Many herbs are easy to grow from seeds sown directly in your garden, and once established, they will resow themselves freely year after year. Others have very specific germination and growing requirements.
Sowing Seeds Outdoors
Some annual herbs, such as basil, borage, and German chamomile, grow easily from seeds sown directly in the ground outdoors. Others, like caraway, chervil, cilantro, and dill, have sensitive roots, which prompt the plants to bolt — meaning go to seed — if disturbed. To grow these herbs from seeds, start them where they will grow outdoors, or sow the seeds indoors in peat pots, which later can be transplanted to the garden without disturbing the plant roots.
Perennials are generally more difficult to start from seeds, but there are some exceptions: angelica, anise hyssop, chives, fennel, lemon balm, lovage, sage, and summer savory are relatively easy to sow outdoors.
To prepare a garden bed for seeds, remove stones and clumps of soil. Dig in some compost, turn over the soil, and break it up using a hoe, rake, or similar garden tool. For optimal germination, the soil should be finely textured and lightweight. Follow the seed packet instructions for planting depth. If small seeds are planted too deep, they can run out of energy before the sprouts reach the soil surface. Some seeds require light for germination and must be pressed into the soil surface but not covered. Other seeds germinate only in the absence of light and so must be planted deeper: as deep as three or four times their width. Lightly water the seeded bed and keep the soil moist (but not saturated) until the seeds sprout.
Starting Seeds Indoors
To give plants a jump on the growing season, you can germinate seeds indoors before the weather warms and then transplant the seedlings outdoors when conditions are favorable. Seeds can be started in a variety of container types, as long as the container allows excess water to drain out of it. Commercially available “seedling trays” allow seedling roots to draw water from a bottom tray. Some, called plug trays, have thimble-sized soil “plugs” that pop out for easy transplanting.
For best results, germinate seeds in a medium specially formulated for seed starting. Seed-starting mixes are lightweight so that delicate seedling roots can grow easily, and they’re sterile, or free of pathogens, pests, and weeds. You can buy a commercial blend at a garden supply store, or prepare your own seed-starting mix at home by combining 2 parts sand, 2 parts perlite, and 1 part well-aged compost.
Moisten the medium with warm water before filling your seed-starting containers. When sowing seeds, follow the instructions on the seed packets. A general rule is that seeds should be planted no more than three to four times as deep as each seed is wide. Until the seeds germinate, keep the growing mix consistently moist — not too wet or dry — by covering the seedling trays with clear plastic wrap or a plastic dome.
Check the seed packet for the herb seeds’ ideal germination temperature; many (but not all — see “Stratification”) germinate most readily in consistently warm soil. To provide gentle warmth, set your seedling trays atop a heat-generating appliance, such as a refrigerator, or on a seedling germination mat.
Starting herbs from seed is fun, easy, and thrifty. Here’s how to do it.
STEP 1: To start seeds in trays, sprinkle the seeds evenly over the surface of your moistened medium.
STEP 2: Cover the seeds with more planting medium, according to the specifics on the seed packets.
STEP 3: Gently water to moisten the surface. Cover your trays with plastic to retain moisture until the seeds sprout.
When your seeds sprout, move the trays to a spot where they will receive 14 to 16 hours of light each day. Windowsills are not usually bright enough for good seedling growth; instead, use a grow light fixture. Although many types of lights are sold and used for starting seeds and growing plants indoors (including metal halide, high pressure sodium, and LED), a standard fluorescent “shop” light fixture will work just fine for starting seeds. Keep the lights very close to the seedlings — 1 to 3 inches above the leaves is optimal.
When the first true leaves appear above the seed leaves (cotyledons), it’s time to transplant the seedlings into larger containers — pressed peat pots, peat pellets, or cell packs — filled with moistened growing mix. To transplant, first make planting indentations in the growing mix of the larger containers. Use a small fork or craft stick to gently lift out the seedlings with their roots and the surrounding soil. Place the roots in the new planting holes, carefully press down the soil around them, and gently water. Feed the seedlings weekly with an organic fertilizer, such as fish emulsion that’s diluted to half-strength.
After 6 to 8 weeks, when outdoor conditions have stabilized, begin acclimating your indoor seedlings to wind, sun, and varying temperatures. This process, called “hardening off,” encourages the plants’ tender new growth to become more firm and less susceptible to damage. To do this, place seedlings in a shady outdoor location with a temperature between 45° and 50°F. Over the next few days, move the seedling containers into sunlight for increasing periods of time. After 10 days, the seedlings should be hardy enough to plant in your garden.
After seeds sprout, it’s time to move them to a larger container.
Transplanting seedlings requires a delicate touch. Use a small fork or craft stick to gently lift them out, along with their roots.
Special Seed-Starting Techniques
A few herbs require special but very simple seed-starting methods.
Scarification: Scarification simply means “scarring” or nicking the seed coat. It is used to promote the germination of hard seeds, such as those of astragalus. To scarify seeds, use a sharp knife to gently nick the outside of the seed, or rub seeds over a piece of fine sandpaper. Small seeds can be rubbed between two pieces of fine sandpaper.
Stratification: This is a method of chilling seeds to encourage germination, just as the seeds of many plants in nature require a period of chilling before they can germinate — breaking their dormancy by going through cold winter temperatures. Echinacea (Echinacea spp.), gentian (Gentiana lutea), jewelweed (Impatiens capensis), lavender (Lavandula angustifolia), myrrh (Myrrhis odorata), osha (Ligusticum porteri), and sage (Salvia officinalis) seeds respond well to stratification. Put seed packets in a zipper-lock bag (to keep them from drying out), mark the date on the bag, then refrigerate the sealed bag for 4 to 6 weeks, or the recommended period for your specific seeds. Start seeds according to the packet directions.