Thyme in Zone 6A — Mountain West

Thyme is a must-have herb for any Mountain West garden. Its earthy flavor elevates everything from roasted meats to hearty stews, and its fragrance perfumes the air. Plus, it thrives in our intense sun and well-drained soil, giving you a satisfying harvest all summer long.

Our short growing season and alkaline soil can present challenges, but with careful planning, you can easily grow thyme. Focus on getting a head start, and you'll have plenty of time within our 153-day growing season to enjoy this versatile herb.

Starting thyme indoors is a good option if you want larger plants sooner, but it’s not essential. Thyme is slow to get going from seed, so this gives it a head start against our short season. If you want to try it, start seeds indoors from late February through mid March.

Use seed trays with a good seed-starting mix. Provide warmth (a heat mat helps) and plenty of light – a grow light is ideal, especially with our late spring starts. Water gently from the bottom to avoid disturbing the tiny seeds and prevent damping-off.

Transplant your thyme seedlings outdoors from early to late May, once the danger of hard frost has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the intense Mountain sun and cooler nights.

Space your thyme plants 8-12 inches apart in a sunny spot with well-drained soil. Honestly, buying thyme starts from a local nursery is a great shortcut. It saves you weeks of waiting and gives you a more established plant ready to take off.

Direct sowing thyme is possible in the Mountain West, especially if you're patient. Sow seeds from early May through early July, once the soil has warmed up. Choose a sunny location with well-drained soil.

Prepare the soil by loosening it and removing any rocks or debris. Sprinkle the tiny seeds on the surface and gently press them into the soil. Keep the soil consistently moist until the seedlings emerge, but avoid overwatering. Space plants 8-12 inches apart once they are established.

Thyme is very drought-tolerant, making it perfect for our dry Mountain climate. Overwatering is a much bigger threat than underwatering. During the growing season, water deeply but infrequently.

In spring, when plants are getting established, water about once a week if we aren't getting rain. In the heat of summer, with our moderate-at-altitude temperatures and low humidity, you might need to water every 5-7 days. Use the finger test: stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. Aim for about ½ inch of water per week.

Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our rare humid spells. Signs of underwatering include wilting or yellowing leaves. Overwatering can lead to root rot, which shows up as mushy, brown stems near the base of the plant. A light mulch of gravel or small stones helps retain moisture without suffocating the plant, and it also helps keep the foliage dry.

Thyme requires minimal pruning. The key is to cut it back lightly after flowering to encourage new growth and prevent it from becoming woody.

After the plant finishes flowering, usually in late summer, cut back the stems by about one-third. Avoid cutting into the old, woody growth, as new growth is unlikely to emerge from there. As the first frost approaches in early October, stop pruning to allow the plant to harden off for winter.

You can start harvesting thyme in early July, about 70 days after planting from seed, and continue harvesting until early October. The best flavor is just before the plant flowers, but you can harvest sprigs anytime you need them.

To harvest, simply snip off stems with scissors or garden shears, leaving at least a few inches of growth on the plant. Strip the leaves from the stems and use them fresh or dry them for later use. Regular harvesting encourages bushier growth and continued production. As the first frost approaches, harvest any remaining thyme and dry it for winter use.

Thyme is relatively problem-free in the Mountain West, but two common issues are root rot from overwatering and, less commonly, fungal diseases.

Root Rot *What it looks like:* The stems near the base of the plant become mushy and brown, and the leaves may turn yellow or wilt. *What causes it:* Root rot is caused by consistently wet soil, which deprives the roots of oxygen. This is especially a problem in heavy clay soils or if thyme is planted in a poorly drained location. *How to fix/prevent it:* Improve drainage by amending the soil with sand or compost. Water less frequently, allowing the soil to dry out between waterings. Ensure that thyme is planted in a sunny location with well-drained soil.

Fungal Diseases *What it looks like:* White or gray powdery mildew on the leaves and stems. *What causes it:* Fungal diseases are rare in our dry climate but can occur during periods of high humidity or after heavy rainfall. *How to fix/prevent it:* Ensure good air circulation around the plants by spacing them adequately. Water at the base of the plant to avoid wetting the foliage. Remove and destroy any infected leaves or stems.

Mountain West Specific Challenges: Our dry climate generally protects thyme from many fungal diseases, but be vigilant about overwatering, especially in spring. Even with our moderate-at-altitude heat, the intense sun can stress plants if they aren't well-established, so provide some afternoon shade during the hottest part of the summer, especially for young transplants.

Thyme makes a great companion plant for many vegetables and herbs in the Mountain West garden. Rosemary, sage, and lavender all share similar growing requirements (full sun, well-drained soil) and can help deter pests. Cabbage and strawberries benefit from thyme's pest-repelling properties. Tomatoes also thrive alongside thyme, as it can improve their flavor and protect them from certain pests.

Avoid planting thyme near mint, as mint is very aggressive and can quickly outcompete thyme for resources. Mint also prefers more moisture than thyme, creating conflicting growing conditions.