Growing, Harvesting, and Preserving Herbs
Herbs are easy to grow and rarely damaged by diseases or insects. A few short rows in a vegetable or flower garden will provide an adequate supply of herbs for the average family. Herbs are easily preserved and stored up to a year for future use.
Herbs are either annual, biennial, or perennial. Keep this in mind when locating them in the garden. Group herbs according to light and watering requirements. Most herbs prefer a location with four to six hours of sun, well-drained soil, and a pH around 6.0 to 7.0.
Site perennial herbs in an area that will not be disturbed by tilling. Herbs that spread by runners, such as mints, should be contained in pots when planted directly in the garden. Sink pots in the ground, keeping the top 2 inches of the container above the soil. This will allow runners to be removed before they root in the garden.
Propagation and Cultivation
Herbs may be started either indoors or out. For small seeds, the easiest method is to sow them about six weeks before the average last frost date into containers filled with seed-starting mix. Use peat pots for plants with taproots, such as parsley, dill, and cilantro. Cover seeds with a thin layer of moist seed-starting mix, vermiculite, or milled sphagnum moss. Thin seedlings to four or five per pot. Larger seeds may also be started in individual pots and then thinned to one plant. Keep the soil surface moist until plants are established.
Some herbs are best propagated by cuttings, such as rosemary and sweet bay. Root cuttings in a 3-inch plastic pot or other suitable container with drainage holes. A perlite/vermiculite mix makes a satisfactory rooting medium. Keep the rooting medium moist and cover the pot with plastic to maintain high humidity. Place plants out of direct sunlight when young to prevent wilting. After rooting, transplant the cuttings into soil.
Plant annual herbs outdoors after the danger of frost has passed. Manage weeds during the growing season to prevent competition for water and nutrients. A 1-inch layer of organic mulch will conserve soil moisture and help control weeds.
Watering herbs is best done in the early morning hours. If watering when the temperature is cooler, the water will efficiently reach the root system of the plants. Water deeply to encourage root growth. Irrigation may be necessary during periods of drought; though once established, many herbs are highly resistant to drought.
Harvesting
Harvest herbs regularly during the growing season once the plant has enough foliage to maintain continued growth. Cut sprigs of herbs just above a leaf cluster or, in the case of parsley and chives, at the bottom of the stem. Remove dead or damaged leaves and wipe off dirt that may be present. If the leaves are very dirty, spray them with a garden hose the day before harvesting. Pick the herbs early in the day, as the sun’s heat will pull flavorful oils from the plant.
Most herbs used for drying should be picked just before the flowers open, when the leaves have the highest content of aromatic, volatile oils. Discontinue harvesting leaves of perennials by late summer to allow the plants to store enough carbohydrates to overwinter.
Seeds may be saved for culinary uses or starting plants. Harvest seeds when they change color from green to brown or gray and allow them to dry thoroughly before storing.
Preserving and Storing
Gently rinse and dry leaves for immediate use. Store extras unwashed in unsealed plastic bags in the refrigerator crisper and wash before use.
Herbs can be dried by several methods for future use.
- Air-dry small bunches by stripping leaves from the bottom 2 inches of the stem. Secure the stems with a rubber band because they will shrink during drying. Hang the bunches in a well-ventilated, dust-free, dark area. Label each bunch—dried herbs often look the same. Best results are obtained when leaves dry rapidly without artificial heat or exposure to sunlight. In the case of thick, succulent leaves, such as those of basil, rapid drying in a warm oven, dehydrator, or solar dryer may be the only method of retaining color and oils.
- If the leaves are not too small, they may be removed from the stems and dried in a single layer on trays made of window screening or 1-inch-mesh hardware cloth (should be food grade). Stir the leaves gently once or twice a day to speed the drying process. Note that the screening should be food grade. Some older screens are a metal that is reactive.
- Drying may be accomplished in the oven at low heat (110°F or lower) by leaving the oven door slightly ajar. Spread the leaves on a cookie sheet and stir occasionally.
- When drying a large quantity of herbs, a dehydrator is a good choice. Preheat the dehydrator with the thermostat set between 95 and 115°F. Place the herbs in a single layer on the dehydrator tray so they are not touching or overlapping. If needed, cover the dehydrator tray with a fine, food-grade plastic screen to prevent herbs from falling to the bottom. To allow space for the larger leaves, remove some of the trays. For best flavor, dry herbs on the lowest setting possible. If the dehydrator does not have a thermostat option, use the shortest time possible. When drying roots, cut them into ¼- to ½-inch pieces. The drying time for roots is six to ten hours; they will be stiff when they are completely dry.
- Herb leaves are dry when they become brittle and crumble into powder when rubbed between the hands. For a powdered or ground form, crush the leaves with a rolling pin, pass them through a fine sieve, or grind them in a blender or with a mortar and pestle. To preserve flavor, store the leaves whole and crush when ready to add to food.
- Store dried herbs in airtight containers in a cool, dry place out of direct sunlight. Stored correctly, the herbs will retain their essential oils and flavors for up to one year. Several methods exist for freezing herbs. Choose the method based on how the herb will be used later in the kitchen. For details, see the Penn State Extension article Freezing Herbs.
- Fill an ice cube tray with a combination of clean, chopped herbs and either water or oil, depending on later use. Place in the freezer. When frozen, transfer cubes to a freezer-quality bag or jar and return them to the freezer. Always label each jar or bag with the contents and date. Choice of a neutral-flavored canola oil or a more robust olive oil depends on personal taste and what complements the flavor and strength of the herb.
- Spread clean, dry leaves in a single layer on a cookie sheet and place in the freezer. When frozen, place herbs in a labeled freezer bag or jar, working quickly to avoid thawing. Leaves frozen in this manner should not mat together, allowing for easy removal of the amount needed.
- When freezing herbs, sealed glass jars are a better choice in preventing odor transfer than plastic containers.
- A few herbs, such as rosemary, thyme, and dill, freeze well on their stems. Wrap a few stems in plastic wrap and then either over wrap in aluminum foil or place in a freezer bag. Label.
- Freezing will change the structure of herbs, but if done correctly, their flavor will be retained. Thawed dill weed will be darker and limp, but it can be used in pickling. Do not thaw herbs before using them in cooking. Add them directly from freezer to soups and stews or the frying pan. Use frozen herbs within one year.
Growing in Containers and Indoors
Many herbs, such as trailing rosemary, variegated sage, oregano, and chives, can add interest to outdoor containers and are a convenient way to grow herbs when garden space is limited. Use a quality potting soil in containers. Do not use topsoil or garden soil. Be sure the container has drainage holes and do not add stones or broken pottery in the bottom of the pot. Containers dry out quicker than in-ground plantings, so check them often for watering. Most small-sized herb plants can be grown indoors. When grown in a sunny area away from heat sources and drafts, they will supply sprigs for culinary use throughout the winter. Some of the best to try are basil, sweet marjoram, oregano, rosemary, thyme, and parsley. If the container has a saucer, check soon after watering to remove excess water accumulating under the pot.
Uses
Herbs are a healthy way to add flavor to food. When adding herbs to recipes, note that oil concentrations in dried herbs are greater than in fresh. Use 2 tablespoons of fresh for 1 teaspoon of dried herbs. In addition to adding pleasant scents to sachets, herbs are also used in potpourris, candles, soaps, and cosmetics.