What to Plant in March: A Zone-by-Zone Spring Planting Guide

March is the month that separates planners from growers. While the last frost hasn’t passed in most of the country, there’s plenty you can — and should — be doing right now. The key is knowing what works in your zone.

Understanding Your Planting Window

Your USDA hardiness zone determines your average last frost date, which is the single most important date in your spring garden. Everything revolves around it:

• Zones 8–10 (last frost: Feb or earlier) — You’re already in full planting mode
• Zones 6–7 (last frost: mid-April) — Start seeds indoors, direct sow cool crops
• Zones 3–5 (last frost: May–June) — Indoor seed starting is your main activity

If you’re not sure of your zone, garden.gg calculates it from your location and gives you personalized planting dates for every crop in your garden.

What to Direct Sow in March

These crops can handle frost and go straight into the ground in zones 6 and warmer:

Leafy Greens

• Lettuce — Germinates in cool soil (40°F+). Succession plant every 2 weeks for continuous harvests
• Spinach — Prefers cool weather. Actually bolts in heat, so March is ideal
• Kale — Frost-tolerant down to 20°F. One of the hardiest crops you can grow
• Arugula — Fast-growing (ready in 30–40 days). Perfect for impatient gardeners

Root Vegetables

• Radishes — The fastest crop in the garden (21–30 days to harvest). Great for kids and beginners
• Carrots — Slow to germinate (14–21 days) but worth the wait. Sow now for June harvests
• Beets — Dual-purpose: eat the roots and the greens. Sow seeds 1 inch apart

Alliums

• Onion sets — Plant sets (small bulbs) 1 inch deep, 4 inches apart
• Garlic (fall-planted) — If you planted in October/November, it should be sprouting now. Side-dress with nitrogen

Peas

• Snow peas, snap peas, and shelling peas — Direct sow as soon as soil is workable. They fix their own nitrogen, so skip the fertilizer

What to Start Indoors in March

For zones 5–7, March is prime time for indoor seed starting. These need 6–8 weeks indoors before transplanting after your last frost:

• Tomatoes — Start 6–8 weeks before last frost. Use a heat mat for faster germination
• Peppers — Start 8–10 weeks before last frost. Peppers are slow — don’t wait
• Eggplant — Similar timeline to peppers. Needs warm soil (70°F+) to germinate
• Broccoli & cauliflower — Start 6 weeks before last frost. Transplant when seedlings have 4–6 true leaves
• Herbs (basil, cilantro, parsley) — Basil needs warmth; parsley and cilantro prefer cool starts

Indoor Starting Tips

1. Use a seed-starting mix, not garden soil. It’s lighter and drains better
2. Bottom water to prevent damping off (a fungal disease that kills seedlings)
3. Provide 12–16 hours of light. A south-facing window often isn’t enough — supplement with grow lights
4. Harden off before transplanting. Gradually expose seedlings to outdoor conditions over 7–10 days

Zone-Specific March Planting Checklists

Zones 3–4 (Minneapolis, Anchorage)

• ✅ Start tomatoes, peppers, and eggplant indoors
• ✅ Order seeds if you haven’t already
• ✅ Plan your garden layout
• ✅ Test your soil

Zones 5–6 (Chicago, Denver, Boston)

• ✅ Start warm-season crops indoors (tomatoes, peppers)
• ✅ Direct sow peas, spinach, and radishes (late March)
• ✅ Prepare raised beds — amend soil with compost
• ✅ Set up cold frames for extra protection

Zones 7–8 (Atlanta, Dallas, Seattle)

• ✅ Direct sow most cool-season crops
• ✅ Transplant broccoli, cabbage, and cauliflower starts
• ✅ Start warm-season crops indoors
• ✅ Plant potatoes (St. Patrick’s Day is the traditional date)

Zones 9–10 (Phoenix, Miami, Los Angeles)

• ✅ Direct sow warm-season crops (beans, squash, cucumbers)
• ✅ Transplant tomato and pepper starts
• ✅ Harvest cool-season crops planted in winter
• ✅ Watch for pest pressure as temperatures rise

Common March Mistakes

Starting too early. It’s tempting to start seeds in February, but leggy, root-bound seedlings perform worse than ones started on time. Count back from your last frost date.

Skipping soil prep. Cold, compacted, waterlogged soil is the enemy. Wait until your soil passes the “squeeze test” — a handful should crumble, not form a mudball.

Forgetting succession planting. One big planting of lettuce gives you one big harvest, then nothing. Plant small amounts every 2 weeks for a continuous supply.

Track Your Planting Schedule

The hardest part of spring planting isn’t the work — it’s remembering what to plant when. A planting calendar that knows your zone and calculates dates based on your actual last frost date takes the guesswork out.

garden.gg builds a personalized planting calendar for your zone, tracks what you’ve planted, and reminds you when it’s time to succession plant or transplant your indoor starts. Every planting becomes a data point that helps you grow better next season.