Tender annual herbs, like basil, dill, and cilantro, don't need to be pruned. Instead, these plants do best when trimmed back during harvest season, which sometimes amounts to only a matter of weeks. However, perennial herbs, like lavender, oregano, sage, thyme, and rosemary, develop woody stems and need some type of seasonal maintenance pruning. When left to their own devices and with proper growing conditions, perennial herbs may become shrubs or carpets of ground cover. And, any plant that is allowed to grow leggy will eventually split open and 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 and enhances the herb's flavor.
When to Prune
Harvesting herbs can be done anytime during the growing season, but the act of pinching off tender new growth is much different than actually pruning the plant. Pruning, or cutting back old growth, is best done in the early spring once new growth starts to form at the base of the plant. A second pruning can be done 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.
Don’t prune too late in the season, though. Encouraging new growth at this time will thwart the plant's effort of segue into winter dormancy. Also, tender new leaves can be killed by frost, resulting in a stressed and weakened plant.
What You'll Need
- Pruning shears
- Gardening gloves
- Kitchen scissors
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 summer.
- Working Time: Up to one hour
- Total Time: Up to 3 months
- 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—like germander, marjoram, oregano, and winter savory—by half to get rid of old foliage that was not harvested in the prior year.
- 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 may need regular harvesting every few days in the middle of the summer.
- Go big and harvest 1 to 2 inches of the plant's stem to allow it to grow two separate branches, creating more foliage and training its shape.
- 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
Lavender plants need special treatment if you are growing them for ornamental appeal. You don't want to lop them off across the top or you will get an unnatural look. Instead, follow specific lavender pruning methods to keep them fragrant and attractive, and to help them better survive winter conditions.
- Working Time: Up to 2 hours
- Total Time: Several years
- Regularly pinch off some of the new growth on any young lavender plant to force it to establish a strong root system and throw out subsequent branches.
- After the first flowers show, cut the shoots 2 to 3 inches up from the woody base and just underneath the flowers.
- Deadhead everblooming varieties throughout the summer by cutting them back to the first set of leaves. Dry the leaves to make body products or use them in culinary dishes.
- After the blooms have faded, shape the plant by pruning it into a mound. Doing so each consecutive year will yield a large, ornamental (and fragrant) addition to your perennial garden.
- Discontinue pruning efforts in late August, as cutting the plant after this time can weaken it enough so that it won't survive the winter.
Herb Pruning Tips
Even if your woody herbs don't look like they need trimming in the spring, still cut the stems back to the new growth, but don't remove more than the top third of each stem.
Larger herbs, like 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 them back by up to one-third.
With proper annual pruning, your lavender bush should display more green growth and flowers and have less of a woody "trunk." However, some varieties, like French, Spanish, or woody lavender, are non-hardy and require only gentle trimming. Pruning these varieties in a similar fashion to the hardier ones may result in dead plants.
While lavender flowers are most often dried and used to freshen up a room or to make body care products, you can also use lavender as a culinary herb to add spice to grilled chicken or steak or to put a twist on a traditional summer marinara sauce.