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

Rhododendron indicum (L.) Sweet (Azalea indica, Azalea macrantha, evergreen azalea, satsuki, Formosa azalea )

Answer

1.01

Is the species highly domesticated?

y=-3, n=0

1.02

Has the species become naturalized where grown?

y=-1, n=-1

n

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

1

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

y

2.04

Native or naturalized in regions with tropical or subtropical climates

y=1, n=0

n

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

n

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

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

n

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

n

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

y

6.03

Hybridizes naturally

y=1, n=-1

y

6.04

Self-compatible or apomictic

y=1, n=-1

6.05

Requires specialist pollinators

y=-1, n=0

n

6.06

Reproduction by vegetative fragmentation

y=1, n=-1

n

6.07

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

See left

4

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

y

7.05

Propagules water dispersed

y=1, n=-1

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

y

8.02

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

y=1, n=-1

y

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:

4

Notes

Source

1.01

(1) "In fact, the Indian hybrid azaleas are likely the most popular of all flowering evergreen shrubs. They are derived primarily from Sims azalea (R. simsii Planch.) and R. indicum (L.) SweetCwhich, despite its specific epithet, is native to southern Japan not India. These hybrids are confused often with the parent species R. indicum, as they are sometimes sold as varieties or cultivars of R. indicum (LHBH 1976). Indian hybrids are broad mounding shrubs that are 2.5 to 3.0 m tall and usually grow dense in full sunlight and open and airy in the shade. They are utilized in the landscape as accent plants, for screening, and in mass groupings. The large showy flowers are 5 to 9 cm across, blooming in May with colors ranging from white, pink, magenta, and orange-red (Odenwald and Turner 1987). Indian azaleas are grown also as large-flowered greenhouse azaleas." [varieties and cultivars as well as hybrids are selected and grown]
(2) "R. indicum (indica azalea) is one of the oldest Japanese azaleas, bred since anci

(2) http://home.earthlink.net/~gardenphotos/rhodyja.html

1.02

No evidence

1.03

No evidence

2.01

(1)Origin: Hybrids from Japan (2)Native: ASIA-TEMPERATE Eastern Asia: Japan - Honshu, Kyushu

(1)http://www.geocities.com/RainForest/1079/rhodindi.html (2)http://www.ars-grin.gov/cgi-bin/npgs/html/tax_search.pl?Rhododendron+indicum

2.02

2.03

(1) Habitat: Rocks in ravines, C. and S. Japan
(2) Hardiness Range 7A to 10A (3)mountainous areas; marshy areas, freshwater shores

(1) http://www.scs.leeds.ac.uk/cgi-bin/pfaf/arr_html?Rhododendron+indicum&CAN=COMIND
(2) Horticopia A-Z.Horticopia, Inc., Purcellville, VA. ISBN 1-887215-07-7. (3)http://www.jgarden.org/plants.asp?TYPE=SHRUB

2.04

(1) Origin: Hybrids from Japan (2)Native: ASIA-TEMPERATE Eastern Asia: Japan - Honshu, Kyushu

(1)http://www.geocities.com/RainForest/1079/rhodindi.html (2)http://www.ars-grin.gov/cgi-bin/npgs/html/tax_search.pl?Rhododendron+indicum

2.05

(1)Introduced to Florida. (2)Introduced to Hawaii (3)Virginia (4)Widely cultivated in China

(1)http://creatures.ifas.ufl.edu/orn/thrips/gladiolus_thrips.htm (2)http://www.botany.hawaii.edu/faculty/carr/page21.htm (3)Introduced to Virginia (4)http://www.fna.org/china/mss/volume14/Ericaceae-E-Rhododendron_edited.htm

3.01

No evidence

3.02

No evidence

3.03

No evidence

3.04

No evidence

3.05

Rhododendron ponticum is an invader and subject to control in the British Isles

Evans, H. C. Editor: Argent, G. McFarlane, M. (2003) Biological control of invasive alien weeds using fungi, with particular reference to Rhododendron ponticum in the British Isles. Rhododendrons in horticulture and science. Papers presented at the International Rhododendron Conference, Edinburgh, UK on 17-19 May, 2002, 2003, pp. 8-19, many ref.

4.01

No evidence

4.02

No evidence

4.03

No evidence

http://www.omnisterra.com/bot/pp_home.cgi?name=
Rhododendron+indicum&submit=Submit+Query&search=all

4.04

Listed as being resistant to damage by deer.

http://168.29.148.205/www/urbanag/newurbanag/factsheets/deerresistantplants.htm

4.05

'AB: Due to inquiries about the toxicity of ornamental plants to farm data available in the literature on this subject, feeding experiments were performed in cattle with the following plants: Allamanda cathartica, Nerium oleander and Thevetia peruviana of the Apocinaceae family, Codiaeum sp., Euphorbia cotinifolia, Euphorbia pulcherrima and Euphorbia tirucalli of the Euphorbiaceae family, Datura arborea of the Solanaceae family, Colocasia antiquorum, Dieffenbachia picta, Monstera deliciosa, Philodendron bastatum, Philodendron selloum (= P. sellowii) and Scindapsus aureus (= Epipremnum aureum) of the Araceae family, Rhododendron ledifolium and Rhododendron indicum of the Ericaceae family, and Malvaviscus arboreus of the Malvaceae family. The only plants which caused lethal poisoning were Allamanda cathartica, Nerium oleander, Thevetia peruviana and Rhododendron indicum. The lethal dose for A. cathartica was 30 g/kg (causing death of 2 of 3 bovines which received this dose), for N. oleander it varied from 0,25

TI: Experiments on the toxicity of some ornamental plants in cattle AU: Tokarnia,-Carlos-Hubinger [Reprint-author]; rmien,-Anibal-Guillemo [Author]; Peixoto,-Paul-Vargas [Author]; Barbosa,-Jose-Diomedes [Author]; Brito,-Marilene-De-Farias [Author]; Dobereiner,-Jurgen [Author] SO: Pesquisa- eterinaria-Brasileira. 1996; 16(1): 5-20.

4.06

The work reports the first occurrence of Caloptilia azaleella (Brants, 1913) (Lepidoptera: Gracillaridae) in Brazil. The pest was found in Rhododendron indicum (L.) Sweet (Ericaceae) plants, in yellow and white varieties in São Paulo (SP), Joinville (SC) and Ubatuba (SP) cities. Biological aspects were observed in the laboratory and damage is described.
[Caloptilia azaleella is a recognized specialist pest attacking many ornamental Rhododendron species]

Rodrigues Netto, S. M. Bergmann, E. C. Imenes, S. D. L. (1994) Occurrence of Caloptilia azaleella (Brants, 1913) in Rhododendron indicum (L.) Sweet. (Foreign Title: Ocorrência de Caloptilia azaleella (Brants, 1913) em Rhododendron indicum (L.) Sweet.) Arquivos do Instituto Biológico (São Paulo), 1994, Vol. 61, No. 1/2, pp. 57-59, 14 ref.

4.07

(1) 'Although no specific mention of toxicity has been seen for this species, it belongs to a genus where many members have poisonous leaves. The pollen of many if not all species of rhododendrons is also probably toxic, being said to cause intoxication when eaten in large quantities.' (2)Mode: Ingestion. Poisonous Part: All parts. Symptoms: Salivation, watering of eyes and nose, abdominal pain, loss of energy, depression, nausea and vomiting, diarrhea, weakness, difficult breathing, progressive paralysis of arms and legs, coma.
Toxic Principle: Andromedotoxin. Severity: HIGHLY TOXIC, MAY BE FATAL IF EATEN!
(3) "This plant is considered mostly allergy free and causes little or no allergy problems in most people. Foliage from most members of this genus is considered poisonous when ingested." [no evidence of human poisonings]

(1)http://www.scs.leeds.ac.uk/cgi-bin/pfaf/arr_html?Rhododendron+indicum&CAN=COMIND (2)http://www.ces.ncsu.edu/depts/hort/consumer/poison/Rhodosp.htm
(3) Horticopia A-Z.Horticopia, Inc., Purcellville, VA. ISBN 1-887215-07-7.

4.08

Habit: Evergreen [moist habitats]

http://www.ces.ncsu.edu/depts/hort/consumer/factsheets/shrubs/rhododendron_indicum.html

4.09

(1)Exposure: Shade or part shade (2)prefers partial shade or partial sun (3)Sun Exposure: Full Sun (4) It can grow in semi-shade (light woodland).

(1)http://www.geocities.com/RainForest/1079/rhodindi.html (2)http://www.horticopia.com/hortpix/html/pc4624.htm (3)http://plantsdatabase.com/go/56169/ (4)http://www.scs.leeds.ac.uk/cgi-bin/pfaf/arr_html?Rhododendron+indicum&CAN=COMIND

4.1

(1)The plant prefers light (sandy) and medium (loamy) soils and requires well-drained soil. The plant prefers acid soils and can grow in very acid soil. (2)well-drained acidic soil enriched with organic matter
(3) Soil Condition: Loamy, sandy, clay, acidic, neutral, salt intolerant, somewhat drought tolerant (4)Succeeds in a most humus-rich lime-free soils; Prefers a peaty or well-drained sandy loam; This plant variety does not tolerate heavy clay soils.

(1)http://www.scs.leeds.ac.uk/cgi-bin/pfaf/arr_html?Rhododendron+indicum&CAN=COMIND (2)http://www.ces.ncsu.edu/depts/hort/consumer/factsheets/shrubs/rhododendron_indicum.html
(3) Horticopia A-Z.Horticopia, Inc., Purcellville, VA. ISBN 1-887215-07-7. (4)http://plants.gardenbed.com/56/5565_cul.asp

4.11

Not a climber - a shrub.

http://plantsdatabase.com/go/56169/

4.12

No evidence

5.01

Ericaceae

5.02

Perennial shrub - 6-8 ft. (1.8-2.4 m)

http://plantsdatabase.com/go/56169/

5.03

No evidence

5.04

Ericaceae

6.01

No evidence

6.02

(1)Seed - best sown in a greenhouse as soon as it is ripe in the autumn and given artificial light. Alternatively sow the seed in a lightly shaded part of the warm greenhouse in late winter or in a cold greenhouse in April. Surface-sow the seed and do not allow the compost to become dry[200]. Pot up the seedlings when they are large enough to handle and grow on in a greenhouse for at least the first winter. (2)Preferred temperature for germination : 65-70 degrees F
Time required for germination : 2-4 weeks

(1)http://www.scs.leeds.ac.uk/cgi-bin/pfaf/arr_html?Rhododendron+indicum&CAN=COMIND (2)http://hort.ifas.ufl.edu/lppi/htm/sp325.htm

6.03

"R. eriocarpum Tsutsusi (Azalea): Shrubs to 3 ft. Flowers (July) are red to purple, rose, pink or white. Natural hybrids of this species and R. indicum, which grow together on Yaku Island, are considered the first of the Satsuki Hybrids. "

http://www.rhododendron.dk/rsf_dj.htm

6.04

mentions that self-pollination occurs in the genus [but hybrid cultivated varieties may be sterile]

http://www.mdrhododendron.org/faq.html

6.05

(1)The flowers are hermaphrodite (have both male and female organs) and are pollinated by Insects. (2)This plant is attractive to bees, butterflies and/or birds

(1)http://plantsdatabase.com/go/56169/ (2)http://www.scs.leeds.ac.uk/cgi-bin/pfaf/arr_html?Rhododendron+indicum&CAN=COMIND

6.06

No evidence

6.07

(1)Rhododendron yakushimanum [fastest] may bloom in only 2-3 years, slower ones may take up to 7 years. (2)Growth Rate: Moderate [minimum estimate for a moderate growth rate Rhododendron]

(1)http://www.mdrhododendron.org/faq.html (20http://www.skinnernurseries.com/azalea.htm

7.01

minute seeds may stick to mud on shoes; grow widely in gardens

7.02

Evergreen azaleas are the most popular broad-leafed evergreen and third most popular flowering pot plant in the United States based on data from the 1998 Census of Horticultural Specialties (www.nass.usda.gov). Production of azaleas accounts for 30 to 40 % of container nursery production in USDA Cold Hardiness Zone 8 in Mississippi, Alabama and Louisiana....

http://216.239.57.104/search?q=cache:5eVHd_82jSsJ:
www.msstate.edu/dept/crec/ornamental%2520horticulture
%2520genetics.pdf+Rhododendron+indicum+incompatibility&hl=en

7.03

No products

http://victoria.tc.ca/Recreation/RhodoSoc/Archives/Harv202.htm

7.04

(1)"Fruits are oblong, 5-valved, dehiscent capsules that generally ripen during autumn. When mature, capsules turn from green to brown, at which time they split along the sides, releasing minute seeds. Capsules of rosebay rhododendron contain about 400 viable seeds/capsule" [characters of the genus, very small seeds] (2)Seeds vary numerous, minute, fusiform, always winged, or both ends with appendages or thready tails.[clear adaptations for wind]

(1)http://wpsm.net/Rhododendron.pdf (2)http://www.fna.org/china/mss/volume14/Ericaceae-E-Rhododendron_edited.htm

7.05

grows in wet habitats [seeds may float]

7.06

"Fruits are oblong, 5-valved, dehiscent capsules that generally ripen during autumn (figure 1). When mature, capsules turn from green to brown, at which time they split along the sides, releasing minute seeds (figures 2B4). Capsules of rosebay rhododendron contain about 400 viable seeds/capsule (Romancier 1970)." [characters of the genus]

http://wpsm.net/Rhododendron.pdf

7.07

No evidence

7.08

No evidence of being ingested

8.01

[Genus characteristic]The seed ecology of rhododendrons is that they produce very large numbers of very small seeds.

http://victoria.tc.ca/Recreation/RhodoSoc/Archives/Harv202.htm

8.02

"Seeds of rhododendrons with a moisture content of 4 to 9% will remain viable about 2 years at room temperature (Bowers 1960; Olson 1974). However, at room temperature, seeds lose their viability at a rate of 50% a year, and those that retain their ability to germinate will sprout more slowly (Leach 1961)." [a large portion of dried seeds remain viable after one year and show some degree of dormancy]

http://wpsm.net/Rhododendron.pdf

8.03

No evidence that the species is being controlled for.

8.04

(1) Prune: Shear after bloom; do not prune after August
(2) "Do not cultivate around it, since it has surface roots and do not let the soil cover the stem. The shallow root systems are easily injured by deep cultivation but benefit from mulching." [easily damaged]

(1) http://www.geocities.com/RainForest/1079/rhodindi.html
(2) Horticopia A-Z.Horticopia, Inc., Purcellville, VA. ISBN 1-887215-07-7.

8.05

Don t know