Thinleaf alder (Alnus incana ssp. tenuifolia), Truckee River. Photo: K. Fitzgerald.
Thinleaf alder
Alnus incana ssp. tenuifolia
- Tall shrub or small tree
- Grows directly along river’s edge
- Leaves: Oval, 2-4” long, with coarse, double-toothed edges
- Bark: smooth, red/gray/brown in color
- Flowers: Small “catkins” bloom in early spring (Feb-June). Male are long, soft, and hanging; female look like tiny pine cones.
Species Description
Thinleaf alder, the western subspecies of Gray alder (A.incana), grow along the banks of the Truckee close to the water’s edge. They are fairly tolerant of flooding, and help hold riverbanks in place with their roots during times of high water.
Alders are monooecious, meaning that both male and female reproductive parts (called catkins) are present on the same plant. On Thinleaf alder, catkins develop during the end of the growing season and bloom the following spring (Fryer 2011).
Alder are Nitrogen-fixers; their roots are infected (in a good way) with actinomycete bacteria, which live inside nodules in the roots, trap atmospheric nitrogen from the air, and transmit it to the host plant (Fryer 2011; Lanner 1983). This is symbiosis: a relationship between two species in which each benefits. When alder leaves drop to the ground in the fall, they release nitrogen to the water and soil, providing nutrients for the entire ecosystem (Mozingo 1987).
Additional images:
Thinleaf alder (Alnus incana ssp. tenuifolia), Truckee River.
Thinleaf alder (Alnus incana ssp. tenuifolia), Truckee River. Feb 2015.
References & Links
Fryer, Janet L. 2011. Alnus incana. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/plants/tree/alninc/all.html [2016, January 22]
Lanner, R. M. 1983. Trees of the Great Basin: A Natural History. Reno: University of Nevada Press.
Mozingo, H. N. 1987. Shrubs of the Great Basin: A Natural History. Reno, NV: University of Nevada Press.
USDA. 2015. Alnus incana. USDA Plants Database. US Department of Agriculture, Natural Resources Conservation. Service: http://plants.usda.gov/core/profile?symbol=ALIN2 [2015, February 20]