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

Lagerstroemia indica L. X L. fauriei, crepe myrtle hybrid; Hybrid Crape Myrtlette

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

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

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

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

n

4.06

Host for recognized pests and pathogens

y=1, n=0

n

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

n

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

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

6.05

Requires specialist pollinators

y=-1, n=0

n

6.06

Reproduction by vegetative fragmentation

y=1, n=-1

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

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

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

y

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:

4

Notes

Source

1.01

cultivated hybrids produced by the US National Arboretum within the past 50 years, but not selected over several generations for modified traits

Title: Molecular genetic diversity among 12 clones of Lagerstroemia fauriei revealed by AFLP and RAPD markers.
Author(s): Pooler, Margaret R.
Source: Hortscience 38 (2) : 256-259 April 2003
Abstract: Many popular crapemyrtle (Lagerstroemia L.) cultivars grown in the United States are interspecific hybrids between L. indica L. and L. fauriei Koehne. The 22 hybrid cultivars released from the U.S. National Arboretum contain primarily genetic material from L. fauriei PI 237884. Examining the genetic diversity of L. fauriei specimens in the U.S. is valuable because of the historical and economic significance of the species, the increasing interest it is receiving as a source of new cultivars, and its threatened status in the wild. Our objectives were to examine molecular genetic diversity among L. fauriei accessions using Randomly Amplified Polymorphic DNA (RAPD) and Amplified Fragment Length Polymorphisms (AFLP) markers. Our results indicate: 1) RAPD and AFLP markers are generally consistent in the genetic relat

1.02

Originally from Asia, crape myrtle has been naturalized throughout the United States as far north as Massachusetts [refers to L. indica]

http://www.floridata.com/ref/l/lager_i.cfm

1.03

no evidence

2.01

(1) Hardiness: USDA Zone 6-9b (2) Hardiness: Reliably top hardy to U.S.D.A. Zone 7b; root hardy to U.S.D.A. Zones 6

(1) http://davesgarden.com/pf/go/918/ (2) http://www.usna.usda.gov/Newintro/chicksaw.html

2.02

2.03

(1) Hardiness: USDA Zone 6-9b (2) Hardiness: Reliably top hardy to U.S.D.A. Zone 7b; root hardy to U.S.D.A. Zones 6

(1) http://davesgarden.com/pf/go/918/ (2) http://www.usna.usda.gov/Newintro/chicksaw.html

2.04

no evidence

2.05

[hundreds of hybrid cultivars popular around the world]

http://www.cshs.ca/annual_meeting/scientific_2002/Symposium_S18.pdf

3.01

Originally from Asia, crape myrtle has been naturalized throughout the United States as far north as Massachusetts [refers to L. indica]

http://www.floridata.com/ref/l/lager_i.cfm

3.02

no evidence

3.03

no evidence

3.04

no evidence

3.05

L. indica is described as "setting seed in the Staff Village" [no evidence that it has actually caused environmental problems]

http://www.sanparks.org/parks/kruger/conservation/scientific/ff/alien_biota/layout.pdf

4.01

no description of these traits

http://www.usna.usda.gov/Newintro/chicksaw.html

4.02

No

http://plants.usda.gov/cgi_bin/plant_attribute.cgi?symbol=LAIN

4.03

no evidence

4.04

Low palatability for browsing and grazing animals. [Lagerstroemia indica ]

http://plants.usda.gov/cgi_bin/plant_attribute.cgi?symbol=LAIN

4.05

no evidence

4.06

Erysiphe lagerstroemiae (powdery mildew) is a specialist pathogen to Lagerstroemia spp. [this is a pest of the parental species]

Caddo' and 'Tonto' Lagerstroemia. By: Egolf, D. R.; HortScience 25 (5), 1990, p.585-587

4.07

no evidence

4.08

Low flammability, deciduous, no other evidence suggests creating a fire hazard

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

4.09

(1)Sun Exposure: Full Sun to Partial Shade (2)Full sun is necessary for best flowering and for development of a full, symmetrical crown.

(1)http://davesgarden.com/pf/go/918/ (2)http://edis.ifas.ufl.edu/scripts/htmlgen.exe?DOCUMENT_MG266

4.1

They will grow on a wide variety of soils, although all grow best in well-drained, organic soils that receive fortnightly summer irrigation.

http://www.metrotrees.com.au/treehandbook/page-listings/lagerstroemia-hybrids.html

4.11

tree

http://www.metrotrees.com.au/treehandbook/page-listings/lagerstroemia-hybrids.html

4.12

no evidence

5.01

terrestrial

5.02

tree; Lythraceae

5.03

no evidence

5.04

tree

6.01

no evidence

6.02

Propagation Methods:
From semi-hardwood cuttings
From hardwood heel cuttings
From seed; sow indoors before last frost [This refers to L. indica, but don't know about fertility of hybrids]

http://davesgarden.com/pf/go/918/

6.03

no evidence

6.04

In both L. indica (an ornamental shrub) and L. parviflora (a tree used for timber), pollen tube growth was studied following self and cross pollinations. Tubes grew normally for the entire length of the style in cross pollinated flowers of both species, but in selfed flowers they reached only the middle part of the style before their tips swelled and they ceased to grow. The inhibition of pollen tubes in the style suggested that a gametophytic self incompatibility system acts in both species. [Parent is self-incompatible but don't know about hybrid]

6.05

This plant is attractive to bees, butterflies and/or birds

http://davesgarden.com/pf/go/918/

6.06

Some trees sprout from the base of the trunk and roots [common root suckers allow spread by vegetative fragmentation, but this refers to L. indica and root suckers in hybrids are not known]

http://edis.ifas.ufl.edu/ST342

6.07

(1)"In a warm greenhouse, such seedlings will make rapid growth, and often bloom the first summer from a December or January sowing." (2)Plants grown from seed sown in the winter will bloom by mid-summer, making this a good annual for colder regions, or a very dwarf shrub in warmer regions.

(1)http://wpsm.net/Lagerstromia.pdf (2)http://davesgarden.com/pf/go/918/

7.01

[a roadside tree producing many tiny, wind dispersed seeds that will follow vehicles]
(1) "The following species are proposed as the main roadside trees: Lagerstroemia indica, Choerospondias axillaris, Cercis chinensis, Sassafras tzumu, Livistona chinensis, Bischofia javanica, Photinia serrulata, Machilus thunbergii [Persea thunbergii ], Casuarina equisetifolia ." (2) "fruit maturing in fall, a round woody capsule splitting and liberating tiny winged seeds"

(1) Hang, JinSheng; Lin, LiHua; Chen, Ce; Shao, QingSong (2003) Current situation and tentative distribution idea of road side tree in Wenzhou City. Journal of Zhejiang Forestry Science and Technology, 2003, Vol.23, No.2, pp.76-79, 7 ref.
(2) http://www.ces.ncsu.edu/depts/hort/consumer/factsheets/maritime/Lagerin.htm

7.02

Over the last 20 years, new Crepemyrtle selections have been introduced from the United States National Arboretum that have all of the excellent qualities of L. indica, and are also highly resistant to Powdery Mildew. These hybrids were bred by Dr. D. Egolf, and have proven themselves as excellent urban trees.

http://www.metrotrees.com.au/treehandbook/page-listings/lagerstroemia-hybrids.html

7.03

no evidence

7.04

The red-brown fruit is a capsule containing flattened seeds which are wind-dispersed.

http://www.up.ac.za/academic/botany/garden/species/101.html

7.05

no evidence

7.06

Fruit: Capsular fruits

http://www.canopy.org/db/main.asp?tree=36

7.07

no evidence

7.08

no evidence

8.01

(1) "Viable seeds/kg : 50000 - 100000"
(2) "Each capsule contains 20 or more winged seeds. Seeds are 7 to 11 mm long"; "Spectacular flowering is the trait that most often justifies use of crape-myrtles as landscape plants. The red, white, pink, or purple flowers, each 1.5 to 5.0 cm in diameter, are produced in 12- to 44-cm-long tapered panicles, each comprising 25 to 500 flowers."
[need less than 50 fruits per square meter, which could be attained by a single flowering branche]

(1) http://www.worldagroforestrycentre.org/Sites/TreeDBS/TSSD/seedinfo.cfm?seed_id=lagind
(2) http://wpsm.net/Lagerstromia.pdf

8.02

no evidence of dormancy "Egolf and Andrick (1978) reported that without stratification, seeds sown at 15 degree C germinated within 10 days."

http://wpsm.net/Lagerstromia.pdf

8.03

Basagran (bentazon) application caused foliar injury on Crape Myrtle [susceptible to herbicide that is meant to be specific to nutsedges (Cyperaceae)]

http://www.clemson.edu/hort/sctop/csec/csec-04.htm

8.04

"In the St. Louis area (Zone 5b to 6a), it is probably best to grow these plants as perennials (like buddleias) by cutting all stems back to several inches in early spring. Roots will sprout new stems and flowers will appear on the new growth." (2)Ability to resprout.

http://www.mobot.org/gardeninghelp/plantfinder/Plant.asp?code=W100 (2)http://plants.usda.gov/cgi_bin/plant_attribute.cgi?symbol=LAIN

8.05

no evidence