Some herbs such as basil, chives, parsley, and dill grow easily from seed. Other simple-to-start varieties include angelica, borage, chamomile, chervil, cilantro, coriander, fennel, lemon balm, marjoram, sage, stevia, thyme, and winter savory. If you start herbs from seeds, follow the planting instructions on the seed packet. The basics are the same whether you start seeds indoors to get a jump on the growing season or plant them directly in the ground.
The best time to plant an herb depends on its cold tolerance and the average last frost date in your area. Sow hardy perennial herb seeds outdoors several weeks before your average last frost date. However, most tender, annual herbs germinate better in warm soil -- so wait until after the average last frost date to plant them.
Plant container-grown herbs in the garden after danger of frost has passed. Dig a hole at least twice as wide as but no deeper than the pot in which the herb is growing. Slide the herb out of its nursery pot. Loosen or slice through any circling roots, then place the root ball into the hole and just barely cover it with soil. Water the root zone well after planting.
Most herbs grow best in well-drained soil and develop their most intense flavor if kept on the dry side. Their water needs depend on soil type, weather conditions, and type of herbs. For example, you'll need to water plants growing in sandy soils more frequently than those in clay. Keep in mind that plants use more water during hot, windy conditions with low humidity than when the weather is cool, humid, and cloudy.
When watering, apply enough water to moisten the root zone at least 6 inches deep. Soaker hoses or drip irrigation systems are efficient ways to apply water: They avoid wasting water by applying it just to the root zone of the plants and prevent disease by keeping the foliage dry.
Herbs that receive high levels of nutrients, particularly nitrogen, produce inferior growth with little flavor or fragrance. For that reason, avoid overfertilizing your herbs. Organic fertilizers, which decompose slowly, and controlled-release manufactured fertilizers are less likely to provide an excess of nutrients at one time. Follow soil test recommendations or label directions to know how much fertilizer to apply.
Test Garden Tip: Never use fresh manure in your herb garden. Compost it first to eliminate the possibility of spreading harmful bacteria onto your herbs.
The most flavorful and succulent part of herbs is the tender new growth. Keep your herb plants lush and bushy by regularly pinching 2-3 inches off the stem tips. This encourages branching and new growth. If you desire more leaves, pinch off any flowers that form. Stop pinching or pruning woody herbs at least eight weeks before the first frost of fall to give the new growth time to harden off before winter.
Prune and clean up dead stems of last year's growth on plants such as lemon balm, mint, artemisia, and tansy, if you didn't cut them back in autumn. Some perennial herbs become woody or lanky after several years in the garden. In spring, prune them back by one-third or to within 4 inches of the ground before new growth begins. This encourages a bushy, more compact form.
Some perennial herbs such as chives form clumps; others such as thyme spread by runners. Both spreading- and clumping-type herbs can be dug and divided in early spring to make new plants.
Propagate woody herbs such as rosemary from stem cuttings. Less woody herbs such as mint, oregano, thyme, and basil will also root easily from cuttings.
Stems of some herbs form roots where they come into contact with the ground. You can help the process along by layering the stems. Bend a flexible stem to the soil, nick the base of it, apply rooting hormone, pin it to the soil, keep moist, and wait several months for roots to form.
Prevent weeds from growing in your herbs by using mulch. Organic mulches such as wood chips, cocoa bean shells, or pine needles are good to use. Apply a layer of mulch 2-4 inches deep, but keep it away from the crown of the herb plant. Mulch smothers weeds, prevents most weed seeds from germinating, and those that do grow are easier to pull. In addition, mulch conserves moisture, so you'll need to water less frequently.