Gardening in a short-season climate means every week counts. For those of us with a last frost date in May, it’s essential to start seeds at the right time to make the most of the growing season. This guide walks you through what to start indoors, what to direct sow, when to harden off seedlings, and how to prep your garden and protect it from those surprise spring frosts.
1. Understanding Your Frost Dates
Before you plant anything, you need to know your last frost date. This is the average last day in spring when frost is expected—around early to mid-May for many northern gardeners. Use local gardening resources, almanacs, or weather-tracking apps to confirm yours.
Planning around this date helps you time seed starting, transplanting, and direct sowing just right.
2. Seed Starting Indoors: A Month-by-Month Timeline
Indoor seed starting gives your plants a head start, especially in cooler climates. Here’s a general guide based on a May frost date:
- 12–14 Weeks Before Last Frost (Late Jan–Early Feb):
- Onions, leeks, celery
- 8–10 Weeks Before Last Frost (Early–Mid March):
- Peppers, eggplant
- Herbs: parsley, thyme, oregano
- 6–8 Weeks Before Last Frost (Late March–Early April):
- Tomatoes, cabbage, broccoli, kale
- Herbs: sage, chives
- 4–6 Weeks Before Last Frost (Mid–Late April):
- Basil, summer savory, marjoram
- Dill (optional – can also be direct sown)
Give seedlings good light, warmth, and airflow to prevent damping off. Herbs can often be started in small trays and moved to their own pots once established.
3. When and How to Harden Off Seedlings
Hardening off is the process of gradually exposing your indoor seedlings to the outdoors to toughen them up.
Begin about 7–10 days before your planned transplanting date (usually around mid-May):
- Day 1–2: Place seedlings outside for 1–2 hours in a sheltered spot
- Gradually increase time and exposure to sun and wind over the next week
- Bring them in at night if it’s still cold
Watch tender herbs like basil—they’re especially sensitive to cold nights and wind.
4. Direct Sowing: What to Plant and When
Some plants prefer to be sown directly into the ground. Here’s a guide:
- Early Spring (Late April–Early May):
- Peas, spinach, carrots, beets, radishes, lettuce
- Herbs: cilantro, dill, chamomile
- After the Last Frost (Mid–Late May):
- Beans, corn, cucumbers, squash, melons
- Herbs: basil (if not started indoors), borage, nasturtiums
Tip: Succession sow quick-maturing herbs like cilantro and dill every 2–3 weeks for a continuous harvest.
5. Preparing Your Garden Beds for a Strong Start
Well-prepared soil sets the foundation for a healthy garden:
- Test and amend soil early in the season
- Add compost or aged manure
- Mulch beds to retain moisture and block weeds
- Remove early weeds while they’re small
- Consider raised or permanent beds for better drainage and early planting
6. Frost Protection Strategies for Surprise Spring Cold Snaps
Late spring frosts can surprise even experienced gardeners. Be ready with:
- Row covers, frost blankets, or old bedsheets
- DIY cold frames from windows or clear bins
- Cloches (even cut plastic bottles work!)
- Companion planting to provide natural protection (e.g., leafy greens sheltering basil)
Check the weather daily during transplanting season and cover plants at night if temperatures dip.
Conclusion
Gardening with a last frost in May means a bit more planning—but it’s worth every seed. Start indoors strategically, sow directly when the soil is ready, and give your seedlings the best chance with soil prep and frost protection.
Don’t forget to enjoy the process—and share what you’re planting this year in the comments!
Bonus: Download our free Seed Starting & Herb Growing Cheat Sheet (coming SOON) to stay on track all season long!
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