When to plant Eggplant in Boulder County, CO
In Boulder County, Eggplant is a single-season spring crop — there's no second fall window. Plant May 21–June 11 for an 65–85-day harvest, finishing well before the September 26 first frost.
When to Plant Eggplant in Boulder County, CO
Your June gardening checklist
June is a pivotal month for Boulder County, Colorado gardens. Focus on these tasks first and you'll set up the rest of the season for success.
July prep starts now
- Starting indoors: eggplant
Eggplant is a heat-loving solanaceous crop that produces glossy fruits in purple, white, or striped varieties. It requires long, warm growing seasons for best production.
Boulder County, Colorado is in USDA Zone 6a. The average last spring frost is May 14 and the first fall frost is September 26, giving you a growing season of approximately 135 days.
At an elevation of 7,657 feet, Boulder County receives approximately 22.2 inches of rainfall annually with predominantly loam soil. Summer highs average 86°F, providing good warmth for Eggplant during the growing season.
Boulder County Soil Profile
Soil Type
Loam
Soil pH
6.7-8
Drainage
Well Drained
Eggplant Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
Soil Compatibility in Boulder County
How your county's soil matches Eggplant's growing requirements.
Soil pH
Your soil pH (6.7–8.0) is more alkaline than Eggplant prefers (5.5–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Boulder County is excellent for Eggplant — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Eggplant.
Organic Matter
Organic matter is moderate (2.3%). Annual compost additions will help Eggplant.
How to Plant Eggplant
Succession Planting Eggplant
Sow every 7.4 weeks. Last sowing by Jul 03 to harvest before frost.
Eggplant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Eggplant
Eggplant needs approximately 1.1 inches of water per week (4.8" per month). Here's how your county's rainfall compares month by month.
| Month | Eggplant Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.7" | 0" | ❄️ Dormant |
| Feb | — | 1.3" | 0" | ❄️ Dormant |
| Mar | — | 1.8" | 0" | ❄️ Dormant |
| Apr | — | 2.2" | 0" | ❄️ Dormant |
| May | 4.8" | 3" | 1.8" | 💧 Light watering |
| Jun | 4.8" | 1.6" | 3.2" | 🚿 Regular watering |
| Jul | 4.8" | 2" | 2.8" | 🚿 Regular watering |
| Aug | 4.8" | 2.1" | 2.7" | 🚿 Regular watering |
| Sep | 4.8" | 2.1" | 2.7" | 🚿 Regular watering |
| Oct | — | 1.9" | 0" | ❄️ Dormant |
| Nov | — | 1.4" | 0" | ❄️ Dormant |
| Dec | — | 1.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Boulder County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Eggplant Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
Eggplant Planting Timeline — Boulder County, CO
Eggplant Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 5 | Mar 5 – Mar 19 |
| Transplant Outdoors | May 28 | May 28 – Jun 11 |
| Direct Sow | May 21 | May 21 – Jun 11 |
| Harvest | August 6 | Aug 6 – Oct 8 |
Plant 1" deep · 30" apart · Rows 42" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | — |
| May | Transplant Outdoors Direct Sow |
| June | Transplant Outdoors Direct Sow |
| July | — |
| August | Harvest |
| September | Harvest |
| October | Harvest |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1.1"/week · 2-3 times/week
📅 Days to Maturity
65–85 days
🧪 Soil pH
Needs 5.5–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 6a
📆 Growing Season
135 days in Boulder County
Growing Tips for Eggplant in Boulder County
Direct sow Eggplant outdoors after May 14 in Boulder County when soil has warmed and frost danger has passed.
Common pests for Eggplant in this region include tomato hornworm and aphids. Use row covers early in the season and inspect plants weekly.
Boulder County receives only 22" of rain annually. Eggplant needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Start seeds indoors 8-10 weeks before last frost. Transplant only after nighttime temperatures stay above 55F. Mulch to retain moisture and warmth around roots.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Eggplant in Other Locations
Frequently Asked Questions
When should I plant Eggplant in Boulder County, CO?
Boulder County is in Zone 6a with an average last frost of May 14. Plan your Eggplant planting based on this frost date — see the calendar above for exact timing.
What planting zone is Boulder County, CO?
Boulder County, Colorado is in USDA Hardiness Zone 6a. The average last spring frost is May 14 and first fall frost is September 26.
When should I plant Eggplant in Boulder County, CO?
In Boulder County, CO, plant Eggplant after the last frost (around May 14) and before the first frost (around September 26). Best results when soil holds above 50°F.
What growing zone is Boulder County, CO for Eggplant?
Boulder County sits in USDA Zone 6a. Eggplant grows reliably in zones 5a through 11b, so it's a good fit here.
Can Eggplant grow in Boulder County's climate?
Yes — Eggplant grows well in Boulder County's temperate climate. Boulder County averages a 135-day frost-free season, with last frost around May 14 and first frost around September 26.
Your Boulder County Garden Planner — Free
A 22-page printable planner built for Boulder County (Zone 6a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.