Saturday, March 23, 2013

Redbuds - The "Perfect" Tree

Our Plant of the Week on "Garden Talk" this week is the eastern redbud, Cercis canadensis. After discussing this tree with co-host Dr. Sue Hamilton, Nancy Schneider (woody plant specialist at Stanley's Greenhouse) and UT horticulture student David Pease, I have concluded it must be the "perfect" small tree for the Tennessee Valley region.
Besides welcoming spring with its display of pink blossoms, the eastern redbud offers the gardener many advantages. It grows easily in most soils. Because it is a legume, it actually helps to build the soil underneath it, by fixing atmospheric nitrogen with the help of bacteria living on the roots. Although tent caterpillars sometimes find the tree tasty, they are generally easy to control. The redbud has few other insect pests. Older trees are susceptible to trunk canker, a fungal disease that eventually kills the tree, although many specimens endure for a long time before succumbing to this problem. Otherwise, redbuds are carefree.

Transplant redbud trees from late fall until early spring. Container grown specimens typically bloom the year they are transplanted. Set the plants slightly higher than the surrounding soil, in order to avoid covering the crown. Water in and mulch. Irrigate if rainfall is insufficient. After the first season, the tree will be much more drought tolerant. Fertilization is not needed and may reduce bloom. Adaptable to many soil types, the redbud does best in well-drained, moisture retentive soil with organic matter.

Redbud trees grow easily from seeds, which are borne in pods that look like small snow peas. As a result, many cultivars and selections exist. Some of these are:

  • 'Alba' -- a white-flowered form (f. alba) that comes true from seeds, sometimes incorrectly sold as 'Texas White"
  • 'Dwarf White' -- another white-flowered redbud, it remains under 10 feet tall
  • 'Forest Pansy' -- with new foliage that is deep burgundy red, this variety blooms later than the wild type
  • 'Silver Cloud' -- white leaf variegation on a tree that prefers light shade
  • 'Pink Heartbreaker' -- a weeping form that does not need staking to remain upright
  • 'Covey' -- a dwarf weeping form that grows upright only if staked; unstaked plants will sprawl and become a ground cover

Besides our native eastern redbud, other species are sometimes available in garden centers. These include the western, or California, redbud (C. occidentalis) and the Chinese redbud (C. chinensis). The California redbud forms a multi-stemmed shrub when grown in the Tennessee Valley and is more sensitive to trunk canker than the eastern species. Chinese redbud is resistant to trunk canker, but grows much larger than the North American species, about 40 feet.

Flowers of the redbuds are edible. Native Americans used redbud for medicinal purposes. The flowers can be fried in batter, or mixed with nuts and honey or chopped dried fruit. Flower buds may be pickled like capers, and the green seed pods can be used much like snow peas in sautes and stir-fries. Honeybees and other pollinators are attracted to redbuds, and the eastern redbud is the host plant for Henry's elfin butterfly (Callophyrus henrici).

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