How to Grow Thyme

If starting thyme from seed, begin the plants indoors in a shallow growing tray about six to eight weeks before the last frost is expected. Use a well-drained tray and do not pack soil too tightly. Keep in full sunlight or under fluorescent grow lights. Thyme grows especially well when exposed to compact fluorescent or high-intensity bulbs suspended two to four feet above the plants. Use an oscillating fan set to low to blow air gently across the thyme seedlings for approximately two hours a day. The breeze will help simulate outdoor growing conditions, encouraging the plants to develop stronger stems and leaves.

Since many varieties of thyme do not grow consistently from seeds, however, you may also wish to start thyme from young plants purchased at a nursery or obtained from a friend or neighbor. Thyme transplants well as long as it is grown from a separated plant rather than a cutting. Separate thyme plants when they are three or more years old.

When planting thyme outdoors, choose an area in full or nearly full sun. Thyme prefers sandy or loamy soil that is well drained. Avoid planting thyme in heavy clay or in areas where water collects, such as the bottom of small slopes or in a hollow in the ground. Thyme prefers a soil pH between 6.5 and 7.0, or neutral to slightly alkaline. However, thyme will grow in soils with a pH of up to 8.5. Thyme does not appreciate acidic soil.

Because young thyme plants grow slowly in their first year or two of life, mulching will be necessary in most outdoor environments to prevent weeds from taking over the thyme bed. Use mulch with grass clippings or a similar organic, pH neutral or slightly alkaline mulch. Mulching mature thyme plants in early October or before first frost will help the plants survive the winter.

Do not fertilize thyme unless the soil is particularly poor or the thyme was started hydroponically, or on water alone. Fertilize thyme lightly no more than once per month. Mature thyme rarely needs to be fertilized unless the soil quality remains poor, but the plants should be mulched regularly.

Water thyme when first planted outdoors and on a regular schedule thereafter, unless it rains. Thyme can tolerate a mild to moderate drought, and it is better not to water thyme enough rather than to water it too much.

Do not trim or harvest thyme for the first two years in order to ensure the plants are firmly established. Once plants are mature, harvest thyme after the first flowering is over, usually in late June or early July. Particularly healthy or mature plants can endure a second harvest at the end of summer after their second flowering has died back. Do not attempt a second harvest until the plants are at least five years old, in order to give the plants a chance to firmly establish themselves in their new home.