Thyme in Zone 4B — Mountain West

Thyme is a fantastic herb to grow in our Mountain West gardens. Its earthy, slightly floral flavor elevates everything from roasted meats to hearty stews, and the satisfaction of snipping fresh sprigs from your own garden is hard to beat. Plus, the intense sunlight we get here really concentrates the oils, giving your Thyme an exceptional flavor.

Our high altitude, short growing season, and alkaline soil can present challenges, but Thyme is surprisingly adaptable. With a 128-day growing season, getting your timing right and providing well-drained soil will set you up for success.

Starting Thyme indoors is an option, particularly if you want a head start on our short growing season, but it's not always necessary. Thyme is slow to get going from seed, so it's best for gardeners who want a lot of Thyme or a specific variety.

If you choose to start indoors, sow seeds mid-March through early April, about eight weeks before you plan to transplant. Use seed trays and a good seed-starting mix, and provide consistent warmth and bright light – a grow light is helpful here. Bottom watering is ideal to prevent damping off; just set the tray in a shallow dish of water until the soil surface is moist. Remember, our late springs mean you'll need to be patient!

Transplanting Thyme outdoors is best done mid-May through mid-June, after the risk of frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the intense sun and cooler nights we often experience.

Space your Thyme plants 8-12 inches apart in a sunny spot with well-drained soil. Keep an eye on the weather forecast – a late-season frost can still happen, so be prepared to cover your transplants if needed. For many of us in the Mountain West, buying established Thyme plants from a local nursery is the easiest way to get a jump start on the season, and it saves you from waiting a full season for a tiny seedling to mature.

Direct sowing Thyme is possible, but it can be slow, and you might not get a harvest in the first year. If you choose this method, sow seeds mid-May through late June, when the soil has warmed up.

Prepare a well-draining seedbed, and lightly press the tiny seeds into the soil. Keep the soil consistently moist until germination, which can take a couple of weeks. Thin seedlings to 8-12 inches apart. Direct sowing works, but be prepared to be patient and diligent with watering, especially in our dry climate.

Thyme thrives in dry conditions, making it well-suited to our arid Mountain West climate. Overwatering is a much bigger threat than underwatering.

During the spring, water only when the top two inches of soil are dry to the touch – use the "finger test." Once established, Thyme needs very little supplemental water, usually about ½ inch per week, or less if we get any rainfall. Water at the base of the plant to avoid wetting the foliage, which can encourage fungal problems, even in our low humidity.

Signs of underwatering include wilting or yellowing leaves, while overwatering can lead to root rot, indicated by soft, brown stems near the soil line. A light mulch of gravel or small stones can help improve drainage and prevent soil from splashing onto the leaves. Remember, less is more when it comes to watering Thyme in our region.

Pruning Thyme is simple and helps keep the plant healthy and productive. The goal is to encourage new growth and prevent the plant from becoming too woody.

After flowering, which usually occurs in summer, cut back the stems by about one-third. Avoid cutting into the old, woody growth, as new shoots are unlikely to emerge from those areas. As the first frost approaches in mid-September, stop pruning to allow the plant to harden off for the winter.

You can start harvesting Thyme late July through late September, about 70 days after planting. The best flavor is just before the plant flowers.

To harvest, simply snip off sprigs as needed, being careful not to remove more than one-third of the plant at a time. You can strip the leaves from the stems for immediate use, or dry the sprigs for later. Regular harvesting encourages new growth and keeps the plant productive throughout the season.

As the first frost approaches in mid-September, harvest any remaining Thyme you want to preserve. Dry the sprigs by hanging them upside down in a cool, dark place, or freeze the leaves in ice cube trays for easy use throughout the winter.

Thyme is generally trouble-free, but here are a couple of common issues to watch out for in the Mountain West:

Root Rot:

• What it looks like: Yellowing leaves, wilting, and soft, brown stems near the soil line.
• What causes it: Overwatering and poorly drained soil. Our alkaline soil can sometimes retain too much moisture.
• How to fix/prevent it: Ensure your Thyme is planted in well-draining soil. Water sparingly, only when the top two inches of soil are dry. Improve drainage by adding gravel or sand to the planting area.

Fungal Diseases:

• What it looks like: Powdery mildew on leaves, or dark spots.
• What causes it: Although we have low humidity, fungal diseases can still occur, especially during periods of prolonged rain or if plants are overcrowded.
• How to fix/prevent it: Provide good air circulation by spacing plants adequately. Avoid overhead watering, and remove any affected leaves promptly.

Mountain West Specific Challenges: Our moderate-at-altitude heat, low humidity, and dry rainfall are generally favorable for Thyme. The biggest risk is overwatering, especially in spring when the soil is still cool. Be mindful of watering, and ensure your Thyme has excellent drainage to thrive in our unique climate.

Thyme makes a great companion plant for many garden vegetables and herbs. Rosemary, sage, and lavender all share similar growing requirements (full sun and well-drained soil) and can create a beautiful and fragrant herb garden. Cabbage and tomatoes benefit from Thyme's ability to repel certain pests, while strawberries enjoy the ground cover it provides.

Avoid planting Thyme near mint, as mint is very invasive and can quickly crowd out Thyme. Also, mint prefers moist conditions, which is the opposite of what Thyme needs to thrive.