Just as you harvest different herbs at different times, you collect different parts of your herbs — leaves, stems, flowers, fruits, seeds, and roots — at different times. The timing of your harvest also depends on how you expect to use the herb: to make tea, for example, or to make a wreath or a nosegay. Annuals, biennials, and perennials have their own quirks, but the rules for harvesting are pretty simple and straightforward.
Follow these tips when harvesting herbs:
Harvesting leaves: Collect foliage when it’s still tender. If you want herb leaves to use as greens in salads, harvest as soon as the leaves are large enough to be used. Harvest in late morning, after dew has dissipated, but before the day has started to heat up. The oils that make herbs taste and smell wonderful and work medicinally are at their most powerful then.
Harvesting seeds: Seeds are the real reason to grow some herbs, such as anise and caraway. With others, such as coriander/cilantro and dill, they’re a bonus for the spice rack. In either case, you don’t want to let seeds get away. Seeds begin forming when pollinated flowers drop away. The seeds are ripe and ready for collecting when they turn from green to brown or black. Watch, too, for seed pods to swell or change color. Shake the ripened flower head into a paper bag, and the seeds will fall into the bag. Be sure to label the bag with the name of the plant and the date you gathered the seed.
Harvesting flowers: For most uses, harvest herb flowers just as they start to open. As with the rest of the plant, their freshness peaks and falls off quickly. Essential oils that provide flavor, fragrance, and healing qualities are all at their acme as the bud is swelling. Cut the flower off with a bit of stem (which helps keep flowers from falling apart) above the top set of leaves.
For dry arrangements, wreaths, or crafts in which you use entire flowers, you achieve a more natural-looking result if you pick flowers at different stages — unopened, partially opened, completely opened. Harvest them with at least 6 inches (15cm) of stem. Potpourri, too, has a more interesting texture if you include a few tight buds along with petals. If you’re going to press flowers, let them open a bit more before you cut them — enough that you don’t have to wrestle them to lay flat. After they’ve fully opened, don’t leave them in the garden, where their color will fade, or where insects can damage them.
Harvesting roots: The ideal time to harvest roots and rhizomes is in fall, after the foliage has died back. That’s when roots are at their most potent. (If you forget, you can harvest the next spring before growth starts, but you may have a harder time finding the plant. In addition, the roots may be more full of moisture and take longer to dry.)
Here are a couple of rules for the underground harvester:
Be patient with roots. Don’t harvest perennials before the autumn of their second year. (A couple of exceptions among culinary roots are chicory, which you can harvest the first year before it goes to seed, and marsh mallow, which is better when harvested in the fall of its third year.) Biennials, such as angelica, begin wearing out and become woody in their second year, so harvest them in their first fall or second spring.
Dig roots when the earth is damp but not sopping wet. Use a spading fork (which is less likely to damage the roots) and delve deep. Cut off the plant tops; if you can’t use them, add them to the compost pile. Roots, unlike herb leaves, need washing after harvesting; if necessary, scrub them with a brush to remove dirt. In most cases, gardeners dig the entire plant when they harvest roots. But if you want that perennial in the same spot next year, remember to slice off a hefty section of root containing an eye, or bud, and replant it.
