Thyme: Indoor Sow and Potted Plant Herb
How to Sow and Plant
Thyme may be grown from seed sown early indoors or as a potted plant.
Sowing Seed Indoors:
- Sow thyme seeds indoors 6-8 weeks before the last frost in spring using a seed starting kit
- Sow seeds ¼ inches deep in seed-starting formula.
- Keep the soil moist at 70 degrees F
- Seedlings emerge in 14-21 days.
- As soon as seedlings emerge, provide plenty of light on a sunny windowsill or grow seedlings 3-4 inches beneath fluorescent plant lights turned on 16 hours per day, off for 8 hours at night. Raise the lights as the plants grow taller. Incandescent bulbs will not work for this process because they will get too hot. Most plants require a dark period to grow, do not leave lights on for 24 hours.
- Seedlings do not need much fertilizer, feed when they are 3-4 weeks old using a starter solution (half strength of a complete indoor houseplant food) according to manufacturer’s directions.
- If you are growing in small cells, you may need to transplant the seedlings to 3 or 4 inch pots when seedlings have at least 2 pairs of leaves before transplanting to the garden so they have enough room to develop strong roots.
- Before planting in the garden, seedling plants need to be “hardened off”. Accustom young plants to outdoor conditions by moving them to a sheltered place outside for a week. Be sure to protect them from wind and hot sun at first. If frost threatens at night, cover or bring containers indoors, then take them out again in the morning. This hardening off process toughens the plant’s cell structure and reduces transplant shock and scalding.
Planting in the Garden:
- Select a location in full sun with well-drained soil.
- Prepare the bed by turning the soil under to a depth of 8 inches. Level with a rake to remove clumps of grass and stones.
- Dig a hole for each plant large enough to amply accommodate the root ball.
- Carefully remove the plant from its pot and gently loosen the root ball with your hands to encourage good root development.
- Set the plants 12 inches apart.
- Place the top of the root ball even with the level of the surrounding soil. Fill with soil to the top of the root ball. Press soil down firmly with your hand.
- Use the plant tag as a location marker.
- Thoroughly water and apply a light mulch layer on top of the soil (1-2 inches) to conserve water and reduce weeds.
How to Grow
- Keep weeds under control during the growing season. Weeds compete with plants for water, space and nutrients, so control them by either cultivating often or use a mulch to prevent their seeds from germinating.
- Mulches also help retain soil moisture and maintain even soil temperatures. For herbs, an organic mulch of aged bark or shredded leaves lends a natural look to the bed and will improve the soil as it breaks down in time. Always keep mulches off a plant’s stems to prevent possible rot.
- Keep plants well-watered during the growing season, especially during dry spells. Plants need about 1 inch of rain per week during the growing season. Use a rain gauge to check to see if you need to add water. It’s best to water with a drip or trickle system that delivers water at low pressure at the soil level. If you water with overhead sprinklers, water early in the day so the foliage has time to dry off before evening, to minimize disease problems. Keep the soil moist but not saturated.
- The lifespan of thyme plants averages about 5-6 years. If you notice the plants are beginning to deteriorate, prune the existing plants back hard to rejuvenate them.
- Monitor for pests and diseases. Check with your local Cooperative Extension Service for pest controls recommended for your area.
Harvest and Preserving Tips
- Harvest sprigs of leaves as needed through the season. Thyme may be used fresh or dried.
- To dry leaves, cut whole stems on a sunny morning. Tie stems loosely in small bunches and hang in a dry, airy location out of the sun. OR spread on a cheesecloth or a window screen in a dry, shady location. OR dry herbs in the oven for 2-3 hours on a cookie sheet at the lowest heat, leaving the oven door open. OR use a dehydrator following the manufacturer’s instructions. When thoroughly dry, store in a tightly sealed container in a dry, dark location such as a cupboard.
- Thyme may also be frozen in ice cube trays in water or olive oil. Remove the leaves from stems first.
- Thyme may also be added to vinegars, herb butters and used to infuse honey.
Common Disease Problems
Alternaria Leaf Spot: Small, round reddish brown spots with white to gray centers form on the upper surface of the leaves. The lesions may encircle the stems and cause wilt. This disease is worse in warm, wet or very humid weather. Burpee Recommends: Avoid getting water on the foliage. Remove infected plant parts and do not work around wet plants. Provide plenty of air circulation. Contact your Cooperative Extension Service for fungicide recommendations.
Botrytis: This fungus causes a grey mold on flowers, leaves, stems and buds. It thrives in cool wet weather conditions. Burpee Recommends: Remove affected plant parts, avoid watering at night and getting water on the plant when watering. Make sure plants have good air circulation. Contact your Cooperative Extension Service for fungicide recommendations.
Damping Off: This is one of the most common problems when starting plants from seed. The seedling emerges and appears healthy; then it suddenly wilts and dies for no obvious reason. Damping off is caused by a fungus that is active when there is abundant moisture and soils and air temperatures are above 68 degrees F. Typically, this indicates that the soil is too wet or contains high amounts of nitrogen fertilizer. Burpee Recommends: Keep seedlings moist but do not overwater; avoid over-fertilizing your seedlings; thin out seedlings to avoid overcrowding; make sure the plants are getting good air circulation; if you plant in containers, thoroughly wash them in soapy water and rinse in a ten per cent bleach solution after use.
Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Contact your Cooperative Extension Service for fungicide recommendations.
Root Rots: A number of pathogens cause root rots of seedlings as well as mature roots. Burpee Recommends: Pull up and discard infected plants. Make sure your soil has excellent drainage. Contact your Cooperative Extension Service for recommendations.
Common Pest and Cultural Problems
Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps which feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.
Deer: Plants may be eaten to the ground. Burpee Recommends: Try a deer repellent or physical barrier for young plants.
Mealybugs: Mealy bugs are 1/8 to ¼ inch long flat wingless insects that secrete a white powder that forms a waxy shell that protects them. They form cottony looking masses on stems, branches and leaves. They suck the juices from leaves and stems and cause weak growth. They also attract ants with the honeydew they excrete, and the honeydew can grow a black sooty mold on it as well. Burpee Recommends: Wash infected plant parts under the faucet and try to rub the bugs off. They may also be controlled by predator insects such as lacewings, ladybugs and parasitic wasps. Check with your Cooperative Extension Service for pesticide recommendations.
Spider Mites: These tiny spider-like pests are about the size of a grain of pepper. They may be red, black, brown or yellow. They suck on the plant juices removing chlorophyll and injecting toxins which cause white dots on the foliage. There is often webbing visible on the plant. They cause the foliage to turn yellow and become dry and stippled. They multiply quickly and thrive in dry conditions. Burpee Recommends: Spider mites may be controlled with a forceful spray every other day. Try hot pepper wax or insecticidal soap. Check with your Cooperative Extension Service for miticide recommendations.
Whitefly: These are small white flying insects that often rise up in a cloud when plants are disturbed or brushed against. Burpee Recommends: They are difficult to control without chemicals. Try hot pepper wax or insecticidal soap. Check with your Cooperative Extension Service for pesticide recommendations.
Thyme FAQs
Can I grow thyme indoors? Yes, thyme is fine grown indoors in a sunny location.
How can I use thyme as a companion plant? Plant thyme near members of the cabbage family to deter insects that attack those plants. Thyme also may be planted as a companion to eggplant, onion, potato, sage and tomato, improving the flavor and vigor and deterring insects.
My thyme is getting woody, how can I rejuvenate it? Cut out any dead or damaged stems in late winter or early spring. In summer, trim the plant back by one third of its height if it looks leggy. Cut back overgrown stems to the desired height to keep a mounded shape.
Are thyme flowers edible? Yes thyme flowers are edible and may be scattered on salads, or added to teas.
How can I make a thyme topiary? Prune the side shoots to encourage vertical growth. Stake the plant and hold it to the stake with soft ties. Let it grow in full sun with plenty of water and when the plant is about 2 feet tall, snip the tops to encourage side shoots. Strip the bottom two thirds of the stem of the branches and leave the top third for shaping. Continue to pinch off the growing tips to maintain a full dense top.