Planting
To plant a garden in Colorado, timing is everything—your elevation zone dictates whether you start in early March or wait until May.
Colorado’s diverse elevation zones mean your garden’s planting schedule can vary dramatically—from early spring in lowlands to late summer in the mountains. Get the exact frost-free dates and best planting times to maximize your harvest.
Whether you’re growing General Garden Plants (Colorado) 🌱 or heat-loving tomatoes, knowing when to plant saves you from frost damage or wasted effort. The Front Range and Western Slope have different rules than the Eastern Plains, and mountain gardens often start later.
Below, I break down the ideal planting windows by zone, soil prep tips, and how to adjust for Colorado’s unpredictable weather—so you can enjoy a bountiful harvest all season long.
Colorado frost-free dates by elevation zone: key planting windows
Colorado’s elevation zones create dramatic differences in frost-free dates—from April 15 in Denver to June 1 in high mountain regions. Understanding these windows helps you time cool-season crops like spinach and warm-season crops like tomatoes perfectly. Each zone (2,500–10,000+ ft) has unique frost risks and growing seasons.
For example, Colorado Springs (6,000 ft) typically sees its last frost around April 30, while Grand Junction (4,500 ft) warms up by March 20. Mountain areas like Aspen (8,000 ft) may not be frost-free until June 15.
These variations mean your planting schedule must adapt sharply depending on where you garden.
| Elevation Zone (ft) | Last Frost Date | First Frost Date | Cool-Season Planting | Warm-Season Planting | Growing Season Length |
|---|---|---|---|---|---|
| 2,500–4,000 (Front Range Lowlands) | March 15–April 1 | October 15–November 1 | March–April | April 15–May 15 | 180–210 days |
| 4,000–6,000 (Denver/Colorado Springs) | April 1–April 15 | October 1–October 15 | April–May | May 1–May 30 | 150–180 days |
| 6,000–8,000 (Mountain Foothills) | April 15–May 1 | September 15–October 1 | May–June | June 1–July 1 | 120–150 days |
| 8,000–10,000+ (High Mountains) | May 15–June 15 | August 15–September 15 | June–July | July 1–August 1 | 90–120 days |
Use these frost-free dates to plan your cool-season crops like peas, lettuce, and broccoli, which thrive in cooler temperatures. Plant them 4–6 weeks before your last frost date for optimal growth.
For warm-season crops such as tomatoes, peppers, and cucumbers, wait until 2 weeks after your last frost to avoid cold damage.
In lower elevations (2,500–4,000 ft), you can start warm-season crops indoors in March and transplant outdoors by April 15. Meanwhile, high-elevation gardens (8,000+ ft) may need to wait until June or July for safe planting.
This delay allows you to focus on hardy cool-season crops like potatoes and kale during the shorter growing season.
Colorado’s microclimates add another layer of complexity. Urban areas like Denver often experience heat islands, extending the growing season by 1–2 weeks compared to rural areas. Conversely, mountain valleys can trap cold air, delaying frost-free dates by 3 weeks or more.
Always check local USDA hardiness zone maps and historical frost data for your specific location.
For fall planting, aim to sow cool-season crops 10–12 weeks before your first frost date. In Denver (Zone 5b), this means starting in early August, while Colorado Springs (Zone 6a) can extend planting until mid-September.
High-elevation areas may only allow for late July plantings due to earlier frosts.
If you’re unsure about your local frost dates, use a frost calendar from your county extension office or rely on historical averages.
Many Colorado gardeners also use row covers or cold frames to extend planting windows by 2–4 weeks, especially in higher elevations where the season is shorter.
Remember, soil temperature matters just as much as air temperature. Wait until the soil reaches at least 60°F for warm-season crops. You can test this with a soil thermometer or use your finger—if the soil feels warm to the touch, it’s ready for planting.
This rule applies across all elevation zones but becomes critical in cooler mountain regions.
By aligning your planting schedule with your elevation zone’s frost-free dates, you
Best plants to grow in each Colorado elevation zone
Colorado’s elevation zones create unique microclimates where potatoes thrive at 9,000 feet while okra flourishes in 4,000-foot valleys. The key is matching cold-hardy crops to high altitudes and heat-tolerant varieties to lower elevations. Even within cities like Denver, urban heat islands can shift planting windows by weeks.
For high-elevation gardens (6,500–10,000+ ft), focus on cool-season staples like kale, potatoes, and rhubarb. These plants handle shorter growing seasons and cooler soils. Meanwhile, lowland areas (3,500–6,000 ft) can support peppers, squash, and tomatoes with longer, warmer seasons.
🌱 Top Plants by Elevation Zone
- 3,500–5,000 ft (Front Range, Pueblo): Peppers, Okra, Sweet Potatoes, Corn, Basil
- 5,000–7,000 ft (Denver, Colorado Springs): Tomatoes, Zucchini, Bush Beans, Cucumbers, Herbs
- 7,000–9,000 ft (Mountain Foothills): Potatoes, Kale, Carrots, Peas, Radishes, Swiss Chard
- 9,000+ ft (High Mountains): Rhubarb, Brussels Sprouts, Turnips, Cabbage, Hardneck Garlic
Pro Tip: Use row covers in high elevations to extend the growing season by 2–4 weeks.
In urban areas, microclimates can create exceptions. For example, Colorado Springs’s Pikes Peak region (6,000–7,000 ft) often sees earlier last frosts than Denver, allowing tomatoes to ripen by late August. Meanwhile, heat-loving crops like eggplant struggle above 6,500 feet unless planted in sheltered microclimates.
For high-altitude gardens, prioritize fast-maturing varieties (e.g., bush beans in 55 days vs. pole beans’ 70 days). Cold-hardy greens like spinach and lettuce can even overwinter in protected beds at 8,000 feet.
In contrast, lowland gardens can experiment with tropical crops like sweet potatoes or longan peppers with proper irrigation.
Don’t forget perennials! Asparagus and rhubarb thrive in high elevations, while rosemary and lavender prefer drier, lower-altitude climates. Succession planting is key in shorter seasons—sow radishes every 2 weeks for continuous harvests.
Start by testing your local frost dates (check Almanac.com for your ZIP code) and adjust planting times accordingly. With the right crop selection, even Colorado’s extreme elevations can yield bountiful gardens! 🌿