By Jagdish Reddy | 10+ Years Gardening Experience
Reviewed Against: USDA Plant Hardiness Zone Map • Colorado State University Extension Yard & Garden Resources
Updated: June 2026

If you garden in Colorado, timing is everything. A Colorado planting calendar can help you decide exactly when to plant vegetables, fruits, herbs, and flowers based on your local growing conditions. From Denver and Colorado Springs to Grand Junction and mountain communities, planting dates can vary by several weeks because of elevation, frost dates, and climate differences.

This Colorado gardening calendar and planting guide is built around Colorado growing zones, average last spring frost dates, and first fall frost dates. Whether you are looking for a Colorado vegetable planting calendar, seed starting schedule, or a month-by-month Colorado planting schedule showing what to plant in Colorado throughout the year and when to plant vegetables, fruits, herbs, and flowers in your area, you will find practical planting recommendations here for every region of the state.

Not sure what to plant and when? Use the calculator below to generate a customized planting schedule based on your location and growing season.

Quick Answer: Colorado Planting Calendar Summary Cool-season vegetables (lettuce, peas, spinach, kale) go in the ground in March and April, 3 to 6 weeks before your last frost. Warm-season crops (tomatoes, peppers, beans, squash) wait until after last frost — May on the Front Range, June in the mountains. Fruit trees plant in March to April. Garlic goes in September to October for a July harvest. Use the tables below to find exact dates for your city and growing zone.

Printable Colorado Planting Calendar Want a printable version of this Colorado planting calendar? Scroll to the complete planting charts throughout this page. Screenshot or print any table directly from your browser, or copy the dates into your own garden planner. All charts are organized by crop, region, and growing zone for easy reference.

Colorado Planting Calendar At a Glance

Use this Colorado planting chart to find the best planting dates for vegetables, fruits, herbs, and flowers. Dates are organized by crop type and apply to most of the Front Range. Adjust by 2 to 4 weeks later for mountain areas and 2 weeks earlier for the Western Slope.

Crop Type	Best Planting Window	Notes
Cool-season vegetables	March – April	Tolerate light frost
Warm-season vegetables	May – June	After last frost only
Fruit trees (bare-root)	March – April	Before bud break
Strawberries / Berries	April – May	Zone-dependent
Annual herbs	May – June	Basil: after May 15
Perennial herbs	April – May	Cold-hardy types first
Hardy annual flowers	April	Pansies, snapdragons OK
Tender annual flowers	May 15 – June	After frost clears
Perennial flowers	April – May or Aug – Sep	Fall planting builds roots
Garlic	September – October	Overwinters, harvests July

What Can I Plant Right Now in Colorado?

Every spring, Colorado gardeners ask the same thing: what can I plant right now? The answer depends entirely on your month and elevation. Here is a fast reference for the whole year.

Find your month below. Front Range dates apply to Denver, Fort Collins, Boulder, Colorado Springs, and Pueblo. Mountain areas run 3 to 4 weeks later for most crops.

Month	Plant Outdoors Now	Start Indoors Now
January	Nothing outdoors	Onions, celery, leeks
February	Nothing outdoors	Onions, peppers (late Feb)
March	Spinach, peas, lettuce, radishes (Front Range)	Tomatoes, peppers, eggplant
April	Broccoli, kale, chard, carrots, beets, onion sets	Basil, squash, cucumbers
May	Tomatoes, peppers after last frost, beans, squash	Nothing needed
June	Late tomatoes, beans, corn, cucumbers, squash	Fall broccoli, cabbage
July	Beans (second round), radishes, lettuce (succession)	Fall broccoli transplants
August	Fall spinach, arugula, kale (early Aug)	Nothing typically
September	Garlic (plant for next year), spinach, radishes	Nothing typically
October	Garlic (last chance)	Nothing
November	Cover crops only	Nothing
December	Nothing	Plan and order seeds

Planning a new garden this year? Use the garden planner below to organize crops, planting dates, and garden space before you start planting.

Colorado Growing Zones and Frost Dates

Quick Answer: What Growing Zone Is Colorado? Colorado spans USDA Hardiness Zones 3 through 7. Denver and most of the Front Range fall in Zone 5b to 6a. Grand Junction and the Western Slope sit in Zone 6b to 7a. Colorado Springs is Zone 5b. Mountain towns like Breckenridge and Steamboat Springs fall in Zones 3 to 4. Check the USDA Plant Hardiness Zone Map at planthardiness.ars.usda.gov to find your exact zone.

Many Colorado gardeners lose tomatoes to a surprise frost even after a warm May — especially at higher elevations where cold air pools at night. Use this colorado garden calendar and planting dates by zone below to find your city, then adjust for local elevation.

City / Region	Zone	Last Spring Frost	First Fall Frost
Grand Junction	6b-7a	Apr 14	Oct 28
Pueblo	6a	Apr 22	Oct 10
Denver	5b-6a	May 7	Oct 7
Boulder	5b-6a	Apr 27	Oct 9
Fort Collins	5b-6a	May 5	Oct 3
Colorado Springs	5b	May 7	Oct 3
Durango	4b-5a	May 22	Sep 29
Steamboat Springs	4a-4b	Jun 3	Sep 6
Breckenridge	3b-4a	Jun 15	Aug 25
Leadville	3a-3b	Jun 20	Aug 15

Quick Answer: Colorado Last Frost Dates Denver’s average last spring frost is May 7. Colorado Springs: May 7 to May 15. Fort Collins and Boulder: late April to early May. Grand Junction: April 14. Durango: May 22. Steamboat Springs: June 3. Mountain towns above 9,000 feet like Leadville may see frost through late June. Always use local data — statewide averages can miss your actual conditions by 2 to 3 weeks.

Your last spring frost and first fall frost dates determine when many crops can be planted. Check your local frost dates using the calculator below.

Why Elevation Changes Everything

Every 1,000 feet of elevation gain adds roughly 3 to 5 days of frost risk at each end of the season. A garden at 8,000 feet near Steamboat Springs can have a growing window 6 to 8 weeks shorter than one in Denver.

Never rely solely on city-level frost charts. Valleys and north-facing slopes run colder than nearby benchmarks. A soil thermometer costs about $10 and tells you more than any published table.

Elevation	Last Spring Frost	First Fall Frost	Season Length
Below 5,000 ft	Apr 10 – Apr 20	Late October	185+ days
5,000 – 6,500 ft	Apr 20 – May 10	Early-Mid October	150-180 days
6,500 – 8,000 ft	May 10 – May 25	Late September	120-150 days
8,000 – 9,500 ft	May 25 – Jun 10	Early September	90-120 days
Above 9,500 ft	Jun 10 – Jul 1	Late August	60-90 days

Colorado Zone 5 vs Zone 6: Key Planting Differences

Factor	Zone 5 (e.g. Colorado Springs)	Zone 6 (e.g. Denver, Pueblo)
Last Spring Frost	Early-Mid May	Late April – Early May
Tomato Transplant Date	May 15 – May 25	May 7 – May 15
Pepper Transplant Date	May 20 – Jun 1	May 15 – May 25
Fall First Frost	Early October	Mid October
Growing Season	~145 days	~155-165 days
Melon Viability	Marginal (short-season only)	Reliable with good variety

Colorado Soil Temperature Planting Guide

Calendar dates are a starting point. Soil temperature is what actually triggers germination. Cold soil means slow germination, rot risk for beans, and stunted peppers. A cheap probe thermometer takes the guesswork out.

Key Insight Beans planted in 55°F soil germinate slowly and often rot. Wait until soil hits 60°F before planting. Peppers placed in cool soil stall for weeks. Soil temp matters more than air temp for warm-season crops.

Crop	Min Soil Temp	Ideal Soil Temp
Peas	40°F	55-65°F
Spinach / Lettuce	40-45°F	60-65°F
Radishes / Carrots	45-50°F	60-70°F
Beets / Chard	50°F	65-75°F
Onions	50°F	65-75°F
Tomatoes	60°F	65-85°F
Beans (all types)	60°F	70-80°F
Corn	60°F	65-85°F
Peppers / Eggplant	65°F	75-85°F
Cucumbers	65-70°F	75-85°F
Squash / Melons	65-70°F	75-85°F

Colorado Seed Starting Calendar: When to Start Seeds Indoors

Count back from your local last frost date. Denver’s last frost is roughly May 7. Adjust for your city using the frost date table above.

Crop	Weeks Before Frost	Denver Start Date
Onions / Leeks	10-12 weeks	Feb 13 – Feb 27
Celery	10-12 weeks	Feb 13 – Feb 27
Peppers / Eggplant	8-10 weeks	Feb 27 – Mar 13
Tomatoes	6-8 weeks	Mar 13 – Mar 27
Broccoli / Cauliflower	6-8 weeks	Mar 13 – Mar 27
Cabbage	6-8 weeks	Mar 13 – Mar 27
Kale / Chard	4-6 weeks	Apr 1 – Apr 14
Basil	4-6 weeks	Apr 1 – Apr 14
Squash / Cucumbers	3-4 weeks	Apr 14 – Apr 21
Melons	3-4 weeks	Apr 14 – Apr 21

Mountain gardeners: shift all dates 2 to 4 weeks later based on your local last frost. Steamboat Springs gardeners, for example, should start tomatoes in early to mid-April for a June transplant date.

What to Direct Sow Outdoors in Colorado

Crop	Sow Date (Front Range)	Notes
Peas	Mar 25 – Apr 10	Soil 40°F+, frost tolerant
Spinach	Mar 20 – Apr 10	Can handle light freeze
Lettuce	Apr 1 – Apr 15	Shade in summer heat
Radishes	Mar 25 – Apr 10	25-30 days to harvest
Carrots	Apr 1 – Apr 25	Soil 50°F+, thin well
Beets	Apr 5 – Apr 25	Direct sow only
Beans (bush)	May 15 – Jun 5	Soil 60°F+
Corn	May 20 – Jun 5	Plant in blocks, not rows
Sunflowers	May 10 – May 25	Direct sow after frost
Garlic	Sep 15 – Oct 15	Fall plant, July harvest

When to Plant Vegetables in Colorado for the Best Harvest

Best Cool-Season Vegetables to Plant Before Colorado’s Last Frost

Cool-season crops are Colorado’s most reliable producers. They handle light frost, grow fast, and often taste better in cool weather. Broccoli florets are sweeter after a frost. Lettuce turns bitter in heat.

Plant 3 to 6 weeks before your last frost date. In Denver, that means mid-March through mid-April for most cool-season crops.

Quick Answer: When to Plant Cool-Season Vegetables in Colorado Plant spinach, peas, lettuce, and radishes 4 to 6 weeks before your last frost date. In Denver, that is late March to mid-April. In Colorado Springs, aim for early to mid-April. Mountain gardeners should wait until mid-May.

When to Plant Tomatoes, Peppers, and Other Warm-Season Vegetables in Colorado

Warm-season crops need both air and soil temperatures to stabilize before going outside. Many Colorado gardeners lose tomatoes to a surprise frost after a warm stretch in early May.

In Denver, Memorial Day weekend is the traditional safe date. Most years you can push to May 15 to 20 if you watch the forecast. Colorado Springs gardeners should wait until after May 20.

Quick Answer: When to Plant Tomatoes in Colorado Plant tomatoes outdoors 1 to 2 weeks after your last frost date when soil is above 60°F. In Denver, this is May 15 to June 1. In Colorado Springs, May 20 to June 1. Mountain areas: late May to mid-June depending on elevation.

Vegetable	Front Range / Denver	Grand Junction	Mountain Areas (7,000+ ft)
Tomatoes (transplant)	May 15 – Jun 1	May 1 – May 15	Jun 1 – Jun 15
Peppers (transplant)	May 20 – Jun 5	May 5 – May 20	Jun 5 – Jun 20
Cucumbers	May 20 – Jun 1	May 1 – May 15	Jun 5 – Jun 15
Zucchini / Squash	May 15 – Jun 1	May 1 – May 15	Jun 1 – Jun 15
Green Beans	May 20 – Jun 5	May 5 – May 15	Jun 5 – Jun 20
Sweet Corn	May 20 – Jun 5	May 5 – May 15	Jun 10 – Jun 25
Eggplant	May 25 – Jun 5	May 10 – May 20	Jun 10 – Jun 20
Potatoes	Apr 20 – May 10	Apr 10 – May 1	May 20 – Jun 5
Onion sets	Apr 15 – May 1	Apr 5 – Apr 20	May 10 – May 25
Garlic (fall)	Sep 15 – Oct 15	Sep 20 – Oct 20	Sep 1 – Sep 30
Lettuce	Apr 1 – Apr 20	Mar 20 – Apr 10	May 1 – May 20
Spinach	Mar 25 – Apr 15	Mar 10 – Apr 1	Apr 25 – May 15
Broccoli (transplant)	Apr 15 – May 1	Apr 5 – Apr 20	May 15 – Jun 1
Carrots	Apr 1 – Apr 25	Mar 20 – Apr 10	May 1 – May 20
Kale	Apr 1 – Apr 20	Mar 20 – Apr 5	May 1 – May 15
Peas	Apr 1 – Apr 20	Mar 15 – Apr 1	May 1 – May 20

After choosing your crops, use our Plant Spacing Calculator to determine how much room each vegetable needs for healthy growth and better yields.

When to Plant Fruit Trees, Berries, and Fruits in Colorado

Best Time to Plant Apple, Pear, Peach, and Cherry Trees

Plant bare-root fruit trees as soon as the ground is workable, before buds break. In Denver, that is typically mid-March to mid-April. Container trees can go in from spring through early September.

Colorado’s late spring frosts can kill fruit blossoms even in Zone 6. Palisade on the Western Slope is famous for peaches precisely because its topography and warm climate protect blossoms. Elsewhere, choose late-blooming varieties and avoid north-facing planting spots.

Fruit Tree	Front Range Plant Date	Grand Junction	Zone Minimum
Apple	Mar 15 – Apr 15	Mar 1 – Apr 1	Zone 4
Pear	Mar 15 – Apr 15	Mar 1 – Apr 1	Zone 4
Peach	Apr 1 – May 1	Mar 15 – Apr 15	Zone 6 preferred
Tart Cherry	Mar 15 – Apr 15	Mar 1 – Apr 1	Zone 4
Sweet Cherry	Apr 1 – Apr 20	Mar 15 – Apr 10	Zone 5-6
Plum	Mar 15 – Apr 15	Mar 1 – Apr 1	Zone 4
Apricot	Apr 1 – Apr 20	Mar 15 – Apr 10	Zone 5 (frost risk)

Strawberries, Raspberries, and Blueberries in Colorado

Raspberries are one of the most reliable small fruits for Colorado. They handle cold winters, tolerate alkaline soil better than most berries, and produce heavily with minimal care.

Blueberries are the hard case. Colorado’s alkaline soil (often pH 7.5 to 8.2) is the opposite of what blueberries need (pH 4.5 to 5.5). Grow them in containers with acidified potting mix or do not bother.

Berry	Planting Window	Zone	Soil Note
Strawberries	Apr 20 – May 15	Zones 3-7	Well-drained, pH 6-7
Raspberries	Apr 1 – May 1	Zones 3-6	Alkaline-tolerant
Blackberries	Apr 15 – May 15	Zones 5-7	Needs shelter in Zone 5
Blueberries	May 1 – May 20	Zone 4+	Container + acid mix
Grapes	May 1 – May 20	Zones 5-7	Palisade area ideal
Currants	Apr 1 – May 1	Zones 3-6	Cold-hardy, reliable

When to Plant Herbs in Colorado Gardens

Annual Herbs: Basil, Cilantro, Dill, and Parsley

Basil is non-negotiable about warm weather. One late frost at 28°F turns it black overnight. Do not plant basil outside until nighttime temps stay reliably above 50°F — usually late May in Denver, and into early June in Colorado Springs.

Cilantro and dill do the opposite. They bolt fast in Colorado’s summer heat. Plant them in April and again in late August for a fall crop. Succession plant every 3 weeks for continuous harvest.

Perennial Herbs That Survive Colorado Winters

Mint, chives, thyme, oregano, and sage overwinter reliably in Zones 5 and warmer. Rosemary is marginal in Zone 5 — a south-facing wall with good drainage keeps it alive most winters.

Lavender thrives in Colorado. The state’s alkaline, well-drained soil suits it perfectly. It survives in Zone 5 with proper drainage. Plant it in full sun and it will likely outlast most other perennials in your garden.

Herb	Plant Date (Denver)	Perennial?	Key Note
Basil	May 20 – Jun 1	No	Frost-kills instantly
Cilantro	Apr 10 – Apr 25	No	Succession plant
Dill	Apr 10 – Apr 25	No	Direct sow only
Parsley	Apr 15 – May 1	Biennial	Slow germinator
Chives	Apr 1 – Apr 15	Yes (Z3+)	Very cold-hardy
Mint	May 1 – May 15	Yes (Z3+)	Use containers
Thyme	Apr 20 – May 5	Yes (Z4+)	Drought-tolerant
Oregano	Apr 20 – May 5	Yes (Z4+)	Dry soil OK
Sage	Apr 20 – May 5	Yes (Z4+)	Xeriscape-friendly
Rosemary	May 10 – May 25	Yes (Z6+)	Marginal in Z5
Lavender	May 1 – May 20	Yes (Z5+)	Thrives in CO soil

When to Plant Annual and Perennial Flowers in Colorado

Best Annual Flowers to Plant After Frost Danger Has Passed

Tender annuals like marigolds, zinnias, petunias, and impatiens all need to wait until after last frost. In Denver, plant after May 7. In Colorado Springs, after May 15. Plant too early and one frost undoes everything.

Hardy annuals are different. Pansies, snapdragons, and sweet alyssum handle light freezes. You can plant these 3 to 4 weeks before last frost. They are some of the first color you can get in a Colorado spring garden.

Colorado Perennial Flowers That Survive Harsh Winters

Colorado-native perennials are your most reliable long-term investment. Coneflower (Echinacea), penstemon, yarrow, black-eyed Susan, and blue grama grass are all adapted to the state’s soil, altitude, and climate swings.

Plant perennials in spring (April to June) or early fall (August to September). Fall planting gives roots time to establish before winter, often producing a stronger plant the following year.

Flower	Plant Date (Denver)	Type	Zone
Pansies	Apr 1 – Apr 20	Hardy Annual	All zones
Snapdragons	Apr 10 – Apr 25	Hardy Annual	All zones
Sweet Alyssum	Apr 10 – Apr 25	Hardy Annual	All zones
Marigolds	May 15 – May 30	Tender Annual	All zones
Zinnias	May 15 – Jun 1	Tender Annual	All zones
Petunias	May 10 – May 25	Tender Annual	All zones
Sunflowers	May 10 – May 25	Tender Annual	All zones
Impatiens	May 20 – Jun 1	Tender Annual	Zones 4-7
Coneflower	Apr 15 – May 15	Native Perennial	Zones 3-7
Black-eyed Susan	Apr 15 – May 15	Native Perennial	Zones 3-7
Penstemon	Apr 15 – May 15	Native Perennial	Zones 3-7
Yarrow	Apr 20 – May 10	Native Perennial	Zones 3-7
Lavender	May 1 – May 20	Perennial	Zones 5-7
Salvia (perennial)	Apr 20 – May 15	Perennial	Zones 4-7
Blue Grama Grass	May 1 – May 20	Native Perennial	Zones 3-7

Colorado Planting Calendar by USDA Growing Zone

What to Plant in Colorado Zone 3 and 4 (High Mountain Areas)

Zone 3 covers the highest elevations in Colorado: Leadville, parts of Summit County, and isolated San Juan Mountain communities. Zone 4 includes towns like Breckenridge, Steamboat Springs, and Glenwood Springs.

Growing seasons here run 60 to 120 days. Focus on fast-maturing, cold-hardy crops. Short-season tomatoes (under 65 days) are possible in Zone 4 with a sheltered, south-facing bed. Zone 3 should not count on tomatoes reliably ripening outdoors.

• Fast crops: radishes (25 days), lettuce (45 days), spinach (40 days), kale (50 days)
• Root vegetables: carrots, beets, turnips all handle cold well
• Best tomato varieties for Zone 4: Stupice, Siletz, Legend, Sub-Arctic Plenty
• Use row covers, cold frames, and dark-colored raised beds to gain extra weeks

What to Plant in Colorado Zone 5 Throughout the Growing Season

Zone 5 covers Colorado Springs, Gunnison, Woodland Park, and many mid-elevation Front Range communities. Last frost typically runs May 1 to May 15.

You can grow the full range of cool-season crops plus reliable warm-season crops if you use short-to-mid-season varieties. Tomatoes with 70 to 80 day maturity work well. Avoid 90+ day types.

What Grows Best in Colorado Zone 6 Gardens

Denver, Fort Collins, Boulder, and Pueblo fall in Zone 6. This is where most Colorado gardeners can reliably grow tomatoes, peppers, sweet corn, and many fruit crops. Longer growing seasons and milder winters make Zone 6 the most productive zone in the state for warm-season gardening.

Tomatoes, peppers, cucumbers, melons (short-season types), sweet corn, and most herbs grow reliably. Peach trees can survive Zone 6 winters but blossom damage from late frosts is a recurring risk.

Colorado Zone 7 Planting Dates for Vegetables, Fruits, and Flowers

Zone 7 is primarily the Grand Junction area, the Palisade bench, and lower elevations of the Western Slope. This is Colorado’s warmest gardening zone with the longest season.

Grand Junction gardeners can plant cool-season crops in March and warm-season crops in late April to early May. Peaches, wine grapes, and apricots are commercially viable here. The region’s low humidity also means fewer fungal disease problems than wetter climates.

Colorado Planting Calendars for Denver, Colorado Springs, Grand Junction and Other Regions

Denver Planting Calendar

Denver sits at 5,280 feet in Zone 5b to 6a. Over 300 sunny days per year helps. The main threats are late spring frosts in May, hailstorms in June and July, and early fall frosts in October.

Hail cloth over tomatoes and peppers is a smart investment. A $20 piece of hail netting can save an entire season’s work.

Colorado Springs Planting Calendar

Colorado Springs runs about a week behind Denver for most planting dates. Zone 5b with a last frost typically between May 7 and May 15. The city sits at 6,000+ feet, and its varied terrain creates real frost pockets — particularly in lower-lying neighborhoods and areas near Monument Creek.

Hail risk is significant. The Pikes Peak region sees frequent afternoon storm activity from June through August. Use hail cloth over tomatoes and peppers once they are established.

Stick to shorter-season varieties here: tomatoes under 75 days, peppers under 80 days. Crops like kale, broccoli, carrots, and spinach do very well. The cooler nights actually improve flavor in leafy greens and root vegetables compared to warmer Front Range cities.

Grand Junction and Western Slope Planting Calendar

Grand Junction is Colorado’s warmest gardening hub. Zone 6b to 7a with last frost around April 14. Gardeners here have a genuine head start on most of the state.

The Arkansas Valley and San Luis Valley also have unique microclimates. The San Luis Valley’s high elevation (7,500+ feet) creates very cold overnight temps despite its southern latitude.

Fort Collins and Boulder Planting Calendar

Very similar to Denver in timing. Fort Collins last frost averages May 5. Boulder benefits from slightly warmer conditions due to its position against the Flatirons. Both cities fall in Zone 5b to 6a.

Raised Bed Planting Calendar for Colorado Gardens

Raised beds change the planting game in Colorado. Soil in a 12-inch raised bed warms 2 to 4 weeks faster than in-ground soil in spring. That is a meaningful head start in a short-season state.

If you’re building new beds this season, try our Raised Bed Soil Calculator to estimate how much soil you’ll need before planting.

Dark-colored or metal raised beds gain even more heat. Black plastic mulch over raised bed soil can raise temp 5 to 10°F and extend your effective growing window by 3 to 4 weeks at both ends of the season.

Benefit	In-Ground Garden	Raised Bed (Colorado)
Spring soil warm-up	Standard timing	2-4 weeks earlier
Frost drain	Cold air pools at soil level	Better drainage reduces frost risk
Soil control	Limited	Full control of mix
Watering efficiency	Some runoff	Better retention + less waste
Fall extension	Standard	Row covers extend 3-4 more weeks

Colorado Fall Planting Calendar

Fall gardening is underused in Colorado. Many gardeners stop after summer crops wind down, but September and October offer ideal cool conditions for a second round of fast crops.

Count back from your first fall frost date. Plant crops that mature in time before the killing freeze.

Crop	Days to Harvest	Plant By (Denver)	Plant By (Mtn Areas)
Radishes	25-30 days	Sep 10	Aug 20
Spinach	40-50 days	Aug 25	Aug 5
Lettuce	45-55 days	Aug 20	Aug 1
Arugula	35-40 days	Sep 1	Aug 15
Kale	50-65 days	Aug 15	Jul 25
Asian Greens	30-45 days	Sep 1	Aug 15
Beets (baby)	45-55 days	Aug 20	Aug 1
Garlic	Overwinters	Sep 15 – Oct 15	Sep 1 – Sep 30

Colorado Native Plants Planting Calendar

Native plants are the most low-maintenance option for Colorado gardens. They are adapted to the altitude, alkaline soil, dry conditions, and temperature swings that challenge non-native plants.

Colorado State University Extension and Denver Botanic Gardens both recommend integrating natives into residential landscapes to reduce water use and maintenance.

Native Plant	Plant Date	Type	Water Needs
Blue Grama Grass	May 1 – Jun 1	Grass	Very low
Penstemon	Apr 15 – May 15	Perennial flower	Low
Yarrow	Apr 20 – May 15	Perennial flower	Very low
Coneflower (Echinacea)	Apr 15 – May 20	Perennial flower	Low-medium
Rocky Mtn Columbine	Apr 15 – May 15	Perennial flower	Low-medium
Rabbitbrush	May 1 – Jun 1	Shrub	Very low
Apache Plume	Apr 20 – May 20	Shrub	Very low
Wild Bergamot	May 1 – Jun 1	Perennial herb	Low
Prairie Dropseed	May 1 – Jun 1	Grass	Very low

Want to attract more bees, butterflies, and beneficial insects? Use our Pollinator Plant Finder to discover pollinator-friendly plants that grow well in Colorado.

Colorado Gardening for Beginners: What to Plant and When

If this is your first Colorado garden, start simple. The state’s climate will test you with late frosts, summer hail, dry air, and early fall freezes.

Easiest Crops to Grow in Colorado

• Zucchini and summer squash: almost impossible to fail in Colorado
• Kale: spring through fall, handles frost, thrives in Colorado sun
• Radishes: 25-day turnaround, great for first-time growers
• Bush beans: plant once in May, harvest all summer
• Cherry tomatoes: ripen faster and more forgiving than slicing types
• Chives, mint, thyme: nearly indestructible perennials
• Sunflowers: direct sow after frost, zero maintenance
• Garlic: plant in fall, harvest next summer, minimal effort

What First-Time Colorado Gardeners Should Avoid

• Heirloom tomatoes over 90 days: season is too short outside Zone 6
• Watermelons: need more heat than most of Colorado reliably provides
• Blueberries in-ground: soil pH is too alkaline without major amendment
• Basil before late May: one cold night kills it
• Daily light watering: check 2 inches deep before watering in Colorado’s dry climate

Tips for Extending the Growing Season in Colorado

• Row covers (frost cloth): protect from late spring frost and extend fall harvest by 3 to 4 weeks
• Cold frames: get cool-season crops going 4 to 6 weeks earlier than open-ground planting
• Black plastic mulch: raises soil temp 5 to 10°F, meaningful for warm-season crops in short-season areas
• Raised beds: warm up faster and drain better, reducing frost damage risk
• Succession planting: stagger radishes, lettuce, and spinach every 2 to 3 weeks
• Fall garlic: plant September to October, overwinters, harvests in July
• South-facing walls: position heat-loving crops against a south-facing structure to capture reflected warmth

Common Colorado Planting Mistakes That Hurt Your Harvest

Planting Warm-Season Crops Too Early

A warm week in early May tricks Colorado gardeners every year. Then a cold snap hits May 20 and wipes out freshly planted tomatoes and peppers. Check the 10-day forecast and wait until nighttime temps stay above 45°F before transplanting.

Choosing Long-Season Varieties

A tomato listed at 90 days will not ripen before fall frost in most Colorado locations. Choose varieties under 75 days for the Front Range and under 65 days for mountain gardens. Same rule applies to winter squash and melons.

Ignoring Elevation and Local Microclimates

A neighbor in a lower part of town or on a south-facing slope may have frost dates a week or two different from yours. A valley location can be 5°F colder overnight than a nearby bench or hillside.

Overwatering in Colorado’s Dry Climate

Colorado’s low humidity makes the soil surface look dry when there is moisture 2 inches down. Most established plants in Colorado do better with deep, infrequent watering than daily light watering. Check 2 inches down before watering.

Colorado Xeriscape Planting Calendar

Colorado averages 14 to 17 inches of rain per year on the Front Range and as little as 8 inches in Grand Junction. Plant xeriscape plants in spring (April to June) or early fall (August to September). Fall planting gives roots time to establish before summer heat arrives.

Xeriscape Plant	Best Plant Time	Water Needs
Blue Grama Grass	May – Jun	Very low (native)
Rabbitbrush	Apr – Jun	Very low (native)
Apache Plume	Apr – Jun	Very low (native)
Lavender	May – Jun	Low once established
Russian Sage	May – Jun	Low once established
Yarrow	Apr – May	Very low (native)
Penstemon	Apr – May	Low (native)
Agastache	May – Jun	Low once established
Catmint	Apr – May	Low once established
Buffalo Grass (seed)	May – Jun	Very low (native)

Water regularly through the first season. After that, most Colorado natives need little to no supplemental irrigation. Do not overwater — these plants come from dry climates and rot in wet soil.

Colorado Greenhouse and High Tunnel Planting Calendar

An unheated greenhouse or high tunnel adds 4 to 8 weeks to each end of the Colorado growing season. That is often the difference between a successful pepper harvest and a failed one in Zone 5 or higher elevation areas. A small heater keeping temps above 35°F extends that window even further.

The table below shows how much earlier greenhouse gardeners can start key crops compared to open-garden timing in Denver.

Crop	Greenhouse Start (Denver)	Open Garden Start
Cool greens (lettuce, spinach)	Feb 15 – Mar 1	Mar 25 – Apr 10
Peas	Feb 20 – Mar 5	Apr 1 – Apr 15
Tomatoes (transplant in)	Apr 15 – May 1	May 15 – Jun 1
Peppers (transplant in)	Apr 20 – May 5	May 20 – Jun 5
Cucumbers	Apr 20 – May 1	May 20 – Jun 1
Fall crops (spinach, kale)	Sep 15 – Oct 1	Aug 15 – Sep 1

High tunnels (unheated plastic covered hoops) give similar timing benefits. CSU Extension has tested high tunnels extensively across Colorado and reports season extensions of 4 to 10 weeks depending on location and tunnel design.

Colorado Hail Protection for Gardens

Hail is one of the most underappreciated threats in Colorado gardening. The Front Range sits in Hail Alley, one of the most hail-prone regions in North America. June and July are peak hail months. A 10-minute storm can shred a season’s worth of work.

• Hail cloth (shade netting rated for hail): install over raised beds and high-value crops in May, reusable year to year
• Wire cages with shade cloth: good protection for tomatoes and peppers, also blocks wind
• Watch weather apps in June and July: most hail storms are predictable 30 to 60 minutes out
• Recovery: hail-damaged plants often bounce back if the growing point is intact — cut shredded leaves, water lightly, wait a week
• Backup crops: fast-maturing radishes, lettuce, and beans can replace a hail-damaged planting within weeks

Hail cloth costs $15 to $40 for a raised bed-sized section and pays for itself the first time it saves a tomato planting. It is one of the most practical season investments a Colorado gardener can make.

Frequently Asked Questions About Planting in Colorado

When is it safe to plant tomatoes outside in Colorado?

Wait until after your local last frost date and nighttime temps consistently stay above 45°F. Denver: May 15 to June 1. Colorado Springs: May 20 to June 1. Mountain areas above 7,000 feet: late May to mid-June.

What vegetables grow best in Colorado?

Cool-season vegetables perform reliably across all of Colorado: kale, spinach, lettuce, peas, broccoli, carrots, and radishes. For warm-season crops, zucchini, green beans, and cherry tomatoes are the most dependable statewide. Warm zones can add peppers, cucumbers, and sweet corn.

When should I start seeds indoors in Colorado?

Tomatoes and peppers: 6 to 8 weeks before last frost (mid-March for Denver). Onions: 10 to 12 weeks before last frost (late January to early February). Mountain gardeners shift all dates 2 to 4 weeks later based on local last frost.

What month should I start a garden in Colorado?

Begin planting outdoors in March or April with cool-season crops. In the mountains, April or May. Warm-season planting starts after your last frost date, which is May for most of the Front Range and June for higher elevations.

What can I plant in Colorado right now?

It depends on the month and your location. In March and April, plant cool-season crops outdoors: spinach, peas, lettuce, kale, and radishes. In May, wait for your last frost date then add tomatoes, peppers, beans, and squash. In September, plant garlic and a fall round of spinach and radishes. Use the month-by-month table near the top of this page for a full breakdown by season.

What growing zone is Colorado?

Colorado spans Zones 3 through 7. Denver is Zone 5b to 6a. Grand Junction is Zone 6b to 7a. Colorado Springs is Zone 5b. The high mountains above 9,000 feet fall in Zones 3 to 4. Verify your zone at the USDA Plant Hardiness Zone Map: planthardiness.ars.usda.gov

Final Thoughts on the Colorado Planting Calendar

A gardener in Grand Junction can plant tomatoes nearly a month earlier than someone in Breckenridge. That is why location matters more than any statewide planting chart. Use your actual elevation and local frost dates, not what a Denver-based article says.

Use this colorado planting guide as your starting framework, then adjust based on what you observe in your own yard. Soil temperature, local frost history, and your specific elevation will always matter more than any generalized planting chart.

For region-specific data, Colorado State University Extension (extension.colostate.edu) publishes county-specific planting guides that go deeper than any national source. Your county extension office is the most accurate resource for local Colorado planting dates.

Reference Links:

1. USDA Plant Hardiness Zone Map

2. Colorado State University Extension – Yard & Garden

Disclaimer: Gardening information on Garden Truth is for educational purposes only. Results vary by climate, soil, weather, and growing conditions. For region-specific advice, consult your local USDA Cooperative Extension Service before making major gardening or soil changes.