Grand County, CO — Planting Guide
Grand County is in USDA Zone 4a. The average last spring frost is May 28 and the first fall frost is September 19, giving you a growing season of approximately 114 days.
At an elevation of 5,397 ft, Grand County receives approximately 22.2 in of rainfall annually. Summer highs average 82°F with winter lows around 3°F. The predominant soil type is Loam.
Based on 31 years of NOAA climate station data, the last frost date here varies by 49 days year to year — ranging from April 29 in warm years to June 18 in cold years. The growing season is trending longer by about 2.73 days per decade. Grand County scores 33/100 (Challenging) on the Microclimate Index.
🌡️ Zone
4a (-30°F to -25°F min)
❄️ Last Frost
May 28
🍂 First Frost
September 19
📅 Growing Season
114 days
⛰️ Elevation
5,397 ft
🌧️ Annual Rainfall
22.2 in
Monthly Watering Calendar
When you'll need to water your garden — based on average monthly rainfall vs. the ~1 inch/week most gardens need.
View detailed monthly data
| Month | Avg Rainfall | Rainy Days | Extra Water Needed | Watering Effort |
|---|---|---|---|---|
| Jan | 1.7 in | 7 days | — | None |
| Feb | 1.2 in | 5 days | — | None |
| Mar | 1.9 in | 7 days | — | None |
| Apr | 2.1 in | 6 days | 2.2 in | High |
| May | 3 in | 6 days | 1.3 in | Moderate |
| Jun | 1.5 in | 4 days | 2.8 in | High |
| Jul | 2 in | 6 days | 2.3 in | High |
| Aug | 2.3 in | 7 days | 2 in | High |
| Sep | 1.6 in | 6 days | 2.7 in | High |
| Oct | 2.2 in | 5 days | 2.1 in | High |
| Nov | 1.5 in | 6 days | — | None |
| Dec | 1.2 in | 7 days | — | None |
Annual total: 22.2 in. Gardens typically need ~1 inch of water per week during the growing season. Months marked "None" for extra water are outside the active growing season for your zone — most gardens are dormant and don't need irrigation during those months.
Grand County Soil Profile
Soil Type
Loam
Soil pH
6.7-8.3
Drainage
Well Drained
Frost Risk Probability
Based on 31 years of NOAA weather station data from 3 stations
Beginners: Plant frost-sensitive crops (tomatoes, peppers, squash) after the "Safe" date on the left. Harvest or cover them before the "Protect by" date on the right. Hardy crops (lettuce, peas, kale) can go in the yellow transition zones.
How to read this table: "Conservative" means you're safe from frost 9 out of 10 years — best for beginners and frost-sensitive crops. "Average year" is the typical date. "Aggressive" means only 1 in 10 years is that warm — experienced gardeners with frost protection can try these dates.
| Planting Strategy | Last Spring Frost | First Fall Frost | Frost-Free Days |
|---|---|---|---|
| Conservative (safest) | Jun 18 | Oct 13 | 117 days |
| Cautious | Jun 8 | Sep 26 | 110 days |
| Average year | May 28 | Sep 19 | 114 days |
| Optimistic | May 13 | Sep 10 | 120 days |
| Aggressive (risky) | Apr 29 | Sep 3 | 127 days |
Not very — frost dates can vary by ±49 days year-to-year. Use the "Conservative" row in the table below, and keep row covers handy for surprise late frosts.
Yes — growing seasons are getting longer here (about 2.7 days per decade). Spring is arriving earlier than it used to. Good news for gardeners.
Gardening Difficulty Score
Grand County has challenging growing conditions. Season extension and careful variety selection are essential.
Local Gardening Help in Grand County
Free expert help is closer than you think. Your county's cooperative extension office connects you with trained gardeners, soil testing labs, and local programs — all specific to Grand County's climate and soil.
County Extension Office
Grand County Colorado State University Extension Extension Office
Phone: 970-491-6281
Visit Extension Office Website →
Extension offices are run by land-grant universities and funded by the USDA. Their advice is free, research-based, and tailored to your county's specific conditions.
Master Gardener Program
Free gardening help from trained volunteers
Master Gardeners are community volunteers who complete 40–60 hours of university horticultural training. They answer gardening questions, diagnose plant problems, and offer workshops — all free.
Many extension offices run a Master Gardener hotline where you can call or email with photos of plant problems for free diagnosis.
Soil Testing
Available through your extension office
Before amending your soil, get it tested. Your extension office offers soil testing (typically $10–$25) that tells you exact pH, nutrient levels, and amendment recommendations specific to what you want to grow.
Services Available in Grand County
Finding local nurseries & garden centers in Grand County
Why Buy Local
Local nurseries carry plants that are proven to grow in your area. Staff can give you advice specific to Grand County's soil and climate that big-box stores can't. Plants from local growers are typically hardier because they're already acclimated to your zone.
How to Find Them
Search for "nurseries near Grand County CO" or "garden center Grand County" on Google Maps. Also check with your extension office — they often maintain lists of reputable local nurseries and plant sales.
Community gardens & gardening groups
Community gardens are a great way to learn from experienced gardeners in your area, especially if you're limited on space. Search "community garden Grand County CO" or check your extension office and local parks department. Facebook groups like "Grand County Gardeners" or "Colorado Gardening" are also excellent for local advice and plant swaps.
What to Plant After Your Harvest
After your first crops finish, use the remaining frost-free days to grow a second round.
Sunlight & Day Length
Monthly daylight hours and peak sun — critical for onion varieties, photoperiod-sensitive plants, and solar garden planning.
Longest Day
14.8 hours
Summer solstice daylight
Shortest Day
9.2 hours
Winter solstice daylight
Peak Sun Hours
10.4 hr/day peak (summer)
Peak sun hours (green dashed line below) account for cloud cover — this is the usable direct sunlight your garden actually receives. Most vegetables need 6+ peak sun hours.
Onion tip: Your long summer days (14+ hours) support long-day onion varieties like Walla Walla, Sweet Spanish, and Ailsa Craig.
View detailed monthly data
| Month | Daylight Hours | Peak Sun Hours | Day Length |
|---|---|---|---|
| January | 9.4 hr | 5.3 hr | Short day |
| February | 10.5 hr | 6.3 hr | Short day |
| March | 11.7 hr | 6.8 hr | Short day |
| April | 13.1 hr | 7.3 hr | Neutral |
| May | 14.2 hr | 8.7 hr | Long day |
| June | 14.8 hr | 10.4 hr | Long day |
| July | 14.6 hr | 9.8 hr | Long day |
| August | 13.6 hr | 8.8 hr | Neutral |
| September | 12.2 hr | 8.9 hr | Neutral |
| October | 10.9 hr | 6.7 hr | Short day |
| November | 9.7 hr | 5.6 hr | Short day |
| December | 9.2 hr | 4.9 hr | Short day |
Peak sun hours factor in typical cloud cover — use these for solar panel and shade-planning calculations.
Soil Temperature & Composting Calendar
Monthly soil temps tell you when to plant warm-season crops, and when your compost pile is actively working.
Plant Warm Crops When
Soil reaches 60°F+
Soil rarely reaches 60°F — use black plastic mulch to warm soil.
Best Month to Compost
Jul
Microbial activity peaks when soil is warm.
Active Composting
2 months
Short season — insulate pile or use indoor vermicomposting.
View detailed monthly data
| Month | Soil 4" Deep | Soil 8" Deep | Compost Activity | Time to Finish |
|---|---|---|---|---|
| Jan | 1°F | 10°F | ❄️ Dormant | ~36 weeks |
| Feb | 1°F | 7°F | ❄️ Dormant | ~36 weeks |
| Mar | 11°F | 13°F | ❄️ Dormant | ~36 weeks |
| Apr | 25°F | 23°F | ❄️ Dormant | ~36 weeks |
| May | 42°F | 34°F | 🐢 Slow | ~24 weeks |
| Jun | 50°F | 44°F | 🐢 Slow | ~24 weeks |
| Jul | 58°F | 52°F | ♻️ Active | ~14 weeks |
| Aug | 59°F | 55°F | ♻️ Active | ~14 weeks |
| Sep | 49°F | 51°F | 🐢 Slow | ~24 weeks |
| Oct | 39°F | 39°F | ❄️ Dormant | ~36 weeks |
| Nov | 22°F | 30°F | ❄️ Dormant | ~36 weeks |
| Dec | 6°F | 17°F | ❄️ Dormant | ~36 weeks |
Highlighted rows = soil 60°F+ (safe for warm-season transplants). Compost finishes fastest during peak activity months.
Pest & Disease Pressure in Grand County
Computed from local climate patterns — warmer, humid conditions increase pest generations and fungal disease risk.
Insect Pest Pressure
Moderate — common pests appear but manageable with monitoring.
Disease Risk
Low disease risk — dry conditions reduce fungal problems.
Seasonal Risk
View 5 common pests in your area
| Pest | Risk Level | Peak Months |
|---|---|---|
| Aphids | Moderate | May, Jun, Jul, Aug |
| Cabbage worms | Low | Jun, Jul, Aug |
| Colorado potato beetle | Low | Jun, Jul |
| Flea beetles | Low | May, Jun, Jul |
| Slugs | Low | May, Jun, Jul, Aug, Sep |
Organic pest management tips
- Maintain healthy soil with regular compost additions to build natural pest resistance
- Practice crop rotation annually to break pest cycles
- Encourage beneficial insects with flowering herbs like dill, fennel, and yarrow
Cover Crops for Grand County
Cover crops protect bare soil, fix nitrogen, suppress weeds, and improve soil structure — with county-specific planting dates.
Fall Cover Crops (5 options) — Plant after harvest to protect soil over winter
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Daikon radish | Aug 5 | May 7 | — | Deep taproot breaks compaction, excellent for clay soils |
| Hairy vetch | Jul 12 | May 7 | ✓ Yes | Excellent nitrogen fixer, good for depleted soils |
| Oats | Aug 25 | May 7 | — | Quick biomass, winterkills in cold zones — no spring tillage needed |
| Winter rye | Jun 30 | May 14 | — | Suppresses weeds, prevents erosion, breaks up compacted soil |
| Winter wheat | Jun 27 | May 7 | — | Erosion control, weed suppression, good biomass |
Spring Cover Crops (2 options) — Build soil before the main growing season
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Buckwheat | Jun 1 | Jul 18 | — | Rapid growth, attracts pollinators, suppresses weeds |
| White clover | Apr 30 | Jul 25 | ✓ Yes | Living mulch, fixes nitrogen, permanent ground cover |
Summer Cover Crops (1 options) — Fill gaps and suppress weeds between plantings
| Crop | Plant By | Terminate | N-Fixing | Soil Benefit |
|---|---|---|---|---|
| Sunflowers | Jun 19 | Aug 29 | — | Deep roots break compaction, attract pollinators and beneficial insects |
Wind & Microclimate
Wind dries soil, stresses plants, and affects frost patterns. Understanding your exposure helps with garden placement.
Seasonal Wind Speed
Spring: 16 mph Summer: 12 mph
Fall: 11 mph Winter: 14 mph
Prevailing wind: W. Windy area — plant a windbreak hedge on the W side of your garden.
Windbreak Benefit
6.9/10
Moderately beneficial — a simple fence or trellis can protect delicate crops from wind stress.
Frost Pocket Risk
High
Hilly terrain with 1,266 ft of elevation range — cold air pools in low spots. Avoid planting frost-sensitive crops in valleys.
Rainwater Harvesting Potential
How much water you can collect, when to collect it, and what size system you need for your garden.
Annual Collection
11,064 gal
Per 1,000 sq ft of roof area (at 80% collection efficiency)
Recommended Setup
7 rain barrels (55 gal each)
For a typical 500 sq ft garden. Serious collectors: consider a 1,750 gal tank.
Legal Status
Limited
Your state has quantity limits on rainwater collection — check local regulations before installing large systems.
Best Collection Months
Apr, May, Aug, Oct
Highest rainfall months — your barrels will fill up quickly during these months.
Months to Draw From Storage
Feb, Nov, Dec
Dry months when you'll rely on stored water — size your storage for this gap.
Rainwater collection tips for your area
- Your county receives approximately 22.2 inches of rain per year
- A 1,000 sq ft roof can collect roughly 11,064 gallons annually
- Check CO state regulations — rainwater harvesting has quantity limits
- Stock up on stored water before your dry season (Feb, Nov, Dec)
- Use a first-flush diverter to keep roof debris out of your collection
Soil & Growing Conditions in Grand County
Soil Type
Loam
Soil pH 6.7–8.3 · Excessively Drained drainage
Native soil is well-suited to most vegetables and herbs with regular compost additions.
Watering Needs
Drought stress: 7.5/10
High drought stress. Consistent irrigation is essential — consider drip systems, heavy mulch, and drought-tolerant varieties.
Season Tips
114-day frost-free season
A short season means indoor starts are critical for warm-season crops. Prioritise cold-hardy, fast-maturing varieties and use row covers to extend autumn harvests.
Free Garden Planner
Plan your entire garden season — organize planting dates, track what you're growing, and know exactly when to start seeds, transplant, and harvest.
Recommended for Your Garden
Test your soil pH, nitrogen, phosphorus, and potassium levels before planting.
Get instant, accurate soil pH readings to fine-tune your amendments.
Boost soil fertility and structure with rich, well-aged organic compost.
🥬 Vegetables to Grow in Grand County
96 vegetables that grow well in Zone 4a with planting dates for Grand County.
Show all 96 vegetables with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Acorn Squash | Apr 16 | Jun 11 | Jun 18 | Sep 10 – Oct 15 | 80–100 |
| Amaranth | Mar 26 | Jun 11 | Jun 18 | Sep 17 – Nov 5 | 90–120 |
| Arugula | Apr 16 | May 21 | May 28 | Jul 2 – Sep 3 | 30–50 |
| Asparagus | — | — | Jun 11 | — | 730–1095 |
| Beets | — | May 21 | — | Jul 16 – Aug 13 | 50–70 |
| Belgian Endive | Apr 16 | May 21 | May 28 | Sep 17 – Oct 22 | 110–150 |
| Black Beans | — | Jun 11 | — | Sep 10 – Oct 29 | 90–120 |
| Bok Choy | Apr 16 | May 21 | May 28 | Jul 9 – Aug 13 | 40–60 |
| Broccoli | Apr 16 | May 21 | May 28 | Jul 30 – Sep 10 | 60–90 |
| Broccoli Rabe | Apr 16 | May 21 | May 28 | Jul 9 – Aug 13 | 40–60 |
| Brussels Sprouts | Apr 16 | May 21 | May 28 | Aug 27 – Oct 22 | 90–130 |
| Butternut Squash | Apr 16 | Jun 11 | Jun 18 | Sep 17 – Oct 22 | 85–110 |
| Cabbage | Apr 16 | May 21 | May 28 | Jul 30 – Sep 24 | 60–100 |
| Carrots | — | May 21 | — | Jul 23 – Aug 27 | 60–80 |
| Cauliflower | Apr 16 | May 21 | May 28 | Jul 23 – Sep 24 | 55–100 |
| Celeriac | Apr 16 | May 21 | May 28 | Sep 10 – Oct 15 | 100–120 |
| Celery | Apr 16 | May 21 | May 28 | Aug 20 – Oct 15 | 80–120 |
| Celtuce | Apr 16 | May 21 | May 28 | Jul 30 – Sep 10 | 60–90 |
| Chard | Apr 16 | May 21 | May 28 | Jul 23 – Sep 10 | 50–60 |
| Chickpeas | Apr 16 | May 21 | May 28 | Aug 20 – Oct 1 | 80–110 |
| Chicory | Apr 16 | May 21 | May 28 | Jul 30 – Sep 10 | 60–85 |
| Chinese Cabbage | Apr 16 | May 21 | May 28 | Jul 23 – Aug 20 | 50–70 |
| Christmas Lima Beans | Mar 26 | Jun 11 | Jun 18 | Sep 10 – Oct 15 | 80–100 |
| Collard Greens | Apr 16 | May 21 | May 28 | Jul 23 – Sep 24 | 55–75 |
| Corn | — | Jun 11 | — | Aug 13 – Oct 8 | 60–100 |
| Cress | Apr 16 | May 21 | May 28 | Jun 11 – Jul 2 | 14–21 |
| Crookneck Squash | Apr 16 | Jun 11 | Jun 18 | Aug 6 – Sep 3 | 45–60 |
| Crosne | — | May 21 | — | Oct 22 – Oct 15 | 150–200 |
| Cucumber | Apr 16 | Jun 11 | Jun 18 | Aug 13 – Oct 8 | 50–70 |
| Daikon | — | May 21 | — | Jul 16 – Aug 13 | 50–70 |
| Delicata Squash | Apr 16 | Jun 11 | Jun 18 | Sep 10 – Oct 15 | 80–100 |
| Edamame | — | Jun 11 | — | Aug 27 – Oct 8 | 75–100 |
| Endive | Apr 16 | May 21 | May 28 | Jul 16 – Aug 20 | 45–65 |
| Escarole | Apr 16 | May 21 | May 28 | Jul 23 – Aug 20 | 50–70 |
| Fava Beans | Apr 16 | May 21 | May 28 | Aug 13 – Sep 24 | 75–100 |
| Fennel | Mar 26 | Jun 11 | Jun 18 | Aug 20 – Oct 1 | 60–90 |
| Garlic | — | — | — | — | 90–240 |
| Green Beans | — | Jun 11 | — | Aug 6 – Oct 1 | 50–65 |
| Horseradish | — | — | Jun 11 | Oct 15 – Nov 5 | 120–180 |
| Hubbard Squash | Apr 16 | Jun 11 | Jun 18 | Oct 1 – Nov 5 | 100–120 |
| Kabocha | Apr 16 | Jun 11 | Jun 18 | Sep 17 – Oct 15 | 85–100 |
| Kai Lan | Apr 16 | May 21 | May 28 | Jul 16 – Aug 13 | 45–60 |
| Kale | Apr 16 | May 21 | May 28 | Jul 23 – Sep 17 | 50–70 |
| Kidney Beans | — | Jun 11 | — | Sep 10 – Oct 15 | 85–110 |
| Kohlrabi | Apr 16 | May 21 | May 28 | Jul 16 – Aug 20 | 45–65 |
| Komatsuna | Apr 16 | May 21 | May 28 | Jul 2 – Aug 6 | 35–50 |
| Leeks | Apr 16 | May 21 | May 28 | Aug 27 – Oct 22 | 90–150 |
| Lentils | Apr 16 | May 21 | May 28 | Aug 20 – Oct 1 | 80–110 |
| Lettuce | Apr 16 | May 21 | May 28 | Jul 2 – Sep 10 | 30–60 |
| Lima Beans | — | Jun 11 | — | Aug 13 – Sep 24 | 60–90 |
| Mache | Apr 16 | May 21 | May 28 | Jul 9 – Aug 13 | 40–60 |
| Melon | Apr 16 | Jun 11 | Jun 18 | Aug 27 – Oct 15 | 70–100 |
| Microgreens | Apr 16 | May 21 | May 28 | Jun 4 – Jul 2 | 7–21 |
| Mitsuba | Apr 16 | May 21 | May 21 | Jul 16 – Sep 10 | 50–70 |
| Mizuna | Apr 16 | May 21 | May 28 | Jul 2 – Jul 30 | 30–45 |
| Mustard Greens | Apr 16 | May 21 | May 28 | Jul 2 – Sep 3 | 30–50 |
| Napa Cabbage | Apr 16 | May 21 | May 28 | Jul 23 – Aug 27 | 55–75 |
| Onion | Apr 16 | May 21 | May 28 | Aug 27 – Oct 15 | 90–120 |
| Pac Choi | Apr 16 | May 21 | May 28 | Jul 9 – Aug 6 | 40–55 |
| Parsnip | — | May 21 | — | Sep 3 – Oct 15 | 100–130 |
| Patty Pan Squash | Apr 16 | Jun 11 | Jun 18 | Aug 6 – Sep 3 | 45–60 |
| Peas | Apr 16 | May 21 | May 28 | Jul 23 – Sep 17 | 55–70 |
| Peppers | Mar 12 | Jun 11 | Jun 18 | Aug 20 – Oct 29 | 60–90 |
| Pole Beans | Mar 26 | Jun 11 | Jun 18 | Aug 13 – Oct 8 | 55–70 |
| Potatoes | Mar 26 | Jun 11 | Jun 18 | Aug 27 – Nov 5 | 70–120 |
| Pumpkin | Apr 16 | Jun 11 | Jun 18 | Sep 17 – Nov 5 | 85–120 |
| Purslane | Apr 16 | May 21 | May 28 | Jul 9 – Aug 13 | 40–60 |
| Radicchio | Apr 16 | May 21 | May 28 | Jul 30 – Sep 3 | 60–80 |
| Radish | — | May 21 | — | Jun 18 – Jul 9 | 22–35 |
| Rhubarb | — | — | Jun 25 | — | 365–730 |
| Romanesco | Apr 16 | May 21 | May 28 | Aug 13 – Sep 24 | 75–100 |
| Rutabaga | — | May 21 | — | Aug 13 – Sep 17 | 80–100 |
| Salsify | — | May 21 | — | Sep 3 – Oct 15 | 100–130 |
| Savoy Cabbage | Apr 16 | May 21 | May 28 | Aug 6 – Oct 1 | 70–110 |
| Scallions | Apr 16 | May 21 | May 28 | Jul 23 – Aug 20 | 50–70 |
| Scarlet Runner Beans | Mar 26 | Jun 11 | Jun 18 | Aug 20 – Sep 24 | 60–80 |
| Shallot | Apr 16 | May 21 | May 28 | Aug 27 – Oct 15 | 90–120 |
| Shiso | Apr 2 | Jun 4 | Jun 18 | Aug 13 – Oct 8 | 50–70 |
| Snap Peas | Mar 26 | Jun 11 | Jun 18 | Aug 13 – Oct 8 | 55–70 |
| Snow Peas | Apr 16 | May 21 | May 28 | Jul 23 – Sep 17 | 50–65 |
| Soybeans | — | Jun 11 | — | Sep 3 – Oct 29 | 80–120 |
| Spaghetti Squash | Apr 16 | Jun 11 | Jun 18 | Sep 17 – Oct 15 | 85–100 |
| Spinach | Apr 16 | May 21 | May 28 | Jul 2 – Sep 3 | 35–50 |
| Squash (Summer) | Apr 16 | Jun 11 | Jun 18 | Aug 6 – Oct 8 | 45–65 |
| Squash (Winter) | Apr 16 | Jun 11 | Jun 18 | Sep 10 – Nov 5 | 80–120 |
| Sunchoke | — | — | Jun 11 | Oct 1 – Nov 5 | 110–150 |
| Sunflower | Mar 26 | Jun 11 | Jun 18 | Aug 27 – Oct 15 | 70–100 |
| Sweet Corn | — | Jun 11 | — | Aug 13 – Sep 24 | 60–90 |
| Tatsoi | Apr 16 | May 21 | May 28 | Jul 2 – Aug 6 | 35–50 |
| Tomatillo | Mar 26 | Jun 11 | Jun 18 | Aug 20 – Oct 29 | 60–85 |
| Tomatoes | Mar 26 | Jun 11 | Jun 18 | Aug 20 – Oct 29 | 60–85 |
| Turnip | — | May 21 | — | Jul 2 – Aug 6 | 40–60 |
| Watercress | Apr 16 | May 21 | May 28 | Jul 9 – Aug 13 | 40–60 |
| Watermelon | Apr 16 | Jun 11 | Jun 18 | Aug 27 – Oct 15 | 70–100 |
| Wax Beans | — | Jun 11 | — | Aug 6 – Oct 1 | 50–65 |
| Zucchini | Apr 16 | Jun 11 | Jun 18 | Aug 6 – Oct 1 | 45–60 |
🍓 Fruits to Grow in Grand County
22 fruits that grow well in Zone 4a with planting dates for Grand County.
Show all 22 fruits with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Alpine Strawberries | — | — | Jun 25 | Sep 24 – Nov 19 | 90–180 |
| Aronia | — | — | Jun 25 | — | 730–1095 |
| Blueberries | — | — | Jun 25 | — | 730–1095 |
| Cantaloupe | — | — | Jun 25 | Sep 3 – Oct 8 | 70–90 |
| Cranberries | — | — | Jun 25 | — | 730–1095 |
| Currants | — | — | Jun 25 | — | 730–1095 |
| Elderberries | — | — | Jun 25 | — | 730–1095 |
| Goji Berries | — | — | Jun 25 | — | 730–1095 |
| Gooseberries | — | — | Jun 25 | — | 730–1095 |
| Grapes | — | — | Jun 25 | — | 730–1095 |
| Ground Cherry | — | — | Jun 25 | Sep 3 – Oct 29 | 65–80 |
| Hardy Kiwi | — | — | Jun 25 | — | 1095–1825 |
| Haskaps | — | — | Jun 25 | — | 730–1095 |
| Honeydew | — | — | Jun 25 | Sep 17 – Oct 29 | 80–110 |
| Jostaberry | — | — | Jun 25 | — | 730–1095 |
| Lingonberries | — | — | Jun 25 | — | 730–1095 |
| Medlar | — | — | Jun 25 | — | 1095–1825 |
| Mulberries | — | — | Jun 25 | — | 730–1825 |
| Persimmon | — | — | Jun 25 | — | 1095–2555 |
| Raspberries | — | — | Jun 25 | — | 365–730 |
| Serviceberries | — | — | Jun 25 | — | 730–1095 |
| Strawberries | — | — | Jun 25 | Sep 24 – Nov 19 | 90–365 |
🌿 Herbs to Grow in Grand County
32 herbs that grow well in Zone 4a with planting dates for Grand County.
Show all 32 herbs with planting dates
| Plant | Start Indoors | Direct Sow | Transplant | Harvest | Days to Maturity |
|---|---|---|---|---|---|
| Angelica | Apr 16 | May 21 | May 21 | — | 365–730 |
| Anise | Apr 16 | May 21 | May 21 | Aug 20 – Oct 15 | 90–120 |
| Basil | Apr 2 | Jun 4 | Jun 18 | Aug 13 – Oct 15 | 50–75 |
| Bee Balm | — | — | Jun 4 | Sep 3 – Oct 29 | 90–120 |
| Borage | Apr 16 | May 21 | May 21 | Jul 16 – Sep 3 | 50–60 |
| Caraway | Apr 16 | May 21 | May 21 | — | 365–450 |
| Catnip | — | — | Jun 4 | Aug 6 – Oct 8 | 60–80 |
| Chamomile | Apr 16 | May 21 | May 21 | Jul 23 – Oct 1 | 60–90 |
| Chervil | Apr 16 | May 21 | May 21 | Jul 2 – Sep 3 | 40–60 |
| Chives | — | — | Jun 4 | Aug 6 – Oct 15 | 60–90 |
| Cilantro | Apr 16 | May 21 | May 21 | Jul 2 – Sep 3 | 40–60 |
| Comfrey | — | — | Jun 4 | Aug 6 – Oct 15 | 60–90 |
| Dill | Apr 16 | May 21 | May 21 | Jul 2 – Sep 3 | 40–60 |
| Echinacea | — | — | Jun 4 | Oct 8 – Oct 29 | 120–180 |
| Fennel (herb) | Apr 16 | May 21 | May 21 | Jul 23 – Oct 1 | 60–90 |
| Garlic Chives | — | — | Jun 4 | Aug 6 – Oct 15 | 60–90 |
| Horehound | — | — | Jun 4 | Aug 20 – Oct 15 | 75–90 |
| Hyssop | — | — | Jun 4 | Aug 13 – Oct 15 | 70–90 |
| Lemon Balm | — | — | Jun 4 | Aug 6 – Sep 24 | 60–70 |
| Lovage | — | — | Jun 4 | Aug 13 – Oct 15 | 70–90 |
| Mint | — | — | Jun 4 | Aug 6 – Oct 15 | 60–90 |
| Oregano | — | — | Jun 4 | Aug 6 – Oct 15 | 60–90 |
| Parsley | Apr 16 | May 21 | May 21 | Jul 23 – Sep 24 | 60–80 |
| Rue | — | — | Jun 4 | Aug 13 – Oct 15 | 70–90 |
| Sage | — | — | Jun 4 | Aug 20 – Oct 15 | 75–90 |
| Savory | — | — | Jun 4 | Jul 30 – Sep 24 | 50–70 |
| Sorrel | Apr 16 | May 21 | May 21 | Jul 2 – Sep 3 | 40–60 |
| Tarragon | — | — | Jun 4 | Aug 6 – Oct 15 | 60–90 |
| Thai Basil | Apr 2 | Jun 4 | Jun 18 | Aug 13 – Oct 15 | 50–75 |
| Thyme | — | — | Jun 4 | Aug 13 – Oct 15 | 70–90 |
| Valerian | — | — | Jun 4 | Oct 8 – Oct 29 | 120–180 |
| Yarrow | — | — | Jun 4 | Sep 3 – Oct 29 | 90–120 |
Monthly Planting Guide for Grand County
Gardening Guides & Resources
Helpful guides from The Ultimate Homestead to improve your garden in Grand County.
Frequently Asked Questions
What planting zone is Grand County, CO?
Grand County is in USDA Hardiness Zone 4a. This zone classification determines which perennial plants survive winter and sets the baseline for frost timing across the county.
When is the last frost in Grand County, CO?
Based on 31 years of NOAA weather station data, the median last spring frost in Grand County falls around May 28. In 8 out of 10 years, last frost lands between April 29 and June 18 — a 49-day window of variability. Use June 18 as your conservative safe-to-plant date for frost-sensitive crops.
When is the first fall frost in Grand County, CO?
The median first fall frost in Grand County arrives around September 19. In cold years it can arrive as early as September 3; in mild years as late as October 13. Harvest or protect frost-sensitive crops — tomatoes, peppers, basil, squash — before this date.
How long is the growing season in Grand County?
Grand County has a frost-free growing season of approximately 114 days. Focus on short-season varieties and start warm-season crops indoors 6–8 weeks before last frost. Climate records show the growing season is trending longer by about 2.73 days per decade.
What is the soil like in Grand County for gardening?
Grand County has predominantly Loam soil with a pH range of 6.7–8.3 and Excessively Drained drainage. Most vegetables and herbs grow well with standard composting and seasonal soil amendment.
What is grown commercially in Grand County?
Grand County has commercial agriculture that includes Cattle, Hay, Wheat. These crops reflect the local climate and soil conditions — what succeeds commercially often translates well to home gardens in the same area.
Is Grand County a good location for home gardening?
Grand County scores 33/100 (Challenging) on our Microclimate Index, which combines frost reliability, drought pressure, soil challenge, elevation risk, and long-term climate trend. Gardening here benefits from close attention to frost timing and season extension due to the challenging microclimate factors.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Grand County gardeners in Zone 4a organize planting dates, track what's growing, and never miss a planting window.
Get Your Free Garden Planner →Free download. Plan your entire garden season in minutes.
