Eastern Redbud

Site and soil

Redbud is an understory tree by nature, so it will take more shade than most fruit and nut trees will. Illinois Extension notes that redbuds grow best in full sun but can tolerate partial shade, with flowering reduced, and that they tolerate a wide range of soils as long as those soils are well drained. Clemson Extension adds that redbud grows well in full sun but prefers some shade in the heat of summer, takes acid or alkaline soil, and dislikes permanently wet sites. The short version: give it morning sun, a little afternoon relief, and ground where water never stands.

NC State Extension lists the species as hardy in USDA zones 4 through 9, pH adaptable, and happy in moderately fertile clay or sandy soil, though not wet soil. Maryland Extension puts the best ground at loam, sand, or clay with high organic matter, moist to occasionally dry, and well drained, which is what the humus rich, well drained note on this listing means in practice. Good spots on a hill farm are a forest edge, an east facing slope, or the second story under taller canopy trees.

Spacing

Mature height runs up to about 30 feet. NC State Extension gives a mature spread of 20 to 35 feet wide; Clemson Extension gives 15 to 35 feet. The 6 to 12 foot spacing on this listing is for close rows, hedgerows, and alley plantings where you want the canopies to knit together into a flowering understory line. For one tree carrying a full rounded crown, allow 20 feet or more of open ground. Clemson notes that sun grown trees stay compact and rounded while shaded ones grow looser and taller, so a tree tucked under canopy will reach up rather than out.

Planting

Plant it where you mean to keep it. Clemson Extension advises transplanting redbuds while they are very small, because they have difficulty surviving a move once the root system has developed. Pick the spot once and commit to it. The steps below follow the Clemson Extension factsheet on planting trees correctly.

• Dig the hole no deeper than the height of the root ball, and at least twice, preferably up to five times, wider. Loosen the sides so new roots can push out into the native soil.
• Set the tree so the topmost layer of roots sits level with the soil surface. In heavy or compacted ground, set it 2 to 4 inches higher than the surrounding soil rather than lower.
• Backfill with the loosened soil you dug out, mixed with no more than 10 to 20 percent compost. Break up the clods first, since they leave air pockets around the roots, and do not tamp so hard that you compact the soil.
• Water the root ball itself at first, since the roots have not yet reached the surrounding soil. A low ring of soil around the edge of the hole holds the water where it is needed.
• Spread 2 to 4 inches of organic mulch over the planted area, then pull it back so it does not touch the trunk. Clemson is plain about why: mulch against the stem raises the chance of stem rot. Water slowly and well after mulching.

First-year care

The first season is about roots, not top growth. Clemson Extension says to keep the root ball at constant moisture, not saturation, for the first few months after planting, and to check more often on a site that dries out fast. In practice that means a slow, deep soaking whenever the top inch of soil under the mulch has dried, and more attention in sandy ground or a long dry spell. Clemson also warns that drought stressed redbuds are more vulnerable to Botryosphaeria canker, so a dry first summer is the one to watch.

Keep the mulch ring wide and the grass out of it; turf pulls water from the same few inches of soil the young roots are working. Illinois Extension reports that when young, redbuds grow moderately fast, reaching 7 to 10 feet tall in five to six years, and then slow as they mature. So most of what year one buys you is a thicker stem and a better root system rather than visible height.

Pruning

Redbud needs very little pruning. Take out broken, rubbing, or dead wood, and lift the lowest branches only where the tree sits near a path or a patio, which is the one case Clemson Extension calls for: low limbs pruned for clearance where the tree grows near walkways or patios.

Two rules matter more than shape:

• Prune when the stems and foliage are dry. That is Clemson Extension's wording, and the disease it has in mind is Botryosphaeria canker, which causes branch dieback. Clemson is blunt that there are no fungicides to control it, so pruning out diseased branches and disposing of the cuttings is the control.
• Cut well below damage. Where you find a sunken, cracked, or diseased area on a stem, Clemson Extension says to cut the stem 6 to 8 inches below it rather than trimming back to the edge, and to disinfect the pruners between cuts with rubbing alcohol.

Go easy on the old limbs. Illinois Extension points out that redbuds will occasionally produce flowers on their trunks, a habit called cauliflory, and the flower clusters sit along mature wood, so the old wood you remove is the wood that blooms. Watch for Verticillium wilt and Botryosphaeria canker as the tree ages; Maryland Extension lists both, along with leaf anthracnose, as the species' main troubles, and Illinois notes that healthy trees often live 50 to 75 years while stressed or infected ones fall well short.

Harvest

There are two harvests here, and neither is a fruit crop in the ordinary sense.

The flowers come first, ahead of the leaves, and they are edible. Illinois Extension puts it plainly: the flowers of redbuds are also edible, and can be eaten fresh, where they taste similar to peas, added as a garnish to salads, pickled, fried, and used to make jelly. NC State Extension puts the bloom from March into May, which gives you a long picking window in spring. Pick lightly from a young tree and leave the bulk of the bloom to the insects. Illinois Extension notes that because redbuds bloom so early they can be important food sources for early season pollinators such as bumble bees and carpenter bees, weeks before the rest of the orchard wakes up.

Flat seedpods follow, turning from green to brown through summer and fall, and NC State notes they can hang on through fall and even winter. Maryland Extension notes that some songbirds, such as northern cardinals, eat the seeds. If you want to raise more redbuds from your own pods, the USDA Forest Service reports that in nursery practice both scarification and cold, moist stratification are required for germination; seed sown straight out of the pod will simply sit.

On timing, expect a few years before the first pods. The USDA Forest Service reports that pods may be borne by a 5-year-old eastern redbud, that first reproduction on average comes when a tree is about 15 feet tall, and that good seed crops usually occur in alternate years. Pollination is not something you have to plan around: Maryland Extension describes redbud flowers as self-pollinating and insect-pollinated, so a single tree will set pods on its own. A second tree is for your own pleasure and for the bees, not for fertility.