In the snow-covered winter landscape, the beauty we can remember from other seasons when the plants were in bloom or filled with glorious green foliage are often missing.
It leaves both humans and wildlife in search of plants that will retain interest either in the form of decorative beauty for us or as protection and habitat for all of the animals that share our landscape.
I think we all, as gardeners, strive for plants with four seasons of decorative appeal, and often compromise for a season of less interest. Perhaps the off-season interest in wildlife can help fill the void for some of these plants that just don’t quite fit the bill as four-season show-stoppers.
The river birch (Betula nigra) is one of those plants that I particularly notice in winter because of its unusual bark character. In addition, the often multi-stemmed habit at eye level provides ample knot structure for the gorgeous, curling bark that flakes in a variety of colors from creamy white to rusty orange or even pale browns. Beyond its bark, it boasts excellent fall color, as well as a showy spring flower display that creates multiple seasons of beauty.
This native tree is very adaptable and grows quickly. Its home territory spans much of the eastern United States. It is usually commonly found in river banks, swamps, and basements connected to river systems. Similar to many other ground trees, the river birch has a root system that can be adapted to soil conditions with low oxygen levels and poor drainage. This adaptability is well suited to the urban environment as many sites have similar conditions due to soil compaction.
When someone asks me what I recommend for a fast growing shade tree, river birch is often one of my first choices simply because of its beautiful bark and excellent adaptability to most locations. However, it has a relative weakness: it does not tolerate alkaline soils or high pH soils that are occasionally found in urban environments.
In these locations, the river birch can develop an iron deficiency, commonly known as chlorosis, which affects its health and appearance. This condition can be recognized by the yellowing of the leaves, which keep their green color along the veins. It’s a fairly distinctive pattern on leaves with a sharp contrast between yellow on the outer edges of the leaf and inner green areas on the veins.
Iron chlorosis can be treated fairly easily by adding a soil acidifier to lower the pH. However, a significant change in pH is a slow process that often requires multiple applications over multiple seasons. Even so, I recommend river birch, as locations with alkaline soils are usually in the minority and the condition can be corrected.
In addition, unlike some non-native birch trees such as the white birch (Betula papyrifera) that are commonly planted in Illinois and suffer from a range of diseases, it is relatively free of insect pests and diseases.
While the river birch’s attractive bark could arguably offer four interesting seasons, its noticeability seems to wear off in summer with a full crown of leaves and other green plants surrounding it in the landscape. Summer is likely the time of the least decorative uniqueness to humans, but it is possibly one of the greatest times of interest to wildlife.
Because the river birch is native to Illinois, it provides valuable habitat for a number of native insects that use this tree as food and shelter during the growing season. It is a vital source of food for over 45 species of moths in Illinois as their larval forms feed on river birch trees.
Some species of butterflies also use this tree in its larval form. Over two dozen other types of insects, including wood beetles, leaf-eating insects, fly larvae, and others, also use river birch.
I think the insect life this tree supports in the summer far outweighs any loss of decorative appeal. However, when you factor in other wildlife species, it also supports eight species of birds that feed on buds and seeds year-round. It is a popular nesting tree for squirrels and provides a hunt for white-tailed deer in winter.
All in all, the river birch is an excellent specimen for the landscape, with great wildlife value and widespread availability in various sizes in most kindergartens and garden centers.
Ryan Pankau is a UI Extension horticultural educator serving Champaign, Ford, Iroquois, and Vermilion Counties. This column also appears on his ‘Garden Scoop’ blog at go.illinois.edu/GardenScoopBlog.