BotDermE/EUPH.html (3)http://216.239.53.104/search?q=cache:uzCRSRtIRnYJ:miami-dade.ifas.ufl.edu/programs/commorn/publications/crown-of-thorns-production.PDF+Euphorbia+milii+seeds&hl=en

1.02

(1)Naturalized in other tropical countries and largely used like house plant, decorative tropical, even in the form of particularly impenetrable low hedge. [vague, not listed in tropical floras] (2)Cultivated and escaped in Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Yunnan, Zhejiang [China, "escape" around plantings] (3)Rare escape from cultivation, Sarasota County FL

(1)http://translate.google.com/translate?hl=en&sl=fr&u=
http://www.cactuspro.com/encyclo_espece.php%3Faction%3Dafficher%26fiche_id
%3D276&prev=/search%3Fq%3DEuphorbia%2Bmilii%26start%3D10%26hl%3
Den%26lr%3D%26ie%3DUTF-8%26sa%3DN (2)http://www.fna.org/china/mss/volume11/
Euphorbiaceae-MO-Euphorbia_coauthoring.htm (3)Wunderlin, R.P. 1998. Guide to the vascular plants of Florida. University Press of Florida. Gainesville.

1.03

No evidence

2.01

Origin: Madagascar

http://www.desert-tropicals.com/Plants/Euphorbiaceae/Euphorbia_milii.html

2.02

2.03

(1)USDA: 9b to 10 depending on the variety (2)USDA zones: 9a to 11 (3)Does not tolerate wet conditions

(1)http://www.desert-tropicals.com/Plants/Euphorbiaceae/Euphorbia_milii.html (2)http://plantsdatabase.com/go/1925/ (3)http://hort.ifas.ufl.edu/shrubs/EUPMILA.PDF

2.04

Naturalized in other tropical countries and largely used like house plant, decorative tropical, even in the form of particularly impenetrable low hedge.

http://translate.google.com/translate?hl=en&sl=fr&u=
http://www.cactuspro.com/encyclo_espece.php%3Faction%3Dafficher%26fiche_id
%3D276&prev=/search%3Fq%3DEuphorbia%2Bmilii
%26start%3D10%26hl%3Den%26lr%3D%26ie%3DUTF-8%26sa%3DN

2.05

(1)The"Crown of Thorns" is one of the popular ornamental plants in Thailand, Taiwan and in Indonesia. (2)The plant is grown as a garden subject in western Australia.

(1)http://www.indoflorist.com/euphorbia.html (2)http://bodd.cf.ac.uk/BotDermFolder/BotDermE/EUPH.html

3.01

(1)Naturalized in other tropical countries and largely used like house plant, decorative tropical, even in the form of particularly impenetrable low hedge. [vague, not listed in tropical floras] (2)Cultivated and escaped in Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Yunnan, Zhejiang [China, "escape" around plantings] (3)Rare escape from cultivation, Sarasota County FL

(1)http://translate.google.com/translate?hl=en&sl=fr&u=
http://www.cactuspro.com/encyclo_espece.php%3Faction%3Dafficher%26fiche_id%3
D276&prev=/search%3Fq%3DEuphorbia%2Bmilii%26start%3D10%26hl%3Den%
26lr%3D%26ie%3DUTF-8%26sa%3DN (2)http://www.fna.org/china/mss/volume11/
Euphorbiaceae-MO-Euphorbia_coauthoring.htm (3)Wunderlin, R.P. 1998. Guide to the vascular plants of Florida. University Press of Florida. Gainesville.

3.02

No evidence

3.03

No evidence

3.04

Invasive potential: not known to be invasive

http://66.102.7.104/search?q=cache:y4mgU9XUFA4J:hort.ifas.ufl.edu/shrubs/EUPMILA.PDF+Euphorbia+milii&hl=en

3.05

E. helioscopia, E. heterophylla and E. hirta are listed as principal weeds in several countries.

Holm et al. 1997. An electronic atlas of weeds and invasive species. Version 1. CD-ROM database.

4.01

The leaves that are present on this plant are restricted to the newgrowth, and they fall off quickly to reveal a stem with 1-inch-long straight thorns.

http://66.102.7.104/search?q=cache:y4mgU9XUFA4J:hort.ifas.ufl.edu/shrubs/EUPMILA.PDF+Euphorbia+milii&hl=en

4.02

No evidence

4.03

No evidence

4.04

(1)thorns. (2)The poisonous principle is present in all parts of the plant. Euphorbia species generally are highly unpalatable, but animals may eat them due to lack of good forage. Drying does not destroy the toxicity of the plant, and Euphorbia in hay may be slightly more palatable to livestock. Contact with the white, milky sap may cause severe blistering as well as intense pain to open cuts or eyes.

(1)http://66.102.7.104/search?q=cache:y4mgU9XUFA4J:hort.ifas.ufl.edu/shrubs/EUPMILA.PDF+Euphorbia+milii&hl=en (2)http://gateway.library.uiuc.edu/vex/toxic/crown/crown2.htm

4.05

'Generally horses, cattle, sheep, cats, dogs and humans are affected by Euphorbia and may experience severe irritation of the mouth and gastrointestinal tract, sometimes with hemorrhage and diarrhea. Other general signs include blistering, swelling about the eyes and mouth, excessive salivation and emesis, abdominal pain and weakness. The sap may cause dermatitis. Death is rare. Work horses may suffer severe blisters and loss of hair on the ankles. Approximately 3 kg of E. prostrata and E. marginata when fed to cattle produces severe scours and emaciation.' [no evidence of poisoning by E. milii which is unlikely to be eaten in the first place because of abundant spines - unpalatable]

http://gateway.library.uiuc.edu/vex/toxic/crown/crown5.htm

4.06

This site lists 15 fungi species to be associated with E. milli.
(2) Amphobotrys ricini is a specialist pathogen causing blight on ornamental Euphorbia species.
(3) "It is recommended that control measures should include poinsettia [Euphorbia pulcherrima] and E. milii, which are also susceptible." [Xanthomonas campestris pv. poinsettiicola is a recognized specialist pathogen subjected to control efforts]

http://nt.ars-grin.gov/fungaldatabases/all/FindRecOneFungusFrame.cfm
Sanoamuang, N. (1996) First report of gray mold blight caused by Amphobotrys ricini on crown of thorns in Thailand.
(2) Plant Disease, 1996, Vol. 80, No. 2, pp. 223, 2 ref. ; Holcomb, G.E., and Brown, W.L. 1990. Basal stem rot of cultivated poinsettia caused by Amphobotrys ricini. Pl. Dis. 74:828; Miller, J.W. 1991. Bureau of Plant Pathology. Tri-ology Techn. Rep. Div. Pl. Indust., Florida 30(8):1-2
(3) Chase, A. R. (1985) Bacterial leaf spot of Codiaeum variegatum cultivars caused by Xanthomonas campestris pv. poinsettiicola. Plant Pathology, 1985, Vol. 34, No. 3, pp. 446-448, 5 ref.

4.07

(1)As with the other Euphorbias, its sap is poisonous, it irritates the skin, and can cause temporary blindness if it goes in the eyes. (2)Poisonous Part All parts. Symptoms Nausea, vomiting, diarrhea when ingested. Redness, swelling, blisters after some delay following contact with skin. Toxic Principle Diterpene esters in milky latex. Severity CAUSES ONLY LOW TOXICITY IF EATEN. SKIN IRRITATION MINOR, OR LASTING ONLY FOR A FEW MINUTES. CAUSES ONLY LOW TOXICITY IF EATEN. SKIN IRRITATION MINOR, OR LASTING ONLY FOR A FEW MINUTES. (3)Generally horses, cattle, sheep, cats, dogs and humans are affected by Euphorbia and may experience severe irritation of the mouth and gastrointestinal tract, sometimes with hemorrhage and diarrhea. Other general signs include blistering, swelling about the eyes and mouth, excessive salivation and emesis, abdominal pain and weakness. The sap may cause dermatitis. Death is rare. Work horses may suffer severe blisters and loss of hair on the ankles. Approximately 3 kg of E. prostrat

(1)http://www.desert-tropicals.com/Plants/Euphorbiaceae/Euphorbia_milii.html (2)http://www.ces.ncsu.edu/depts/hort/consumer/poison/Euphomi.htm (3)http://gateway.library.uiuc.edu/vex/toxic/crown/crown5.htm (4)http://members.rogers.com/mulligan4520/poison/

4.08

Leaf type and persistence: deciduous [leaves on new growth only; dryland shrub - might be fire hazard]

http://hort.ifas.ufl.edu/shrubs/EUPMILA.PDF

4.09

(1)Sun Exposure: Full sun to light shade (light shade better in Phoenix) (2)Light requirement: plant grows in full sun

(1)http://www.desert-tropicals.com/Plants/Euphorbiaceae/Euphorbia_milii.html (2)Light requirement: plant grows in full sun

4.1

Soil tolerances: acidic; alkaline; sand; loam, Well-drained soils are essential to successfully grow this plant.

http://66.102.7.104/search?q=cache:y4mgU9XUFA4J:hort.ifas.ufl.edu/shrubs/EUPMILA.PDF+Euphorbia+milii&hl=en

4.11

Not a climber - an evergreen shrub.

http://gateway.library.uiuc.edu/vex/toxic/crown/crown0.htm

4.12

Grows as "impenetrable low hedge" [up to 5 feet tall but no evidence whether they are naturally abundant enough to form a thicket ]

http://translate.google.com/translate?hl=en&sl=fr&u=
http://www.cactuspro.com/encyclo_espece.php%3Faction%3Dafficher%26fiche_id%3D276&
prev=/search%3Fq%3DEuphorbia%2Bmilii%26start%3D10%26hl%3Den%26lr%3D%26ie%3DUTF-8%26sa%3DN

5.01

Terrestrial

http://www.desert-tropicals.com/Plants/Euphorbiaceae/Euphorbia_milii.html

5.02

Woody perennial to 4 feet (1.2 m)

http://www.desert-tropicals.com/Plants/Euphorbiaceae/Euphorbia_milii.html

5.03

Euphorbiaceae

5.04

No evidence

6.01

Natural crosses similar in appearance, but withthicker leaves and thinner stems, were collected in thewild in Madagascar, then propagated commercially inGermany. This group includes varieties like‘Somona’ & ‘Gabriella’, & the formal name E. x lomiHeidelberg Group has been proposed for this group of hybrids. Many of these & other E. milii varieties areavailable from specialist growers

http://216.239.53.104/search?q=cache:uzCRSRtIRnYJ:miami-dade.ifas.ufl.edu/programs/commorn/publications/crown-of-thorns-production.PDF+Euphorbia+milii+seeds&hl=en

6.02

Seeds can be used to propagate E. milii, butare mainly used for developing new cvs. In Floridaplants rarely produce fruit (a three lobed schizocarp)without help from man.

http://216.239.53.104/search?q=cache:uzCRSRtIRnYJ:miami-dade.ifas.ufl.edu/programs/commorn/publications/crown-of-thorns-production.PDF+Euphorbia+milii+seeds&hl=en

6.03

Natural crosses similar in appearance, but with thicker leaves and thinner stems, were collected in thewild in Madagascar, then propagated commercially inGermany. This group includes varieties like‘Somona’ & ‘Gabriella’, & the formal name E. x lomiHeidelberg Group has been proposed for this group of hybrids. Many of these & other E. milii varieties areavailable from specialist growers [intraspecific hybrids]

http://216.239.53.104/search?q=cache:uzCRSRtIRnYJ:miami-dade.ifas.ufl.edu/programs/commorn/publications/crown-of-thorns-production.PDF+Euphorbia+milii+seeds&hl=en

6.04

Pollen release & receptivityof the stigma usually do not coincide for a single plant, which in nature encourages out-crossing. So you need 2 or more plants, preferably of different cvs

http://216.239.53.104/search?q=cache:uzCRSRtIRnYJ:miami-dade.ifas.ufl.edu/programs/commorn/publications/crown-of-thorns-production.PDF+Euphorbia+milii+seeds&hl=en

6.05

These are common ornamental plants, moderately visited by A. mellifera and sometimes also by mandacaia (Melipona quadrifasciata) and urucu amarela (M. rufiventris).

http://66.102.7.104/search?q=cache:NymLYs-yt98J:eco.ib.usp.br/beelab/livro_01_nogueira_neto.pdf+Euphorbia+milii+pollinators&hl=en

6.06

Propagation: Stem cuttings, seeds

http://www.desert-tropicals.com/Plants/Euphorbiaceae/Euphorbia_milii.html

6.07

(1)Seedlings will bloom in 5-8 months (2)Growth rate: slow

(1)http://216.239.53.104/search?q=cache:uzCRSRtIRnYJ:miami-dade.ifas.ufl.edu/programs/commorn/publications/crown-of-thorns-production.PDF+Euphorbia+milii+seeds&hl=en (2)http://hort.ifas.ufl.edu/shrubs/EUPMILA.PDF

7.01

No evidence that the propagules have any means of attachment.

7.02

Uses: ground cover; edging; mass planting; cascading down awall

http://66.102.7.104/search?q=cache:y4mgU9XUFA4J:hort.ifas.ufl.edu/shrubs/EUPMILA.PDF+Euphorbia+milii&hl=en

7.03

'Seeds can be used to propagate E. milii, but are mainly used for developing new cvs. In Floridaplants rarely produce fruit (a three lobed schizocarp)without help from man.'

http://216.239.53.104/search?q=cache:uzCRSRtIRnYJ:miami-dade.ifas.ufl.edu/programs/commorn/publications/crown-of-thorns-production.PDF+Euphorbia+milii+seeds&hl=en

7.04

FRUITS: Dry, breaking into 3, 1-seeded segments no adaptations for wind]

http://www.allergenica.com/Details.asp?PLANTID=62

7.05

No evidence [dry environments]

7.06

FRUITS: Dry, breaking into 3, 1-seeded segments

http://www.allergenica.com/Details.asp?PLANTID=62

7.07

No evidence of the propagules having any means of attachment

7.08

No evidence that the fruits are ingested.

8.01

(1)The fruits are small capsules that are rarely formed in Florida. (2)Fruit infrequently formed in cultivation

(1)http://66.102.7.104/search?q=cache:y4mgU9XUFA4J:hort.ifas.ufl.edu/shrubs/EUPMILA.PDF+Euphorbia+milii&hl=en (2)Whistler, W.A. 2000. Tropical Ornamentals. Timber press. Portland.

8.02

No evidence regarding seedbank.

8.03

No evidence that the species is being controlled for.

8.04

(1)Since crown-of-thorns is not fast growing, pruning isusually not necessary until the second or third year ofgrowth. Pruning is best done during cool, dryweather to lessen the risk of stem disease. With thespecies lightly prune, removing only dead & overlytangled stems. Perform a major pruning every 2-3years in late Spring. For the compact varieties, thinout at the base to permit adequate air circulation (2)[Pruning not recommended during stress]

(1)http://216.239.53.104/search?q=cache:uzCRSRtIRnYJ:miami-dade.ifas.ufl.edu/programs/commorn/publications/crown-of-thorns-production.PDF+Euphorbia+milii+seeds&hl=en (2)http://www.ext.nodak.edu/extnews/hortiscope/shrub/crwnthrns.htm

8.05

Don’t know