It all starts with that "oops" feeling you get when you suddenly realize that your favorite weigela shrub -- heavy with its lovely, bell-shaped flowers -- cannot stay in its current location. Although it's easy to blame yourself, remember that backyard plans can change radically and unexpectedly in the blink of an eye. Your best bet is to spend that energy mapping out a careful strategy for transplanting the wiegela (Weigela spp.) successfully in late fall or early spring. You'll have to start months before the actual move with root pruning.
When to Transplant
Most deciduous shrubs, including weigela, transplant best in early spring or late fall. Moving a shrub during those periods causes it the least transplant stress. For spring transplants, wait until after the soil has thawed but act before the shrub has started to bud out. Fall transplants must happen after the leaves have fallen from the plant but before the ground freezes. The exact dates vary between regions. For example, experts at the New York Botanical Garden suggest that, in that region, transplanting be done between March 15 and May 1, or Oct. 15 and Dec. 1, but this schedule won't work everywhere.
A good rule of thumb for fall planting is to get the transplant into the ground at least four weeks before temperatures drop below 40 degrees Fahrenheit.
Prune Roots for Compact Rootball
Transplanting is notoriously difficult for established weigela shrubs because of the many feeder roots the plant will lose. These are the small roots that bring food and water to the shrub. It is simply not possible to dig out a rootball big enough to contain all of a weigela's feeder roots, and the less roots it travels with to its new location, the more stress it experiences.
Root pruning can help. Root pruning involves clipping the plant's roots six months before the transplant so it grows a compact new feeder-root system that can move with the plant. You should transplant a weigela in late fall or early spring, so count back six months and note the date for root pruning. Never root prune a weigela unless it is dormant.
To root prune, use a sharp spade that has been disinfected and slice vertically into the ground in a circle around the plant. The size of this circle should be a little bit larger than the projected size of the rootball to be transplanted, which depends on the height of the plant. A weigela 48 inches high requires a root ball 20 inches in diameter and 14 inches deep, so you should root prune in a circle somewhat larger than this. It helps to draw a circle on the soil before you begin digging with the spade. The taller the shrub, the larger and deeper the rootball must be.
Because weigela is deciduous, you can tell when it's dormant because it is losing or has lost its leaves. Note that weigela cultivars bloom in U.S. Department of Agriculture plant hardiness zones 4 through 8.
If the weigela has been in the same location for several years. you may be better off digging a trench around the shrub, some 8 inches wide, cutting the roots as you go. When you are done, refill the trench with the extracted soil and water the soil in well.
If you live in a climate with very cold winters, be careful to transplant early enough in autumn to give the plant a chance to establish its roots before the winter arrives. A safer alternative is to transplant in spring when all chance of a freeze is past.
Digging Out Weigela
Before you begin digging out the plant, prepare its new home. Select a spot in full sun or partial shade with fertile, well-draining soil. Dig out a hole several times the size of the rootball and mix organic compost into the extracted soil. Water the shrub well.
Mark a north-facing branch and the soil line on the trunk of the plant. Dig another trench around the tree just outside the root-pruning trench but the same depth. Slide the shovel beneath the root ball soil at an angle of about 45 degrees to cut any roots attaching it to the ground.
The best way to protect the rootball as you transport it is to wrap it in burlap.
- Tilt the root ball to one side, place the burlap beneath it, then tip it to the other side and pull it through.
- Pull the burlap around the ball and tie the corners at the top.
- Wrap twine around the burlap to strengthen it.
Fill the bottom of the hole with extracted subsoil soil so that, when you place the shrub into it, it will be at the same level it was planted before. Remove the burlap and set the rootball into the center of the hole, making sure to keep its north/south orientation the same as it was before. Fill in the outside of the hole with extracted subsoil, pressing it carefully around the rootball with your fingers. Water slowly and thoroughly -- at least 1/2 gallon of water per square foot of soil -- to settle the subsoil. Finish by adding the top soil around the rootball, pressing it into place and watering again generously.
If you are transplanting more than one weigela, space the shrubs at least 12 inches apart.
Do not fertilize the weigela during transplant. You want the shrub to put all its energy into building a root system.
From Alaska to California, from France's Basque Country to Mexico's Pacific Coast, Teo Spengler has dug the soil, planted seeds and helped trees, flowers and veggies thrive. A professional writer and consummate gardener, Spengler has written about home and garden for Gardening Know How, San Francisco Chronicle, Gardening Guide and Go Banking Rates. She earned a BA from U.C. Santa Cruz, a law degree from U.C. Berkeley's Boalt Hall, and an MA and MFA from San Francisco State. She currently divides her life between San Francisco and southwestern France.