TheMondayGarden.com

The Monday Garden, February 13, 2005, Issue 151
Eco-gardening at its best

In North America, we have a good half-dozen native alders, the best know probably being the Western red alder (Alnus rubra), famed for pioneering burned area and for its lovely hardwood. The alders are members of the birch clan and as such are nitrogen fixers. Research shows that alders actually helped change the North American climate back in the Ice Age by pulling nitrogen out of the air and depositing it in the soil in usable form.

picture: The native speckled alder (Alnus incana f/k/a A. rugosa) in the swamp at the Bartlett Arboretum, Stamford CT, August 2004. Note the cute little green cones and the alternate leaves, common to all alders. The speckled alder’s leaves have perfectly parallel, directly opposite veins that run straight to the double- saw toothed leaf edge; the leaves have a quilted appearance and are pointed at the tip but round at the base. Note also the light colored speckles (lenticels) along the twig. In Connecticut, the cold-loving speckled alder is at the southern tip of its range.

Alders are often found along streams and in the fresh water wetlands. In my area, alders grow in mix stands with other swampy trees and shrubs, include the native red maple, winterberry ilex, sweet pepper, and cornus, all of which benefit from the alder’s production of nitrogen.
____________________________________________________________

The Monday Garden, February 20, 2005, Issue 152
Eco-gardening at its best

The birches, to me, are almost as interesting as the maples, and that’s saying a lot. The Betulaceae clan, as the whole family is called in Latin, includes alders, birches, hornbeams, filberts and hazels. There are so many interesting things to say about each of these trees, that each deserves its own article. This is a look at the bark and other identifying characteristics of the major birches found in the Northeast.

In North America, we have 20 or so native birches, plus a bunch of imports, one of which, the European (Betula pendula), has widely “naturalized” in the Northeast and Northwest. In my part of sub/urbia, birches divide roughly into the downtown crowd of black-and-white dressing, fussy, fast-living, slender, graceful small-to-medium trees found near the malls and high-rises, and the up-town crowd of majestic, if equally fussy, slow-growing, long-lived valuable hardwood trees that grow in the forests north of town where private houses are built on lots measured in acres.

picture: Yellow birch’s catkins and last year’s leaves. Bartlett Arboretum, Stamford CT, Feb. 2005. Most birch leaves are double-toothed with parallel veins in a “V’ running straight to the leaf edge. The yellow’s have finer teeth, a tapering point, and alternate leaf veins. The male catkins on most birches come in groups of 1 to 3 at the branch tip; they are generally formed in the summer, stay on the tree of over the winter and bloom in the spring. The female catkins, which turn into green-then-brown cones, are shorter and further up the twig. Note also the shiny, reddish and slightly warty twigs.

Up-town you find the yellow (Betula alleghaniensis f/k/a B. Lutea) and black (Betula lenta) birches, tall trees of the deep forest that don’t come downtown. They are highly prized for their hardwood and much encouraged by foresters. Downtown are the white-bark birches prized by landscape architects and designers. The white-trunked ones include the native paper (Betula papyriera) and gray (Betula populifolia) birches, the naturalized European birch, and a handful of lesser-known nursery stock hybrids, dwarfs, and imports. The downtown crowd also includes the poodle-shaggy river birch (Betula nigra) (also called the red birch). The native and naturalized downtowners are also found in sunny spots up-town and along the rivers and beaches.