How to Trim Lilac, Rose of Sharon and Forsythia Bushes

Bushes including lilacs must be pruned at the right time to flower.

Lilac, rose of Sharon and forsythia are all popular ornamental shrubs that can suffer from improper pruning practices. Pruning an ornamental shrub such as rose of Sharon, lilac or forsythia should be undertaken as soon as the plant reaches its mature size. Overgrown shrubs are more difficult to successfully prune without accidentally wounding or killing the shrub. Flowering shrubs such as the lilac, rose of Sharon and forsythia should all be pruned at the proper time in order to produce new flowers in the subsequent growth year.

Things You'll Need

• Pruning shears
• Branch loppers
• Pruning saw
• Sharpening stone
• Gloves
• Bleach
• Clean cloth

Instructions

1. Prune spring-flowering shrubs such as lilac or forsythia after they blossom. Spring-flowering shrubs produce new flowers on growth that is one year old. If you prune spring-flowering shrubs in late winter before they bloom, you will prune away blooms. Prune summer-blooming ornamentals such as rose of Sharon in late winter. Rose of Sharon and other summer-blooming shrubs like it will produce blooms on new growth that appears in spring.

2. Sharpen your pruning tools before pruning to avoid injuring flowering shrubs. To hone the instrument, hold the tool so that the blade faces away from you. Draw a sharpening stone down the length of the blade.

3. Mix a solution containing 1 part bleach and 9 parts water. Saturate a clean cloth with this solution and swipe your tool's blades with it. Continue to clean the blades between pruning or after removing diseased branches, to prevent the spread of diseases.

4. Cut all branches at a 45-degree angle to the limb that they adjoin, sloping downward and away from the primary stem.

5. Remove any dead, diseased or broken branches by cutting them off at the point where they join a healthy limb.

6. Cut back long, leggy or overgrown branches by removing the branch just above a point where an exterior-facing leaf and bud emerge. This is called heading back. The branch will sprout a new leader from the bud. Head back the central branches and one-third of each branch from a lilac bush in order to promote circulation in the plant.

7. Thin out long, weak shoots of forsythia by cutting them off at the soil level. Make a cut that is parallel to the ground. Head back remaining long shoots to an outer facing bud.

8. Remove any branches of rose of Sharon that are too closely spaced or that rub together.

References

• University of Kentucky: Pruning Lanscape Shrubs
• Colorado State University: Rose of Sharon
• Iowa State University Extension: Pruning Ornamental Shrubs

Resources

• University of Missouri Extension: Pruning Ornamental Shrubs