Growing herbs

By Aaron J. Steil–Iowa State University Extension and Outreach

AMES, Iowa — Herbs are annuals, biennials, and perennials that die back to the ground each year and are used for their flavor, fragrance, and medicinal properties. These easy-to-grow plants not only provide new and different flavors and aromas to food but can be beautiful additions to the landscape.

What growing conditions do herbs need?

Herbs grow best in the same conditions as most vegetables. Plant in full sun with at least six hours of sunlight a day. While not ideal, some species will grow in part-sun, receiving two to four hours of direct sunlight each day. Herbs will grow well under a wide range of soil conditions, with the exception of extremely wet, poorly drained soils. In general, herbs do better in soils with low to medium fertility, so additional fertilizer applications are not typically needed. Too much fertilizer produces lots of foliage that is low in flavor. 

Perennial herbs should be grown in an area where they will not be disturbed year to year. They overwinter best when soils are well-drained. Some marginally hardy specie, like sage and lavender, sometimes benefit from an extra mulch layer applied just after the soil freezes in November and removed by mid-March.

Learn how to successfully grow herbs in Iowa.

How do I harvest herbs?

Most herbs can be cut and used fresh throughout the growing season. They can also be harvested, dried, and stored for use during the winter months.

Many herbs, such as sage, rosemary, and basil, are grown for their leaves. These herbs should be harvested when their flower buds are just beginning to open. The oils in the leaves, which give each herb its distinctive flavor and aroma, are at their maximum levels at this stage of growth. Remove approximately one-third of the current year’s growth on perennial herbs. Annual herbs can be cut back more severely. Make the cuts on annuals approximately 4 to 6 inches above the soil surface. The annuals can be cut at ground level when harvesting in the fall before the first frost. Most annual and perennial herbs can be harvested in mid-summer and again in the fall.

Herbs should be harvested in the early morning, after the dew has evaporated but before the sun becomes hot. After harvesting, rinse the herbs in cool water. Shake off excess water and place them on paper towels to dry for a few minutes.

How do I dry herbs for later use?

Air drying is the most popular method to dry herbs. To dry whole branches or stems, gather eight to 12 stems in a bunch. Tie the ends of the stems together and hang each bunch upside down in a warm (70 to 80 F), dark, well-ventilated location. The herbs should be dry in two to four weeks. When thoroughly dry, strip the leaves from the plants. Crush or crumble the leaves and store in airtight jars in a cool, dry place.

Some herbs, such as dill, caraway, and coriander, are valued for their seeds. Harvest the seedheads just before they turn brown. Cut off the entire seedhead and place it in a paper bag. Then place the bags in a warm, dry location. After drying, shake the seeds loose in the bag. Remove any chaff by pouring the seeds from one container to another outdoors in a light wind.