Thyme in Zone 5A — Mountain West

Thyme is a fantastic herb to grow in our Mountain gardens. The taste is incredible, especially when those cool nights even in summer concentrate the oils. It's so versatile in the kitchen, and there's real satisfaction in snipping fresh sprigs to add to your cooking. Plus, it thrives in our intense sun!

Our high altitude gardening definitely has its challenges, like that short season. But with Thyme, it's all about timing. Starting indoors or choosing the right transplant window gives it a great head start in our 138-day growing season.

Starting Thyme indoors is an option, especially if you want a jump start on the season. Begin in early to late March, about eight weeks before you plan to transplant outdoors. Use seed trays with a good seed-starting mix and provide consistent warmth and light.

Bottom watering is key when starting seeds indoors. It prevents damping-off and encourages strong root growth. Keep in mind that our spring weather can be unpredictable, so having those seedlings ready to go when the time is right can make all the difference.

Transplanting Thyme outdoors is best done in early May through early June, once the danger of hard frost has passed. Before you plant, 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.

Space your Thyme plants 8-12 inches apart to allow for their spreading growth habit. Honestly, because Thyme is slow from seed, buying starts from a local nursery is the way to go. It saves you a full season of waiting!

Direct sowing Thyme is possible, but be aware that it can be slow to germinate and establish. Sow seeds in early May through early July when the soil has warmed up. Prepare the soil well, ensuring it's loose and well-draining.

Thyme needs warmer soil temperatures to germinate, so keep the area consistently moist (but not soggy) until seedlings emerge. Thin seedlings to 8-12 inches apart once they're large enough to handle. Direct sowing can be a bit of a gamble with our short season, but it can work if you're patient.

Thyme is very drought-tolerant, which is a huge plus for our dry Mountain climate. Overwatering is a much bigger concern than underwatering with this herb. It thrives in well-drained, slightly dry soil, so resist the urge to water it too often.

During the active growing season (summer), water deeply but infrequently. A good rule of thumb is to check the soil about two inches deep. If it's dry to the touch, it's time to water. Give it about 1/2 inch of water per week, depending on rainfall.

Water at the base of the plant rather than overhead to prevent fungal issues. Our low humidity helps, but it's still a good practice. Signs of underwatering include wilting or drooping leaves, while overwatering can lead to yellowing leaves and root rot. A light layer of rock mulch around the base can help retain moisture and keep the soil cool.

Pruning Thyme is pretty minimal, but it helps keep the plant healthy and productive. After flowering, cut back the stems by about one-third to prevent the plant from becoming too woody. Avoid cutting into the old wood, as it may not regrow.

Prune lightly throughout the growing season to encourage bushier growth and more flavorful leaves. As the first frost approaches in late September, stop pruning to allow the plant to harden off for winter.

You can expect your first Thyme harvest starting in mid-July through early October, about 70 days after planting. The best flavor comes just before the plant flowers, so keep an eye out for those buds. You can harvest sprigs anytime you need them.

To harvest, simply cut the stems, then strip the leaves off. Be sure to leave enough foliage on the plant so it can continue to grow. Regular harvesting encourages continued production throughout the season.

As the first frost approaches in late September, harvest as much Thyme as you can and dry it for winter use. The cool nights even in summer help concentrate the flavors, so you'll have delicious Thyme all winter long.

Thyme is relatively easy to grow, but there are a couple of common problems to watch out for in our region: root rot from overwatering and fungal diseases.

Root Rot from Overwatering

• What it looks like: Yellowing leaves, wilting despite moist soil, and a general decline in plant health. The roots may appear brown and mushy.
• What causes it: Excess moisture in the soil, often due to overwatering or poor drainage. Our alkaline soil can also contribute if it doesn't drain well.
• How to fix/prevent it: Ensure well-draining soil, water only when the top two inches of soil are dry, and avoid overwatering. Improve drainage by adding sand or perlite to the soil.

Fungal Diseases

• What it looks like: Powdery mildew or other fungal growth on the leaves and stems.
• What causes it: Although our humidity is low, fungal diseases can still occur if plants are overcrowded or air circulation is poor.
• How to fix/prevent it: Provide adequate spacing between plants to promote air circulation. Water at the base of the plant to avoid wetting the foliage.

Mountain West Specific Challenges: Our moderate-at-altitude heat and low humidity are generally favorable for Thyme. However, our dry rainfall means you'll still need to water consistently, just be careful not to overdo it. The intense sun can also stress plants if they're not properly acclimated, so be sure to harden off transplants gradually.

Thyme makes a great companion plant for many other herbs and vegetables in your Mountain garden. Rosemary, sage, and lavender all thrive in similar conditions and benefit from Thyme's ability to attract beneficial insects. Thyme also helps repel cabbage moths, making it a good companion for cabbage.

Strawberries and tomatoes also benefit from being planted near Thyme. Thyme is thought to improve their flavor and vigor. Avoid planting Thyme near mint, as mint is very aggressive and can quickly overtake Thyme.