How to Grow Redbud Trees From Seed
A cloud of white or pink blossoms cover the redbud trees (Cercis canadensis) in spring, before the leaves appear. The pollinated flowers develop into pealike seed pods. While redbud trees are members of the Legume family, their seeds are not soft like peas and beans. They are extremely hard and slow to germinate unless scarified and stratified before planting.
Gathering and Preparing the Seeds
The pealike pods of the redbud contain four to 10 1/4-inch hard brown seeds. Collect the seeds from the trees in fall, when the pods are dry. Allow the pods to air-dry for several days, until they are completely dry. Then the seeds can be stored in a sealed container at 35 to 41 degrees Fahrenheit.
Scarify the seeds by sanding briskly along one side to remove part of the hard outer shell. Avoid damaging the delicate inner embryo. As an alternate method of preparing the seeds, you can drop them into boiling water for one minute.
After scarifying the seeds, they require cold stratification. Place the seeds in moist peat moss or sand in a plastic bag. Clearly label the bag as "Redbud seeds" with the date before storing it in the refrigerator for five to eight weeks.
Germinating the Seeds
Fill peat pots with moistened seed-starting mix and place them on a tray. Immediately after removing the stratified seeds from the refrigerator, plant one seed in each pot, pressing it 1/4 inch into the soil. Cover the peat pots and tray with plastic wrap. Place the tray in a warm, brightly lit location until the seedlings appear. Remove the plastic wrap. Water when the soil is dry to the touch, to maintain a consistent moisture level in the soil.
You can also plant redbud seeds outside in the garden. Plant the seeds in a well-drained, partially sunny location, 1/4 inch in the soil. Keep the soil moist but not waterlogged. Redbud trees do not like transplanting; plant the tree in its permanent location.
Planting the Trees
Plant the trees in well-drained locations in the garden. Morning sun and dappled afternoon shade replicate the trees' natural habitat as understory trees in the forest. While redbud trees are hardy in U.S. Department of Agriculture plant hardiness zones 4 through 9, seedlings should be planted after the last frost date so they have a full growing season before cold weather arrives again.
Dig a hole twice the width of each peat pot and at the same depth. Tear off the upper rim of the peat pot so that no part of it extends above ground after the seedling is planted. This prevents the exposed portion of the peat pot from wicking moisture away from the tree's roots. Place the seedling in the planting hole and backfill with the excavated soil. Water the seedling thoroughly.
Watering and Fertilizing Redbuds
Redbud trees prefer a moist but not soggy soil. Water weekly, or when the soil is dry to a depth of 3 to 4 inches, at a rate of 10 gallons for every inch in diameter of the tree's trunk. Adding 3 to 4 inches of organic mulch around the tree helps slow the evaporation of water from the soil, helping to maintain an even level of moisture around the tree's roots. Spread the mulch over the soil, 12 inches from the tree's trunk and out to the drip line.
Redbud trees are not heavy feeders and the nutrients from the decomposing mulch are generally sufficient to nourish the tree. If the soil is very poor or sandy, fertilize with a slow release 5-10-10 or 10-10-10 fertilizer at a rate of 1/2 pound for every inch of the tree's trunk. Scratch the fertilizer into the top 2 to 3 inches of soil and water thoroughly.