The Eastern Redbud (Cercis ) tree provides a delicate supplemental beauty to early spring gardens in southern Ontario. It welcomes spring with clouds of deep magenta blossoms that cover its branches before leaf buds start unfurling. During summer it has a showy mass of heart shaped leaves. Fall foliage turns from green to a glowing yellow. In warmer areas of Ontario it is used as an ornamental specimen tree.
This is a deciduous tree worthy of space in urban gardens. Given excellent growing conditions it is easy to grow and will flourish. The scientific name canadensis suggests it is a tree native to Canada but this is controversial. At the time of naming this species as a native plant in Canada the status was based on an observation of the tree on the south end of Pelee Island in 1892 by Canadian botanist John Macoun. It is native to large areas of eastern USA south to Florida and west to Mexico. The tree was introduced into urban cultivation in 1641.
Cercis canadensis can grow to about 30 feet tall and 35 feet wide. Environmental stressors contribute to its short 20 year lifespan. Leaves are simple, cordate 3 to 5 inches across, arranged alternately. After blooms finish, green pods develop and remain on the tree until after leaf fall. Flowers form on small buds on old twigs, branches and along trunks. They are self-pollinating and bisexual.
The Eastern Redbud is grown as an ornamental in Ontario to zone 6 or zone 5b with no dieback. (www.planthardiness.gc.ca) Eastern Redbud will grow best in a sunny, protected south-facing spot in the garden. It should be planted in soil with good aeration, nutrient retention and excellent structure. Cercis canadensis is prone to multiple trunks so formative pruning may be used in winter to help the young tree create a strong structure. Too much pruning spurs new growth which can cause excess stress on the young tree through the open pruning wounds, allowing moisture and pathogens to enter. With optimal growing environment, growth is rapid for saplings. They can gain 7 to 10 feet in the first six years. Flowering can begin in the fifth year. While young trees can tolerate some shade, a mature Redbud needs full sun.
This tree is best transplanted balled-and-burlapped or container grown as a sapling. Young redbuds have the best survival rate when planted in spring or fall. In their book Diseases of Trees and Shrubs authors Sinclair and Lyons describe more than ten potential contributors to the Redbud’s reputation of being short lived. These include leaf anthracnose, canker, dieback,verticillium wilt and insects.
Gardeners will need to destroy affected parts, remove visible pests by hand or release natural enemies to hunt and kill pests without harming the tree. Parasitic wasps could be encouraged to live in the area of the Redbud trees. Environmental threats include artificial lighting to which it has an intermediate resistance.
Redbud is drought resistant but cannot tolerate salt. This tree has some resistance to root disturbance and compaction.
This flowering tree is a lovely ornamental specimen tree and even more impressive when planted as a grouping or naturalized in woodland. If the spring is cool enough it can bloom for three weeks. It is best added as a subtle touch of beauty among other more long lived trees in the yard.
A companion plant to consider is Flowering Dogwood (Cornus florida). Redbud has the advantage of being able to withstand the toxic juglone of Black Walnut (Juglans nigra) trees and can grow near them. Though cultivated as a garden planIng it also grows as an understory tree in forests further south. This tree provides early spring food for bees.
The blossoms attract hummingbirds. Cardinals and grosbeaks eat its seeds. In its native setting this tree has shown adaptability growing from moist stream edges to dry ridges. However, as a tree in the garden it will flourish best on a sunny, moist but well drained slope in soil with good tilth. Growing this tree mindful of its needs can be a rewarding gardening experience. Redbud is now popular in southern Ontario and Quebec largely because people think of it as a tree native to Canada. The Eastern Redbud, beautiful throughout the growing season, qualifies for a strong presence in our urban gardens.
— Kay Verdone, Guelph Wellington Master Gardener