When to Plant Zucchini in Washington, DC
Published: April 21, 2026
Zucchini Planting Dates for Washington, DC
| Start seeds indoors | March 1–8 |
| Last frost (average) | March 22 |
| Transplant outdoors | March 29–April 8 |
| Direct sow outdoors | March 29–April 8 |
| Minimum soil temperature | 65°F |
| Expect first harvest | May 13 – May 23 |
| Fall crop planting | September 15–25 |
| Fall crop harvest | October 30 |
| First fall frost (average) | November 10 |
Best Zucchini Varieties for Washington, DC
For Zone 6b Washington, the best-performing zucchini varieties are Black Beauty, Patio Star, and Golden Egg — all widely adapted, disease-resistant varieties proven across the transition zone. Astia is a good alternative where disease resistance matters most, especially in humid summers. These varieties are typically stocked by local nurseries and are the safest bets for gardeners new to zucchini in Washington.
Growing Zucchini in Washington
Washington sits in Zone 6b, with an average last frost of March 22 and first fall frost around November 10 — giving a 233-day frost-free growing season. Warm-season crops like zucchini need soil at 65°F or above before transplanting; Washington's frost calendar puts that window clearly in the late-spring to early-fall range.
Washington's moderate climate supports zucchini on the standard transplant calendar with minimal special accommodation. Succession planting — sowing fresh seeds or setting new transplants every 2–3 weeks through spring — stretches the harvest window and gives you a backup crop if pests hit the first planting.
Washington's mixed soil conditions vary block by block — get a soil test if you have not in three years. Generally, a base of quality compost (2 to 3 inches annually) and consistent watering at 2 inches per week serves zucchini well across most soil types found in Washington.
Zucchini Calendar for Washington
| Month | Task |
|---|---|
| March | Start seeds indoors under grow lights |
| March | Transplant outdoors into warm soil |
| May | Expect first harvest window to open |
| September | Start fall crop — transplants or direct sow |
| November | First fall frost — harvest remaining, end of outdoor season |
Zucchini Tips for Washington Gardeners
- •Start with just 1–2 plants — zucchini are so productive that more is rarely needed.
- •Harvest at 6–8 inches for peak flavor; zucchini left on the plant signals it to stop producing.
- •Succession plant zucchini in Washington every 2–3 weeks through spring to extend the harvest window into summer.
Common Zucchini Pests in Washington
- •Squash Vine Borer — peaks July in Zone 6b (active May–September); sudden wilting with frass at stem base; inject Bt into the stem or use row covers through flowering.
- •Squash Bug — peaks July in Zone 6b (active May–September); gray-brown shield bugs that suck plant sap; handpick and destroy egg clusters on leaf undersides.
- •Powdery Mildew — peaks July in Zone 6b (active May–September); white powdery coating on leaves; improve airflow and apply milk spray (1:9 milk-to-water).
Check plants every 2–3 days during peak season — early intervention prevents most infestations from becoming serious.
What to Plant with Zucchini in Washington
In Washington's moderate climate, Corn and Bush Beans are the most beneficial plants to grow alongside zucchini. Corn provides vertical support for climbing companions in the Three Sisters planting. Keep zucchini away from Potato — it competes for nutrients and shares blight diseases.
Frequently Asked Questions
When should I plant zucchini in Washington, DC?
In Washington (Zone 6b), start zucchini seeds indoors around March 1–8 and transplant outdoors around March 29–April 8. The city's average last frost of March 22 is the anchor date — count 3 weeks back for seed starting and 1 weeks forward for transplanting.
What zone is Washington, DC for zucchini growing?
Washington is USDA Zone 6b. For zucchini, this means a frost-free growing season of roughly 33 weeks running from March 22 to November 10. This is a comfortable window for warm-season crops like zucchini — standard varieties work well.
When is zucchini harvest season in Washington?
Expect the first zucchini harvest in Washington around May 13, with harvest continuing through May 23. This is based on 45–55 days from transplant or direct sow. A fall crop planted September 15–25 adds a second harvest around October 30.
How long does it take to grow zucchini in Washington, DC?
From transplant or direct sow to first harvest, zucchini takes 45–55 days in Washington's climate. Based on a typical planting date of March 29–April 8, expect your first harvest around May 13. Washington's Zone 6b transition-zone climate produces maturity times right in the middle of the stated range.
What soil does zucchini need in Washington?
Washington's soil conditions vary block by block. Before planting zucchini, do a soil test (most state extension offices run them for $15–30). The test reveals pH, key nutrient levels, and organic matter content, so you can amend appropriately rather than guessing. Generally, 2–3 inches of compost annually improves most soils for vegetable production.