by Hillary Sellmeyer,
Native Plants Class
Common names: Rocky Mountain boxelder, Manitoba maple, inland boxelder,
ash-leaved maple (3).
Family: Aceraceae.
Synonymy: Acer interius Britt., Acer negundo
L. ssp. interius (Britt.) A.& D. Löve,
Negundo aceroides (L.) Moench ssp. interius (Britt.)
A.& D. Löve,
Negundo interius (Britt.) Rydb (5).
Etymology: The specific epithet is derived from a Sanskrit name
for trees having leaves similar to those of the box elder (1).
Identification
Growth form: Rocky Mountain boxelder is small to medium sized tree
with a single trunk. It can attain a height of 80 feet (4).
Roots: The root system of Rocky Mountain boxelder consists of
a short tap root and long branching lateral roots. Due to the spreading
nature of this root system, this tree is important for erosion prevention
(2).
Stem: Branches arise from the base of the gray woody trunk. Branches
remain close to the ground throughout the tree's lifespan resulting
in an irregular crown. The twigs are hairy and green.
Leaves: Leaves are pinnately compound and opposite. Each leaf
consists of 3-7 leaflets that range from 5-11 cm in length. Leaflets
have roughly toothed margins. The underside of each leaf is paler and
has a greater number of hairs than the upper surface. Mature leaves
are covered in fewer hairs than juvenile leaves. Terminal leaflets are
the largest.
Inflorescence/flowers: Flowers are incomplete and lack
petals. Inflorescences are droopy, yellowish-green aggregates of flowers
(3/16 in. long).
Fruit: Seed cases (up to 1.5 in. long) are V-shaped and winged.
They are clustered in pairs around the inflorescences. Seed cases are
red when young, and turn yellow upon maturity (4).
Similar species: Acer glabrum Torr. and Acer grandidentatum
Nutt. are relatives of Acer negundo, and are both native to
North America. Acer negundo is easily distinguished from these
other species by pinnately compound leaves (vs. simple leaves in Acer
glabrum Torr. and Acer grandidentatum Nutt.).
Ecology
Life history: Rocky Mountain boxelder is a perennial with an average
life span of 75 years (4).
Native/introduced: Native.
Photosynthetic pathway:
Phenology: Rocky Mountain boxelder blooms from April to May (3).
Upon maturation, seeds are dispersed by wind.
Distribution: Alberta south to Arizona; east to Minnesota and
Missouri. In Arizona, Rocky Mountain boxelder is found in Mojave, Coconino,
Navajo, and Yavapai counties near riparian areas in oak woodlands and
ponderosa pine forests. Its elevation range is 3500-8000 ft (5).
Uses
Ethnobotany: Sap is extracted from Rocky Mountain boxelder in
areas where sugar maple does not grow. The sap is used to make sugar
and syrup (2).
References
1. Athenic
Systems. Tree Guide, Inc. http://www.athenic.com/index.htm.
(5 Dec. 2002).
2. Crittenden
M. Trees of the West. Millbrae: Celestial Arts; 1977. 157-158 p.
3. Epple AO. A Field
Guide to the Plants of Arizona. Guilford: The Globe Pequot Press;
1995. 104 p.
4 Stuart JD,
Sawyer JO. Trees and Shrubs of California. Los Angeles: University of
California Press; 2001. 130 p.
5. USDA, NRCS. 2002. The PLANTS Database, Version 3.5 (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.
