Fraxinus uhdei (Wenzig) Lingelsh., Oleaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  yes

Risk assessment results:  High risk, score: 11 (Go to the risk assessment)

Common name(s): [more details]

English: Mexican ash, shamel ash, tropical ash

Spanish: fresno

Habit:  tree

Description:  "Trees up to 24 (-28) m tall, bark gray or brown, furrowed; young branches pubescent, soon glabrate. Leaves 15-28 cm long, leaflets 5-9, (5-) 7-11 cm long, 2-5 cm wide, upper surface dull green, glabrous, lower surface pale green, puberulent along midrib, margins irregularly serrulate, apex long-acuminate, base cuneate, petioles 6-10 cm long, petiolules 3-13 mm long. Flowers unisexual (and the plants dioecious), in panicles 13-20 cm long; buds paired, covered with brown, finely pubescent scales; calyx minute, 4-toothed. Samaras oblong-elliptic to oblong-oblanceolate, 2-4 cm long, the wing 5-6 mm wide, apex with a small notch" (Wagner et al., 1999; p. 991).

Habitat/ecology:  "Forests and forest edges.  A native of alluvial soils, growing along streams.  Where invasive, it colonizes disturbed areas in forests and precludes the establishment of native plants.  The large canopies shade out most understory species and prevent forest succession"  (Weber, 2003; p. 174).

In Hawai‘i, it grows best between 1,000 and 1,750 m but also grows up to 2,000 m. Shade tolerant, prolific seed producer.

Propagation:  "Fruits are dispersed by wind and water.  Seeds may remain viable in the soil for 6 years or longer.  The tree regenerates vigorously from root and shoot sprouts"  (Weber, 2003; p. 174).

Native range:  Central and southern Mexico, Costa Rica; Guatemala, Honduras; also cultivated (GRIN).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Ecuador (Galápagos Islands) San Cristóbal Group	San Cristóbal Island	introduced cultivated	Charles Darwin Foundation (2008)
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 991)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 991)
State of Hawaii Hawaiian Islands	Lāna‘i Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 991)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 991)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 991)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 991)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Central America Central America (Pacific rim)	Costa Rica (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Guatemala (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Honduras (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Mexico Mexico	Mexico (United Mexican States)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)

Comments:  Extensively planted as a forestry tree in Hawai‘i with extensive reseeding within and naturalization outside the planted stands (Wagner et al., 1999; p. 991)

Control:  Additional control information from the Bugwood Wiki.

Chemical:  "In trials at Kamakou Preserve, Moloka‘i, tropical ash was susceptible to cut-surface (continuous ring) applications of 2,4-D, dicamba, glyphosate and picloram, each of which caused complete control. Applied in 2 notches per trunk, these same herbicides, except for picloram, caused severe injury. It took 18 months for trees to die. In comparisons of applications to 4 drilled holes per tree and continuous ring notching, dicamba, glyphosate, metsulfuron and triclopyr provided better control in the latter method. The high efficacy of the restricted use 2,4-D suggests that MCPA, an analog of 2,4-D and unrestricted, should be evaluated because it should provide a cheap, non-persistent, unrestricted herbicide for tropical ash management. Pat Bily (TNC Hawaii) reported good control with undiluted triclopyr amine applied to frills but only saplings were susceptible to triclopyr ester applied basal bark. However, HAVO staff reported control with triclopyr ester at 5% product in diesel oil applied to basal bark (Chris Zimmer, HAVO)" (Motooka et al., 2003).