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Resources < Wildlife Habitats < Guide to Native Plants of Georgia for Wildlife < Alnus serrulata
The Alder is a tree of confusion, difficult to define what kind of tree it actually is. It is a beautiful tree that should be appreciated for its unusual characteristics. The Alder possesses traits of a wide diversity of unrelated trees, and is the dendrological jack-of-all-trades.
Like pines and other conifers, the Alder possesses small, dark cones that persist through winter. Like willows, its roots are fibrous and therefore hold it securely in wet soils and provide excellent erosion control. Like legumes, the Alder fixes nitrogen with the help of fungi in its roots.
Even the Alder’s actual growth is confused. Its shape is contorted and twisted, as though unsure of which direction to grow. Its often multiple trunks chaotically twist through the dense shade of wet forest understories as they search for pockets of light. The trunk is pleasantly muscled and fluted, with a lovely shape that differs markedly from other trees. Despite being such a copycat, the Alder, like a plant collage, has a beauty and originality that is truly its own.
Betulaceae (Birch)
A multi-stemmed deciduous small tree or large shrub. Bark is thin, gray to brownish, smooth, and muscled with a fluted trunk. Leaves are alternate, simple, obovate to elliptical, 2-4” long, and pinnately veined. They have a finely serrated undulating margin and are dark green above but paler and finely hairy below. Flowers are monoecious and appear in early spring; males are green-brown catkins, 1-1 1/2” long, while females are ½” long, and reddish. Fruits are woody, cone-like catkins, ½” long, dark brown with each scale enclosing a tiny, winged seed. Fruit ripens in fall and the cones persist through winter.
10-20 feet tall and 15-20 feet wide
Twisted, multi-stemmed deciduous small tree or large shrub
Moderate
Full sun to heavy shade
Alders require the moistest possible soils for growth. Plant them near water sources for success. Otherwise, if no water exists near its desired site, plant it in partial to dense shade and irrigate it with at least one inch of water applied twice per week. Mulch it heavily also, by raking 4-6” of leaves or pine needles under it.
Ornamental Value: Alders are small and beautiful trees. They hold exceptional winter interest because of their contorted forms, their persistent cones, and the excellent muscled or fluted shape of their trunks.
Utilize Alder near water. Possibilities include surrounding a pond, lining a river or creek, or near a water garden. They even tolerate flooding and may be employed in swamps or consistently moist pockets in the landscape. They provide exceptional erosion control and are extremely useful to naturalize. Excellent companions include black willow, sweetgum, river birch, lizard’s tail, possumhaw, and red maple.
One of the most important functions of Alders in nature is to provide habitat for fish and other aquatic species. Near water, their canopies often grow out over the water’s surface and provide important shade, while their dense root systems often provide sheltered sites for important parts of the food chain like insects. The seeds within the cones are eaten by a wide variety of songbirds.
The Alder is also unusual because it is host to a unique food chain of its own. Wooly Alder Aphids feed upon its sap. These aphids are the primary food source of the caterpillars—yes, carnivorous caterpillars, and the only such example in the insect kingdom!—of the Harvester Butterfly.
Native to swamps and banks of North America east of the Mississippi.
Seeds, root cuttings
Also known as Common Alder,
Hazel Alder
Text by Kevin Tarner, Georgia Wildlife Federation
Photos courtesy Robert H. Mohlenbrock @ USDA-NRCS PLANTS Database / USDA SCS. 1989. Midwest wetland flora: Field office illustrated guide to plant species. Midwest National Technical Center, Lincoln.
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