Most commonly used herbs will grow in the Northeast. If you have room, you can make herbs part of your vegetable garden. However, you may prefer to grow herbs in a separate area, particularly the perennials.
Herb Garden Size
First, decide on the size of your herb garden; this will depend on the amount of variety you want. Generally, a kitchen garden can be an area 20 by 4 feet. Individual 12- by 18-inch plots within the area should be adequate for separate herbs. You might like to grow some of the more colorful and frequently used herbs, such as parsley and purple basil, as border plants. Keep annual and perennial herbs separate. A diagram of the area and labels for the plants also will help.
Site and Soil Conditions
When selecting the site for your herb garden, consider drainage and soil fertility. Drainage is probably the most important single factor in successful herb growing. None of the herbs will grow in wet soils. If the garden area is poorly drained, you will have to modify the soil for any chance of success. To improve drainage at the garden site, remove the soil to a depth of 15 to 18 inches. Place a 3-inch layer of crushed stone or similar material on the bottom of the excavated site. Before returning the soil to the bed area, mix some compost or sphagnum peat and sand with it to lighten the texture. Then, refill the beds higher than the original level to allow for settling of the soil.
The soil at the site does not have to be especially fertile, so little fertilizer should be used. Generally, the highly fertile soil tends to produce excessive amounts of foliage with poor flavor. Plants, such as chervil, fennel, lovage, and summer savory, require moderate amounts of fertilizer. Adding several bushels of peat or compost per 100 square feet of garden area will help improve soil condition and retain needed moisture.
Sowing Herb Seed
Nearly all herbs can be grown from seed. Although rust infects mints, very few diseases or insects attack herbs. In hot, dry weather, red spider mites may be found on low-growing plants. Aphids may attack anise, caraway, dill, and fennel.
A few herbs, such as mints, need to be contained or they will overtake a garden. Plant them in a no. 10 can or bucket; punch several holes just above the bottom rim to allow for drainage. A drain tile, clay pot, or cement block also can be used. Sink these into the ground; this should confine the plants for several years.
Herbs can also be grown in containers, window boxes, or hanging baskets. These methods will require more care, especially watering. If possible, sow seeds in shallow boxes in late winter. Transplant seedlings outdoors in the spring. A light, well-drained soil is best for starting the seedlings indoors. Be careful not to cover the seeds too deeply with soil. Generally, the finer the seed, the shallower it should be sown. Sow anise, coriander, dill, and fennel directly in the garden since they do not transplant well.
Most biennials should be sown in late spring directly into the ground. Work the soil surface to a fine texture and wet it slightly. Sow the seeds in very shallow rows and firm the soil over them. Do not sow the seeds too deeply. Fine seeds, such as marjoram, savory, or thyme, will spread more evenly if you mix them with sand. Some of the larger seeds can be covered by as much as one-eighth of an inch of soil. With fine seeds, cover the bed with wet burlap or paper to keep the soil moist during germination. Water with a fine spray to prevent washing away of the soil.
Cutting and Division
Cutting and division also are useful in propagating certain herbs. When seeds are slow to germinate, cuttings may be the answer. Some herbs, however, spread rapidly enough to make division a main source of propagation. Tarragon, chives, and mint should be divided while lavender should be cut.
Fresh leaves may be picked as soon as the plant has enough foliage to maintain growth. To ensure good oil content, pick leaves or seeds after dew has disappeared but before the sun becomes too hot. For dry, winter use, harvest leaves before the flower buds open. Pick the seed heads as the color changes from green to brown or gray. Wash dirty leaves and seed heads in cold water; drain thoroughly before drying.
Perennial and biennial herbs should be winter protected. Many herbs are shallow-rooted, which makes them susceptible to heaving during spring thaws. Mulch with straw, oak leaves, or evergreen boughs 4 inches deep to protect the plants. Apply the mulch after the ground has frozen in early winter. Do not remove the mulch until plants show signs of growth in early spring. Early removal could result in some early frost damage.