Tender annual herbs, including basil and dill, usually don't need to be pruned. Just harvest them as needed. But perennial herbs—such as lavender, oregano, sage, thyme, and rosemary—often develop woody stems and need some seasonal maintenance pruning. When left to their own devices and with proper growing conditions, perennial herbs can become shrubs or carpets of ground cover. They also can grow leggy (or overly stretched) and eventually flop over. Judicious pruning can improve the look and vigor of your herbs while keeping their size and shape in check. Most importantly, pruning spurs tender, new growth that enhances the herb's flavor.
Equipment / Tools
- Pruning shears
- Gardening gloves
- Kitchen scissors
- Mature herbs
Pruning Culinary Herbs
Most perennial herbs used for culinary purposes (as opposed to those grown for ornamental pleasure) can be pruned by simply removing dead growth and then properly harvesting the new growth throughout the growing season.
Remove Dead Stems
In the spring, wait until you see signs of new green growth on your herb plant. Then, remove dead or broken stems and spent flowers with pruning shears.
Cut Back Soft, Woody Herbs
Cut back herbs such as germander, marjoram, oregano, and winter savory—by half in the spring to get rid of old foliage that was not harvested in the prior year.
Prune the Leaves
During the height of harvest season, regularly prune the leaves from the top of the plant by pinching them off with your fingers or using kitchen scissors. Vigorous growers might need regular harvesting every few days in the middle of the summer.
Harvest One to Two Inches of the Plant's Stem
Also during the height of harvest season, harvest 1 to 2 inches of the plant's stem to allow it to grow two separate branches. This helps to create more foliage and train its shape.
Deadhead Your Herb Plant
In late summer, deadhead your herb plant by pinching off old flowers and cutting back spent or shriveled growth. Do so long before cold fall temperatures set in and plant dormancy begins.
Pruning Ornamental Herbs
Herbs often grown for ornamental purposes, such as lavender plants, need special treatment to keep their appeal. You don't want to lop them off across the top, or you will get an unnatural look. Instead, follow specific pruning methods to keep them fragrant and attractive, as well as to help them survive winter conditions.
Pinch New Growth
Regularly pinch off some of the new growth on any young plant to force it to establish a strong root system and throw out more branches.
Cut the Shoots
After the first flowers show, cut the shoots 2 to 3 inches up from the woody base and just underneath the flowers.
Cut Back the Herbs to the First Set of Leaves
Prune everblooming varieties throughout the summer by cutting them back to the first set of leaves. Dry the leaves of fragrant herbs to make body products, or use them in culinary dishes.
Shape the Plant
After the blooms have faded, shape the plant by pruning it into a mound. Doing so each year will yield a large, ornamental addition to your perennial garden.
Discontinue pruning efforts in late August, as cutting the plant after this time can weaken it enough that it won't survive the winter.
Harvesting herbs can be done anytime during the growing season. But the act of pinching off tender new growth is much different from actually pruning the plant.
Pruning, or cutting back old growth, is best in the early spring once new growth starts to form at the base of the plant. A second pruning can occur just after your herb flowers by removing the deadheads and dry, brittle growth. This type of mid-season pruning increases the plant's vigor, as it diverts its energy into growing fresh leaves and expanding its root system.
Even if your woody herbs don't look like they need trimming in the spring, still cut back the stems to the new growth. But don't remove more than the top third of each stem.
Larger herbs, such as rosemary, sage, and thyme, don’t require much additional pruning during the growing season unless they’ve become leggy or overgrown. If that's the case, shape them by pruning back the plant by up to a third. With proper annual pruning, your plant should display more green growth and flowers and have less of a woody "trunk."
Don’t prune too late in the season. Encouraging new growth at this time will thwart the plant's effort to transition into winter dormancy. Also, frost can kill tender new leaves, resulting in a stressed and weakened plant.
Basic Principles of Pruning Woody Plants. University of Georgia Extension