When to Plant Eggplant in Washington
Published: April 24, 2026
Washington gardeners in Zone 4b have a 21-week frost-free window for eggplant (May 7 to October 1). Warm-season crops like eggplant must be started indoors early to maximize the short window — Washington's late spring and early fall frost dates leave little room for error. This guide gives exact dates for Washington based on your local frost calendar.
Eggplant Planting Dates for Washington
| Start seeds indoors | March 5–12 |
| Last frost (average) | May 7 |
| Transplant outdoors | May 28–June 7 |
| Expect first harvest | August 1 – August 16 |
| First fall frost (average) | October 1 |
⚠ Start eggplant indoors 8–10 weeks before last frost — same timing as peppers. Transplant 2–3 weeks after last frost when soil is above 60°F. Needs heat and full sun. Does not tolerate cold — protect from temps below 50°F.
Growing Eggplant in Washington's Climate
Washington's cold Zone 4b climate puts warm-season eggplant at the edge of viability — but the edge is workable with good planning. Starting seeds indoors under lights in late winter is the most important step; skipping this puts the whole harvest at risk from the short outdoor growing window.
Season extenders pay for themselves many times over in Washington. Row covers placed over transplants in early spring add 5°F to 8°F of protection and can extend the season two to three weeks on each end. Black plastic mulch warms the soil to the temperatures eggplant needs for aggressive root growth.
Common eggplant pests to watch for in Washington include Flea Beetle and Colorado Potato Beetle. The first line of defense is companion planting: Pepper and Bean planted nearby discourage several of these pests by confusing host-plant identification or repelling adults before they can lay eggs. Weekly garden walks in the early morning catch problems when they're still manageable.
Eggplant Garden Calendar for Washington
| Month | Task | Notes |
|---|---|---|
| January | — | Dormant season |
| February | — | Dormant season |
| March | Start seeds indoors | Use grow lights; warm soil to 70–75°F for best germination |
| April | — | Dormant season |
| May ← | Transplant outdoors | Soil temp must be 60°F+; nighttime lows above 50°F |
| June | Peak growth; water 1 inch/week | Monitor for pests daily; stake or support as needed |
| July | Continue care | Consistent watering; remove yellow leaves |
| August | First harvest window opens | Eggplant begins producing 65–80 days after transplant |
| September | — | Dormant season |
| October | First frost approaches | Harvest remaining eggplant; cover plants on frost nights |
| November | — | Dormant season |
| December | — | Dormant season |
Eggplant Growing Tips for Washington Gardeners
- •Use a heat mat during germination — eggplant seeds need 24–27°C soil to sprout reliably.
- •Protect transplants from cold spring nights — temperatures below 10°C halt growth for weeks.
- •Washington's short growing season means start seeds indoors under grow lights — don't rely on windowsill light which produces leggy, weak seedlings that struggle outdoors.
- •Cover young transplants with floating row covers for the first 2–3 weeks outside. The 3–5°F of protection reduces frost damage risk and accelerates early growth.
- •Use stakes or small cages — eggplant stems bend or break under the weight of mature fruit.
Companion Planting for Eggplant in Washington
In Washington's cold climate, planting eggplant with Pepper and Bean helps deter pests and improve soil. Avoid planting near Fennel and Brassicas, which inhibit eggplant growth through root chemistry or shared pest pressure. See the full eggplant companion planting guide for the complete list.
Eggplant Planting Dates by City in Washington
Top cities in Washington — select for city-level frost dates and planting calendars.
Frequently Asked Questions
When should I plant eggplant in Washington?
In Washington (Zone 4b), start eggplant seeds indoors around March 5–12 and transplant outdoors around May 28–June 7 — 3 weeks after the state's average last frost of May 7.
What is the last frost date in Washington?
Washington's average last frost date is May 7 in the state's most common Zone 4b. Frost dates vary by city — higher elevations and northern counties run 1 to 3 weeks later than the state average. See the city list below for city-level frost dates.
Can I grow eggplant year-round in Washington?
Not year-round — Washington's cold season stops eggplant production. The eggplant season runs May 7 to October 1, roughly 21 weeks.
What eggplant varieties grow best in Washington?
For Washington's Zone 4b, consult a local nursery or extension office for eggplant variety recommendations.
When do I start eggplant seeds indoors in Washington?
Start eggplant seeds indoors in Washington around March 5–12, which is 9 weeks before the state's average last frost of May 7. Use grow lights and keep soil temperatures at 70–75°F for fastest germination.