What to Plant in March — Zone 3

March ends about 6 weeks before zone 3's average last frost (May 15) — prime seed-starting territory.

Start seeds indoors — Counted back from the last frost so transplants are ready on time.

🥬 Cabbage	Mar 20 – Apr 3	65–85 days to maturity
🥦 Broccoli	Mar 27 – Apr 10	60–75 days to maturity
🥦 Cauliflower	Mar 27 – Apr 10	60–80 days to maturity
🧅 Onions	Mar 6 – Mar 20	90–110 days to maturity
🧅 Leeks	Mar 6 – Mar 20	100–120 days to maturity
🥬 Celery	Mar 6 – Mar 20	100–120 days to maturity
🍅 Tomatoes	Mar 20 – Apr 3	60–85 days to maturity
🫑 Peppers	Mar 6 – Mar 20	60–90 days to maturity
🍆 Eggplant	Mar 6 – Mar 20	65–80 days to maturity
🍏 Tomatillos	Mar 20 – Apr 3	70–80 days to maturity
🌿 Parsley	Mar 6 – Mar 20	70–90 days to maturity
🌱 Chives	Mar 20 – Apr 3	75–85 days to maturity
🌿 Thyme	Mar 6 – Mar 20	90–120 days to maturity
🌿 Oregano	Mar 20 – Apr 3	80–90 days to maturity

Windows use zone 3's typical frost dates (May 15 / Sep 20). For your own city's dates, run the frost lookup — the planting calendar then localizes everything automatically.

Frequently asked questions

What can I plant outside in March in zone 3?

Nothing goes outside yet in zone 3 — March is for starting seeds indoors (cabbage, broccoli, cauliflower, onions, leeks, celery, tomatoes, peppers, and 6 more). Outdoor planting opens closer to the May 15 average last frost.

What seeds should I start indoors in March in zone 3?

Cabbage, broccoli, cauliflower, onions, leeks, celery, tomatoes, peppers, and 6 more — each is counted back from zone 3's average last frost around May 15, so transplants are ready exactly when the garden is.

Is March the right time for tomatoes in zone 3?

For seed-starting, yes: sow indoors Mar 20 – Apr 3. Transplanting waits until after the May 15 average last frost.