Plants
Plant herbs in Colorado between mid-April and early September, timing your sowing to avoid late frosts and maximize the growing season 🌿.
Colorado’s diverse microclimates—from high-altitude mountain valleys to arid plains—mean your herb planting schedule must be precise to thrive. Get the exact months to sow, transplant, or harvest herbs in your zone, avoiding frost damage and maximizing flavor.
Whether you’re starting seeds indoors in March or direct-sowing hardy herbs like thyme in May, knowing your frost dates is the key. I’ll break down the best planting windows for Colorado’s USDA Zones 5-7, plus how to adjust for unpredictable weather.
You’ll also discover the top 5 herbs to grow here, when to harvest them for peak flavor, and pro tips for container gardening or extending your season with row covers.
Best months to plant herbs in Colorado’s 5 microclimate zones
Colorado’s diverse microclimates create unique challenges for herb gardeners. Whether you're in high-altitude Zone 4 or Southern Colorado's Zone 7, timing your plantings correctly ensures your herbs thrive. The key lies in understanding your last frost dates and selecting herbs that match your climate's extremes.
For Zone 4 gardeners in mountain valleys like Leadville or Aspen, the growing season is short—typically 90 days frost-free. In contrast, Zone 7 areas like Albuquerque or Colorado Springs foothills enjoy 180 frost-free days, allowing for longer plantings.
The Front Range (Zone 5) and Eastern Plains (Zone 6) fall somewhere in between, with 120-150 frost-free days.
Here’s how to align your herb planting with Colorado’s five key microclimates, including hardy perennials like thyme and tender annuals like basil. Use this guide to avoid frost damage and maximize your harvest.
In Zone 4, where frost lingers late, focus on cold-hardy perennials like thyme and chives. Start tender annuals like basil only after May 15, when soil temperatures exceed 55°F. Use row covers to extend your season for herbs like cilantro, which bolts quickly in heat.
For the Front Range (Zone 5), March is ideal for indoor seed starts of basil and dill. Transplant outdoors after April 30, once nighttime temperatures stay above 40°F. Rosemary and lavender thrive here but need well-draining soil to avoid root rot.
Gardeners in the Eastern Plains (Zone 6) enjoy an earlier start. Begin sowing cool-season herbs like cilantro and parsley in February for a spring harvest. Basil and dill can handle the hotter summers here, but mulch heavily to retain moisture in the dry prairie winds.
Southern Colorado’s Zone 7 offers the longest growing season. Plant warm-season herbs like basil as early as March, while cool-season herbs like cilantro can be sown in January for an early crop. Rosemary and oregano flourish here with minimal care, making them perfect for low-maintenance gardens.
No matter your zone, always harden off seedlings before transplanting and water deeply after planting. Monitor local frost forecasts—Colorado’s weather can shift quickly! For
How to adjust your herb planting schedule for Colorado’s unpredictable weather
Colorado’s unpredictable weather—from late spring frosts to sudden summer heatwaves—can derail even the most careful gardener’s plans. The key to success lies in flexible timing and smart protective strategies.
For example, my basil seedlings in Denver’s Zone 5 nearly froze in early May, but with the right adjustments, they thrived by June. Let’s explore how to adapt your herb schedule to Colorado’s whims.
Start by categorizing your herbs into cold-hardy and heat-sensitive varieties. Perennial herbs like thyme, oregano, and rosemary (Zone 5+) can handle Colorado’s late frosts down to 10°F, while tender annuals like basil and cilantro need soil temperatures above 50°F to germinate.
Knowing these distinctions lets you plan your schedule with confidence.
⚠️ callout warning ⚠️
⚠️ Late Frost Alert!
Colorado’s last frost dates vary wildly—April 15 in Denver but May 15 in Grand Junction. Check your local USDA Zone and use row covers for tender herbs until May 30 as a safety net. For Zone 4 areas, delay planting heat-lovers like basil until June 1 or start them indoors 8-10 weeks early.
For Zone 4 gardeners (high-altitude areas), begin indoor starts in March for basil, parsley, and dill. Use grow lights to simulate long daylight hours, and transplant outdoors only after May 15.
A simple trick I use is placing a black plastic mulch over soil beds in early spring—it warms the ground by 5-10°F, accelerating germination for cold-sensitive herbs.
Extend your growing season with seasonal adjustments. In Zone 5-6, sow cool-season herbs like cilantro and parsley in early September for fall harvests, while warm-season herbs like oregano and thyme can be planted as early as April 1.
For containers, move potted herbs to protected spots (like against south-facing walls) during unexpected cold snaps in September.
Don’t overlook microclimate advantages. Urban Denver gardens often experience heat islands that are 5-10°F warmer than rural areas. Use this to your advantage by planting heat-sensitive herbs like mint or lemon balm in these pockets.
Conversely, high-altitude gardens (e.g., Colorado Springs) may need row covers until June 10 to protect young plants.
Finally, monitor your herb maturity timeline. Most herbs reach harvestable size in 45-60 days, but Colorado’s short growing season demands efficiency.
For example, basil planted on June 1 in Zone 5 will likely bolt by September 15—plan to harvest leaves aggressively or succession-plant every 2 weeks for continuous yields. A harvest calendar with reminders for pruning and fertilizing keeps your herbs productive all season.