When to Plant Eggplant in Washington County, IA
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.
Washington County, Iowa is in USDA Zone 5a. The average last spring frost is April 21 and the first fall frost is October 14, giving you a growing season of approximately 176 days.
At an elevation of 542 feet, Washington County receives approximately 30.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 83°F, so choose short-season varieties of Eggplant to ensure they mature before fall.
Washington County Soil Profile
Soil Type
Silt Loam
Soil pH
5.9-6.7
Drainage
Well Drained
Plant 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 Washington County
How your county's soil matches Eggplant's growing requirements.
Soil pH
Your soil pH (5.9–6.7) is within Eggplant's preferred range (5.5–7.0).
Soil Texture
The silt loam soil in Washington County is excellent for Eggplant — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (5.0%) — Eggplant will thrive.
How to Plant Eggplant
Succession Planting Eggplant
Sow every 7.4 weeks. Last sowing by Jul 21 to harvest before frost.
Plant 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 | — | 1.2" | 0" | ❄️ Dormant |
| Feb | — | 1.5" | 0" | ❄️ Dormant |
| Mar | — | 1.9" | 0" | ❄️ Dormant |
| Apr | 4.8" | 3.4" | 1.4" | 💧 Light watering |
| May | 4.8" | 3.2" | 1.6" | 💧 Light watering |
| Jun | 4.8" | 3.4" | 1.4" | 💧 Light watering |
| Jul | 4.8" | 3.8" | 1" | 💧 Light watering |
| Aug | 4.8" | 3.2" | 1.6" | 💧 Light watering |
| Sep | 4.8" | 2.6" | 2.2" | 💧 Light watering |
| Oct | 4.8" | 2.6" | 2.2" | 💧 Light watering |
| Nov | — | 2" | 0" | ❄️ Dormant |
| Dec | — | 1.7" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Washington 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 — Washington County, IA
Eggplant Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 10 | Feb 10 – Feb 24 |
| Transplant Outdoors | May 5 | May 5 – May 19 |
| Direct Sow | April 28 | Apr 28 – May 19 |
| Harvest | July 14 | Jul 14 – Sep 15 |
Plant 1" deep · 30" apart · Rows 42" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | — |
| April | Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1.1"/week · 1-2 times/week
📅 Days to Maturity
65–85 days
🧪 Soil pH
Needs 5.5–7 · Your soil: ideal
🗺️ USDA Zone
Zone 5a
📆 Growing Season
176 days in Washington County
Growing Tips for Eggplant in Washington County
Direct sow Eggplant outdoors after April 21 in Washington 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.
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 Washington County, IA?
Washington County is in Zone 5a with an average last frost of April 21. Plan your Eggplant planting based on this frost date — see the calendar above for exact timing.
What planting zone is Washington County, IA?
Washington County, Iowa is in USDA Hardiness Zone 5a. The average last spring frost is April 21 and first fall frost is October 14.
Plan Your Garden with Confidence
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