Growing Herbs in the Garden

Traditionally, the definition of the term "herb" included any soft-stemmed (herbaceous) plant valued for flavor, fragrance, dye, or medicinal use. However, some of our most popular and frequently used herbs (lavender, Lavandula spp., rosemary, Rosmarinus officinalis, and sage, Salvia officinalis, etc.) have woody stems, so the definition has been expanded. Currently, the definition of an "herb" refers to any herbaceous or woody plant, including annuals, perennials, biennials, shrubs, vines, or trees, valued for flavor, fragrance, dye, decorative, medicinal, cosmetic, economic or industrial, and ornamental properties.   

"Native herbs" are those that occurred naturally in the U.S., prior to the European settlement, and not introduced from other countries/regions. Native herbs include bee balm (Monarda fistulosa), bloodroot (Sanguinaria canadensis), milkweed (Asclepias spp.), spicebush (Lindera benzoin), and witch hazel (Hamamelis virginiana).   

 It is important to know the country of origin when growing herbs, because herbs do well once established in a habitat like their native habitat. For example, Mediterranean herbs such as lavender (Lavandula spp.), oregano (Origanum vulgare), rosemary (Rosmarinus officinalis), sage (Salvia officinalis), and thyme (Thymus vulgaris) thrive in full sun and in well-drained, dry, gravelly soil like that found in their native habitats.   

Ornamental Use in the Landscape

The varying flower and leaf colors, textures, and forms are useful in both a formal (knot) and an informal herb garden. They may also be planted and integrated into vegetable, flower, or rock gardens. In a knot garden, geometric patterns and intricate symmetrical designs are subdivided by low hedges, borders, or edgings made of boxwood, germander, lavender, or santolina. Thyme and sweet woodruff are good groundcovers. Herbs grow well in window boxes, hanging baskets, or containers on the deck or placed throughout the garden. Their nectar-bearing flowers attract bees, butterflies, beneficial insects, and even birds to the garden. Several herbs are host plants for the larvae (caterpillars) of butterflies: milkweeds (Asclepias spp.) for monarch caterpillars, and parsley (Petroselinum crispum), dill (Anethum graveolens), and fennel (Foeniculum vulgare) for black swallowtail and anise swallowtail caterpillars. Herbs can also function as companion plants, attracting beneficial insects and repelling harmful ones in the vegetable garden.

Beginning Gardeners

Beginning gardeners may struggle to decide which herbs to plant, as there are numerous varieties to choose from. Think about how you will use the herbs you grow. Many cookbooks offer information on the uses of various herbs for flavoring. By starting with the most commonly used culinary herbs, you can cultivate a useful and enjoyable garden while learning how to grow herbs and which ones you enjoy using in the kitchen.  

Herbs that offer a good selection of stronger flavors include garlic, oregano, tarragon, thyme, rosemary, and sage. Whereas sweet basil, dill, mint, sweet marjoram, and salad burnet are more delicate and can be used for an accent in a dish. 

It is best to start with a small garden until you become familiar with the culture and care needed to grow and harvest herbs. As your interest and needs grow, you can add more varieties of plants to your garden. Since herbs can be annuals (flower one season and die), biennials (live two seasons, flowering the second season only), or perennials (over-winter, flowering each season once established), keep in mind the length and type of life cycle when selecting herbs to grow. Annuals include anise, basil, chervil, coriander (cilantro), dill, and summer savory, while biennials include caraway and parsley. Examples of perennials are chives, fennel, lovage, marjoram, mint, tarragon, and thyme. 

Many beginners choose starter plants that can be planted out after the danger of frost has passed. When choosing plants, check the label (including the botanical name) to be certain they are the plant you want, as many plants have similar common names but different growing and use properties. Check that the plants are hardy in your USDA Plant Hardiness Zone and that they prefer the conditions in the garden areas in which they will be planted. It is best to get a soil test before planting.  

Outdoor Herb Culture

Many of the most commonly used herbs can be grown outside in the Northeast. If you have room, you can incorporate herbs into your vegetable garden, or you may prefer to grow them in a separate area. Having a small herb garden is a good way to familiarize yourself with the growth habits and forms of different herbs. You can also mix herbs with ornamentals to provide contrast and interest. Dark purple basil, for example, may be planted against a backdrop of tall 'Silver King' artemisia in an ornamental bed.  

Garden Size

The size of your herb garden will depend on the quantity and variety of herbs you want to grow. It will also depend on how much time and effort you are willing to put into your garden, as well as how much space you have. Size and planting pattern can affect the extent of maintenance needed.  

A 20-by-4-foot kitchen garden is generally large enough to grow a variety of herbs. Individual 1-by-4-foot rows within the area should provide adequate space for most herbs. The number of plants that will fit into this space depends on the type of plant. About 6 chive plants, or a tight grouping of 10 to 12 plants, will fit in a 1-by-4-foot row, but herbs such as borage, dill, basil, fennel, and summer savory will need more space. Plants that are wide, such as sage, or those that spread on top of the ground, such as the mints, would be quite confined in a 1-foot row. They may need to be thinned or pinched to fit into such a small space.  

 By experimenting with different herbs, you will become familiar with their heights, widths, and space requirements. Then you can create your own designs or patterns, or adapt more detailed designs found in books and periodicals. You might like to grow some of the more colorful and frequently used herbs, such as parsley and purple basil, as border plants. Although it is unnecessary, some gardeners prefer to keep annual and perennial herbs separate to make it easier to replant the annual areas each spring. Annuals that re-seed readily could be given a space of their own to allow for this natural cycle of propagation. Making a diagram of the garden area and labeling the plants will help you to remember what herbs were planted the previous year.  

Planting Herbs in the Garden 

Seedlings planted in the garden should be kept moist until they are established. While some herbs can tolerate drought conditions, none can do so without a well-established root system. To increase transplant success, gradually acclimate seedlings to outdoor conditions and watch for signs of damping-off or wilt soon after transplanting. For seeds sown directly into the garden, initial care is important. Keep seeded areas evenly moist but not wet. Do not allow the soil to become either waterlogged or too dry.  

 A few herbs, such as mints, need to be contained or they will take over neighboring garden plots. One solution is to plant these aggressive herbs in 3- to 5-gallon pots with drainage holes or with the bottom removed, then bury the potted plant in the garden. The rim should protrude an inch or so out of the ground to prevent above-ground runners from quickly spreading. Prune creeping stems so they do not run into neighboring plots and take root. These sunken pots should help confine the plants for a few years.  

Cultivation and Care

Very few diseases or insects attack herbs, but rust infects mints. In hot, dry weather, red spider mites may be found on low-growing plants. Also, aphids may attack anise, caraway, dill, and fennel, while Japanese beetles like basil, borage, and sorrel.  

Most herbs require little care, but to prolong their usefulness, pinch flowers as they appear at the bud stage. Plants, such as basil and mint, can be pinched as they grow for fuller growth. Picking off spent flowers is a choice. Pollinators frequent herb flowers. The flowers of many herbs can also be harvested for their fragrance, beauty, or culinary use before they fade. Because dead leaves and stems left on the plant can attract pests and promote mold growth, it is best to prune dying or dead foliage.  

It is important to control weeds because they compete for moisture and nutrients and may pass diseases, such as viruses, to your garden plants. Lay down a layer of organic mulch (about 3 to 4 inches thick) to keep out weeds and help retain soil moisture.  

 Once established, herbs generally can tolerate adverse conditions. Irrigate them as needed during prolonged dry periods. If wilt is noted, then water as soon as possible. If the garden stays too wet, however, disease problems can occur, so make sure drainage is adequate when planning the garden. Most herb gardens are easy to care for and require mainly weeding and occasional watering.  

Winter Protection

Perennial and biennial herbs should be protected in winter. Many herbs are shallow-rooted, making them susceptible to heaving during spring thaws. Mulch with straw, oak leaves, or evergreen boughs to a depth of 4 inches 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.