Herbs typically require minimal maintenance, although taking periodic cuttings and pruning the plant help encourage healthy, vigorous growth while keeping the plant's size in check. The keys to successful pruning include choosing the right tool for the job and cutting the plant to enhance its natural shape. This simple, basic process typically takes just a few minutes, but can extend your growing season to give you a more bountiful harvest.
The type of pruning tool you need to use depends on the size of the branches you intend to trim. For example, herbs with slender stems, such as basil (Ocimum basilicum), may only need a sharp, clean pair of kitchen shears to prune and pinch. To trim woodier, taller-growing herbs such rosemary (Rosmarinus officinalis), use a pair of sharp pruning shears. Pruning shears are ideal for trimming branches with a diameter of 3/4 inch or less. Any branches larger than that should be pruned with lopping shears to avoid jagged cuts and potential damage.
To avoid spreading disease that can damage your herbs, always start with clean, sharp pruning tools. To disinfect your tools, brush them clean to remove dirt and debris before soaking the tools in a disinfecting solution. Soak the tool for at least five minutes before rinsing it and letting it air dry. Some effective disinfecting solutions include:
- 1 part bleach mixed with 3 parts water
- 1 part pine oil cleaner mixed with 3 parts water
- Equal amounts of 70 percent isopropyl rubbing alcohol and water
- Full-strength household spray disinfectant
Types of Pruning
Many gardeners grow herbs as annuals, although some can be grown as perennials. For example, rosemary is hardy in U.S. Department of Agriculture plant hardiness zones 6 through 9, and mint (Mentha) is generally hardy in USDA zones 3 through 8. Annuals typically only need pinching to help stimulate growth and prevent the herb from flowering and going to seed. Perennial herbs may also need pruning in the spring to shape the plant and remove any dead material or broken stems and branches. Harvesting the herbs for use in the kitchen or in floral arrangements is another type of pruning.
How to Trim Herbs
Although the placement of the cutting may differ depending on the type of pruning you're doing, the basic process is essentially the same whether you're pruning to shape a perennial herb in spring, or if you're pinching the tips off your basil plant during the growing season. When you harvest herbs, the Herb Society of America recommends doing so just after the dew dries on a sunny morning.
Step 1: Examine the Plant
Take a good look at the herb, noting any damaged branches or stems and examining it for signs of buds or flowers.
Step 2: Remove Damaged Foliage
Prune the affected foliage if you see signs of disease or extensive insect damage. Pruning the affected foliage and disposing of it can be an important step to rectifying the problem and regaining the plant's health.
Step 3: Make Cuts to Stimulate Growth
Place your pruning tool right above the leaf node or branch where you wish to force the herb to produce new growth and cut the stem at a 45-degree angle. To pinch the herb -- which prevents it from going to seed and helps encourage the plant to develop a bushier structure -- snip off several tips ranging from 2 to 4 inches in length.
Mother Earth Living recommends using the plant's existing shape as a guide while you're pruning it. Maintaining the same basic form prevents you from ending up with a flat-topped or misshapen plant.
Step 4: Remove Flowers
Trim away any buds or blossoms from the herb. Once the flowers are allowed to bloom, the the plant starts channeling its energy into producing seeds instead of producing secondary buds and additional foliage.