Nearly all plants can benefit from pruning. While normally associated with trees, this process can improve both vigor and production for many herbs as well. Pruning naturally stimulates plant growth and gives the gardener the chance to control production, plant growth, and shape.
Most gardeners prune new plants in mid- to late-spring and often naturally prune while harvesting throughout the year for leafy herbs.
How And Which Herbs to Prune
Almost all herbs can benefit from pruning. Most ground cover type herbs will generally be pruned as they are harvested. Any herb with stems and tall plant size, especially those meant for seed harvest, will benefit the most from early pruning.
In the early spring, control plant growth in an upward direction by pinching off the new shoots as they appear on the lower portions of the plant. This encourages top foliage and taller growth, which in turn usually leads to a larger, fuller plant later in the year. By controlling the lower stems, you stop the plant from growing outwards in the beginning and force it instead to go up before it goes out.
Thicker plants and plants that are being pruned later in the spring may require cutting rather than pinching. All unwanted growth should be removed, but leave at least half of the plant intact so you do not harm it before it really gets going. Additionally, plants should never to pruned heavily after the summer if they are to overwinter intact. Doing so may cause early shoots to appear and then be killed with the frost, harming the plant and possibly killing it as well.
In mid-spring, if the plant is being grown for seeds (e.g. dill), pruning can direct the plant’s energy towards specific seed stalks and pods. Do not prune away many leaves. This can distract the plant into growing more to replace them, reducing seed growth. Instead, focus on pruning away late-emerging seed shoots so the plant focuses on those it began earlier, making them larger and with more seed.
Dead heading is a common term for this sort of seed and flower control. Pinching or cutting off seed stalks and buds that are emerging late is recommended for all seed-bearing plants.
Perennials that are harvested at the end of the season can usually be cut all the way down. This “mowing” of the plant allows it to stay dormant over winter and re-sprout in the spring. Cover the leftover exposed stalk with mulch at 3-4 inches to keep it insulated. This practice is most common with heavy wooded herbs rather than softer plants.
Using the Pinched Herb Tips
Some herb tips and branches that are pinched off can be dried or incorporated into cooking. They will have a much milder flavor than the full-grown herb, but need not be wasted just for being taken early. If the stem pinched off is long enough, it may also be rooted to grow a new plant. Cuttings are better suited for this than those pinched off, however.
Herb tips that have been pinched can also, of course, be composted or even dropped to the soil beneath the plant as additive to the mulch and soil already there. So long as they are not diseased, these tips will add to the soil.