Eastern redbud

Identification and origin

Cercis canadensis belongs to the family Fabaceae, the pea and bean family. It is native to eastern and central North America, from the Atlantic coast and the southern Great Lakes to Florida, Texas and northeastern Mexico. In the wild it grows in open woodland, along forest edges and stream banks, and on dry ridges. It is the state tree of Oklahoma.

It is a small deciduous tree, often multi-trunked, that usually reaches 19.5–29.5 ft tall with a slightly wider spread. Young trees have an upright, vase-shaped habit; with age the crown spreads and becomes rounded or flat-topped. In sun it stays compact; in shade it grows taller, looser and more open. The scaly, reddish-brown bark develops fissures that reveal an orange interior.

The bloom is spectacular: before the leaves appear, clusters of four to ten small pea-like flowers, rose-purple to magenta, cover the branches and sometimes even the trunk. Flowers emerging directly from old wood like this is called cauliflory. The display lasts two to three weeks or longer. The heart-shaped leaves, 3–5 in across, emerge tinged with red, turn dark green in summer and yellow in fall, with a color that varies from year to year. The flowers are followed by flat pods 2–4 in long, green turning brown, each holding four to twelve seeds; they often hang on the tree all winter.

The genus name comes from the Greek kerkis, a weaver’s shuttle, which the pod resembles. The flowers feed bees, butterflies and hummingbirds early in the season, and birds eat the seeds.

Light

Redbud grows in full sun or part shade. In regions with hot summers, light afternoon shade suits it best; farther north, full sun gives the best results. It tolerates fairly dense shade but blooms much less there.

Watering

Regular, consistent soil moisture suits it best. After planting, water whenever the soil dries at depth until the tree is established. Once settled it tolerates moderate dry spells, but it suffers in prolonged drought and heat: during summer dry spells, regular watering keeps it vigorous. A tree stressed by lack of water becomes much more susceptible to canker. Mulch spread out to the drip line keeps the soil cool and moist in summer. Avoid soil that stays waterlogged.

Potting mix

It adapts to most soils, clay, loam or sand, and tolerates both acidic and alkaline conditions. It grows best in light, rich, moist, well-drained, moderately fertile soil. It does not tolerate poorly drained sites where water stands. It tolerates black walnut. It is very sensitive to herbicides and chemicals sprayed on lawns, so take care if you plant it in the middle of turf.

Temperature

It is a hardy tree, grown in USDA zones 4a to 9b. Hardiness varies a great deal with seed origin: a tree from a southern population can lack cold hardiness in the north, and a tree of northern origin can struggle in southern summer heat. Buy trees grown from locally collected seed whenever possible, especially in cold regions. In the coldest zones, twig dieback is common.

Repotting

Redbud belongs in the ground rather than in a long-term container. It develops a deep taproot and transplants poorly: plant it young, directly in its permanent spot, and leave it undisturbed. Young trees establish best when planted in spring or fall; container-grown trees can be planted any time. Choose a somewhat sheltered spot, because the brittle wood sometimes splits in wind or under heavy snow.

Pruning

Train it while young to build a strong structure. Avoid tight V-shaped forks, which split easily, and keep branches that form a wide U-shaped angle. Keep lateral branches less than half the diameter of the trunk and, on a single-trunk tree, space them 6–10 in apart along the main stem. Near a walkway or patio, remove low branches for clearance.

After that, simply remove dead wood. Prune when stems and foliage are dry, and disinfect the blades with rubbing alcohol between cuts: pruning wounds are the entry point for the fungi that cause canker.

Propagation

The species is easily grown from seed. Seed sown as soon as it ripens, directly outdoors in fall, germinates without treatment. Dried seed has a hard coat: it needs mechanical scarification or a hot-water soak, followed by cold, moist stratification for five to eight weeks before sowing. The tree sometimes self-seeds, but usually not enough to become a problem.

Cultivars do not come true from seed: they are budded onto seedling rootstock or rooted from summer cuttings under mist. Common choices include ‘Forest Pansy’, with purple foliage that greens in summer heat; ‘Hearts of Gold’, with golden-yellow spring foliage; ‘Appalachian Red’, with fuchsia-pink flowers; ‘Ace of Hearts’, a compact form; ‘Royal White’ and forma alba, with white flowers; and ‘Covey’ (Lavender Twist) and ‘Ruby Falls’, with weeping habits.

Common problems

• Branches that wilt and die suddenly: canker, the tree’s main disease. The fungus enters through a wound or dead branch, forms a dark, sunken lesion, then girdles the branch. No chemical control works: cut the branch 6–8 in below the affected area, avoid wounding the bark and water during droughts.
• Overall decline of the tree: verticillium wilt can kill it; ‘Forest Pansy’ is susceptible.
• Spots on the leaves: leaf spot diseases in wet weather, rarely serious. Powdery mildew and blights can also appear.
• Pests: scale, leafhoppers, treehoppers, caterpillars and webworms, Japanese beetles and borers, which mostly attack older or weakened trees.
• Pods considered untidy: the sterile cultivars ‘Flame’ and ‘Pink Pom Poms’ do not produce them.

A single symptom can have several causes: before acting, check watering, drainage, bark wounds and the year’s weather.

Toxicity

No toxicity is reported for dogs, cats or people. The flowers are even edible: they taste like peas, are rich in vitamin C, and can be eaten raw in salads or fried. If an animal shows unusual symptoms, contact a veterinarian.