🧅 Can I Plant Onion in Knoxville, TN?

2026 planting guide for Zone 7a · Last frost ~April 3 · Growing season ~211 days

✅ YES — Good temps, but watch for heat — highs near 88°F

Temperature conditions are suitable for Onion. Highs near 88°F are on the warm side — make sure plants have plenty of water.

Planting window: May 18 – Jun 1
Good to go — plant now while conditions are right.
Live result based on current forecast for Knoxville, TN · Updates every 6 hours
USDA Zone
7a
Last Spring Frost
~April 3
First Fall Frost
October 31
Growing Season
~211 days
Ideal Temp for Onion
45–75°F
Frost Risk
✅ Tolerant

Growing Onion in Knoxville

Knoxville's Zone 7a location in the Tennessee Valley between the Great Smokies and the Cumberland Plateau provides about 211 frost-free days. The valley climate is warm and humid in summer — productive for tomatoes, peppers, beans, and squash. Spring and fall are especially rewarding, with cool-season crops planted in August delivering excellent harvests through November. The mountain backdrop creates interesting microclimate variation across the area.

In Knoxville (last frost around April 3), onion can go out around February — approximately 6 weeks before the last expected frost, making it an early-season opportunity. Starting seeds indoors 10 weeks before the last frost date gives you a significant head start.

Onion thrives between 45°F and 75°F. It tolerates temperatures as low as 28°F, making it a candidate for early spring planting before the last frost date. Expect 100–120 days from transplant to first harvest. Long season. Start early indoors or use sets.

Frequently Asked Questions

When can I plant onion in Knoxville, TN?

In Knoxville (last frost around April 3), onion can go out around February — approximately 6 weeks before the last expected frost, making it an early-season opportunity. For best results, start seeds indoors 10 weeks before that — giving you strong transplants ready to go out at the right time.

What is the USDA hardiness zone for Knoxville?

Knoxville, TN is in USDA Plant Hardiness Zone 7a. The last expected spring frost is around April 3, and the first fall frost arrives around October 31. This zone classification helps you understand which perennials survive winter and when annual vegetables can safely go outdoors.

Is it safe to plant onion outside in Knoxville right now?

That depends on the current weather forecast. Onion needs temperatures above 28°F (ideally 45–75°F) to thrive. CanIPlant checks your real 7-day forecast and any active frost alerts to give you a live YES, NO, or WAIT answer — just enter your ZIP code.

Can I grow onion in Knoxville 2026?

Yes — Onion grows well in Knoxville, TN. With a Zone 7a climate and a growing season of ~211 days, Knoxville is well-suited for cool-season crops like onion. As a frost-tolerant crop, onion can even go out a few weeks before the last frost date.

Grow Onion in Other Cities

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