Redbud trees, also known as Judas trees, are native to North America where they are grown as ornamental landscape plantings. Numerous cultivars exhibit a range of pink shaded buds and growth patterns. The trees are tolerant to U.S. Department of Agriculture hardiness zone 4, an area that reaches 20 degrees below zero during hard winters. Though tolerant of these conditions, not all redbud trees survive a winter unharmed.
Eastern redbud trees can tolerate cold, but trees must be healthy to withstand these stressful conditions. Even when trees are unaffected by cold they can be killed back by early unexpected frosts, by heavy snow and ice damage and by wind exposure. Siting your tree is just as important as planting it within a growing range to which it is adapted. Plant redbud away from building edges and windy sites. Shield your tree from winter sun to discourage early bud development. Premature, tender buds are killed off by late season frosts.
Redbud trees that have experienced twig kill and bud kill, or those with less than 50 percent of their lateral branches killed back, can recover from a harsh winter with drastic pruning. Prevent excessive tree stress by drastically pruning your tree over several growing seasons. Remove heavily damaged branches first, cutting at an angle upwards from the tree's trunk. Keep the branch collar intact as this will prevent bark stripping. This technique also aids in the branch's regrowth attempts. Do not cut back more than 1/3 of the tree's branches. Pay attention to foliage recovery, rather than concentrating on flowers. Your redbud may look less than optimal for several growing seasons but it should recover from winter damage.
Aside from choosing a protective site for your ornamental redbud, providing proper maintenance helps prevent winter kill-off. Apply a balanced fertilizer to the tree's base in early spring. Prune the redbud annually in early spring. Redbed wood is brittle and weak. Removing weak joints and loose branches prior to freezing weather helps keep branch loss during ice storms at a minimum.
Roots are responsible for healthy branch and shoot development. Protect root systems by applying a loose mulch to the plant's base. Ensure that the soil is is well aerated and provides adequate drainage. Water pooling is destructive to root systems and puts the plant's structural integrity at risk. Water deeply every few weeks. Frequent, shallow watering does not help root structure.
Choose a redbud species that is adapted to your growing region. Cercis canadensis cultivars Royal White, Tennessee Pink and Forest Pansy are cold-hardy varieties. Lavender Twist, also called Covey, is suited for warmer climates. In hot, humid climates the trees are susceptible to powdery mildew, verticillium wilt and cankers. Avoid these diseases by providing plenty of room around your redbud, planting at a distance from other plants. This allows air circulation between branches and prevents the development of these infestations.
- USDA Plant Guide: Eastern Redbud
- University of Georgia Cobb County Extension; Redbud Tree; Michele Brown
- University of Missouri Extension; Ice and Freeze Damage to Ornamental and Fruit Trees - Implications and Remediation; Chris Starbuck, Michael Warmend; March 2008
- Fine Gardening: Genus Cercis Plant Guide