When to Plant Eggplant in Idaho
Beautiful purple fruits that love heat even more than tomatoes. Start early indoors for best results.
The Short Answer
Idaho Frost Dates
Your planting dates depend on which part of Idaho you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Northern Idaho | 5a, 5b, 6a | May 5 - May 25 | Sep 15 - Oct 5 |
| Boise Area | 6b, 7a | Apr 20 - May 5 | Oct 5 - Oct 20 |
| Eastern Idaho | 3b, 4a, 4b, 5a | May 20 - Jun 10 | Sep 1 - Sep 20 |
Eggplant Planting Schedule for Idaho
Northern Idaho (Zones 5a, 5b, 6a)
Average last frost: May 5 - May 25 · Average first frost: Sep 15 - Oct 5
Boise Area (Zones 6b, 7a)
Average last frost: Apr 20 - May 5 · Average first frost: Oct 5 - Oct 20
Eastern Idaho (Zones 3b, 4a, 4b, 5a)
Average last frost: May 20 - Jun 10 · Average first frost: Sep 1 - Sep 20
Growing Eggplant in Idaho
Eggplant in Idaho's Climate
Eggplant is one of the trickiest warm-season crops for cold climates — it demands even more heat than peppers. Asian varieties (Ichiban, Orient Express, 55-58 days) are the only reliable choice. Start indoors 10 weeks before last frost. Black plastic mulch and row cover are both necessary. Container growing on sun-baked pavement sometimes outproduces in-ground planting.
Soil Considerations for Idaho
Volcanic ash soils in south — excellent for gardening. Rocky soils in mountains. Alkaline in many areas. Make sure soil has warmed to at least 70°F before planting eggplant outside.
Idaho Climate & Growing Season
Arid climate. Low humidity. Hot days and cool nights. Irrigation essential. Short season at higher elevations. Eggplant cannot tolerate any frost, so wait until all frost danger has passed before transplanting outside. Watch local forecasts carefully in spring.
Growing season length varies across Idaho: Northern Idaho (5a, 5b, 6a) has a last frost around May 5 - May 25, while Eastern Idaho (3b, 4a, 4b, 5a) sees frost end around May 20 - Jun 10. This difference matters for eggplant — transplant timing shifts by several weeks across the state.
Growing Tips
Harvest when skin is glossy and firm. Dull skin means overripe and seedy. Use row covers if nights are cool.
Companion Planting
Plant eggplant alongside these companions for better growth:
Keep eggplant away from:
The Bottom Line
Last reviewed: March 29, 2026