Weigela are fast-growing flowering shrubs with trumpet blooms that attract butterflies and hummingbirds to your garden. Pruning at the right time, in the right way, and for the right purposes can enhance your weigela's strength, health, and flowering abundance. Follow these tips to prune your weigela successfully and meet your long-term goals for its growth.
Step 1 - Use the Pruning Shears Correctly
Never use electric hedge trimmers on weigela, as this will leave a wide swath of open wounds on stems and canes where mold-based diseases can invade the plant. Trim canes, twigs and branches by hand, one at a time. Always cut above a flower bud or a shoot where a new twig will appear. Make an angled downward cut on the twig or cane to prevent crushing the twig. This will damage the twig and take a whole season to heal. Sharpen the shears yearly after each pruning.
Step 2 - Prune to Promote Flowering
In the summer, prune all of the weigela tips with flowers back by about 2/5 of their length. This will promote new growth and more flower buds for next spring. The flowers grow out of stems and canes that developed in the previous year. Avoid spring pruning, as you will lop off flower buds before they can bloom.
Step 3 - Prune to Maintain Shape and Desirable Growth
At the same time, look over your weigela shrubs as a whole. If they have become unruly and leggy, trim back the undesired growth, to maintain a cultivated appearance. Weigela that look as though they have run wild do not suit a garden. However, do not use hedge clippers for shaping plants such as weigela into a topiary shape. This will restrict their growth and blooming. Check for branches and canes that are crossing each other and thin these out. Weigelas need airflow and sunlight at the core to maintain the strength to keep producing leaves and flowers. As well, look for any branches near the roots that are spreading horizontally along the ground. Prune these right back to where they extend from the root. They can serve as vectors for fungi that will attack the roots.
Regenerative pruning will also help your weigela grow stronger. Cutting back about one in every three main canes will encourage new growth. In subsequent years, these new twigs and branches will increase in diameter, becoming as strong as the stems that were pruned. Do regenerative pruning about every three years.
Step 4 - Prune to Remove Dead and Diseased Branches and Canes
Inspect your weigela regularly for dead and diseased canes and branches. These are an ideal medium for the growth of fungi. Diseases such as twig blight can spread rapidly from the tips unless recognized and eliminated early. With very sharp pruning shears, cut below diseased limbs, but above flower buds and leaf stems. Disinfect the shears between each snip with hydrogen peroxide or rubbing alcohol. Chlorine bleach can corrode the steel blades of your shears.
Effective pruning of weigela in the late summer will help it overwinter, prevent disease, and encourage masses of colorful blooms.