Thyme in Zone 6A — Midwest

Thyme is a fantastic addition to any Midwest garden. Its aromatic leaves add depth to everything from roasted vegetables to hearty stews, and the plant itself is a beautiful, low-growing ground cover. Plus, the satisfaction of snipping fresh herbs from your own backyard, especially after a long winter, is hard to beat.

Our Midwest weather can be unpredictable, with variable springs and summer heat spells. But don't worry, with a little planning, you can easily grow thyme within our 178-day growing season. Knowing when to plant and how to care for it makes all the difference.

Starting thyme indoors gives you a head start, although it's not strictly necessary. It makes sense if you want a larger, more established plant sooner. Start your seeds indoors from mid February through early March, about eight weeks before you plan to transplant them outside.

Use seed trays with a good seed-starting mix. Keep the soil consistently moist, and consider bottom watering to prevent damping off. A warm location and grow lights will help germination and early growth, especially since our springs here in the Midwest can be moderate-to-late.

Transplant your thyme seedlings outdoors from mid April through mid May, after the danger of hard frost has passed. Remember to harden off your seedlings for about a week before transplanting, gradually exposing them to outdoor conditions. This helps them adjust to the Midwest weather.

Space your thyme plants 8-12 inches apart in a sunny spot with well-drained soil. Keep an eye on the weather forecast; we sometimes get unexpected cold snaps this time of year. Honestly, buying established thyme plants from a local nursery is a great option here. It skips the slow seedling phase and gets you harvesting much faster.

Direct sowing thyme is definitely an option, particularly if you're patient. Sow seeds from mid April through late July. The soil needs to be workable and ideally around 70°F for best germination.

Prepare the soil by loosening it and removing any weeds. Scatter the tiny seeds on the surface and gently press them into the soil. Keep the area consistently moist until the seedlings emerge. Thin the seedlings to 8-12 inches apart once they're a few inches tall. Direct sowing is simple, but thyme grows slowly from seed, so it takes longer to establish.

Thyme is very drought-tolerant, which is a good thing because overwatering is its enemy, especially with our wet-summer rainfall here in the Midwest. Established thyme actually thrives on neglect. Let the soil dry out between waterings.

During the active growing season, from late spring through summer, water only when the top 2 inches of soil feel dry to the touch. This is the "finger test". Usually, an inch of water per week, including rainfall, is plenty. Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our moderate-to-humid environment.

Signs of underwatering include wilting or yellowing leaves. Overwatering leads to yellowing leaves and potentially root rot. A light layer of mulch around the base of the plant helps retain moisture without suffocating the roots, but don't overdo it, especially with our humidity.

Thyme requires minimal pruning. The key is to avoid letting it get too woody. After flowering, usually in mid-summer, cut back the stems by about one-third.

This encourages new growth and keeps the plant compact. Be careful not to cut into the old, woody parts of the plant, as it may not regrow from there. As we approach our first frost around mid- October, stop pruning to allow the plant to harden off for winter.

You can start harvesting thyme in late June, about 70 days after planting, and continue through late October. The best flavor comes just before the plant flowers. Look for healthy, vibrant sprigs.

To harvest, simply cut the stems, leaving at least a few inches of growth on the plant. Then, strip the leaves from the stems. Regular harvesting encourages the plant to produce more growth. As the first frost approaches in mid- October, harvest any remaining thyme to dry or freeze for later use.

Here in the Midwest, the two biggest problems with thyme are root rot from overwatering and fungal diseases due to humidity.

Root Rot

• What it looks like: Yellowing leaves, wilting, and a general decline in plant health. The roots will be brown and mushy instead of white and firm.
• What causes it: Overwatering, especially in poorly drained soil. Our wet-summer rainfall combined with heavy clay soils can create soggy conditions.
• How to fix/prevent it: Plant thyme in well-drained soil or raised beds. Water sparingly, only when the top inches feel dry. Improve drainage by amending the soil with compost.

Fungal Diseases

• What it looks like: Powdery mildew (white, powdery coating on leaves) or leaf spot (small, dark spots on leaves).
• What causes it: High humidity and poor air circulation. Our moderate-to-humid summers create ideal conditions for fungal growth.
• How to fix/prevent it: Provide good air circulation by spacing plants properly. Water at the base of the plant to avoid wetting the foliage. Remove and destroy any infected leaves.

Midwest Specific Challenges: The combination of moderate-to-hot heat, moderate-to-humid humidity, and wet-summer rainfall in the Midwest can create a perfect storm for thyme problems. Be vigilant about watering and provide good air circulation to keep your thyme healthy and productive.

Thyme makes a great companion plant for several vegetables and herbs in your Midwest garden. Rosemary, sage, and lavender share similar growing conditions (full sun and well-drained soil) and attract beneficial insects. Cabbage benefits from thyme's ability to repel cabbage moths. Strawberries thrive alongside thyme, as it helps deter pests and diseases. Tomatoes also benefit from thyme's pest-repelling properties and improved flavor. Avoid planting thyme near mint, as mint is very aggressive and can quickly overtake thyme.