When to Plant Vegetables: A Frost-Date Guide for Every Growing Zone

"When should I plant tomatoes?" is the most Googled gardening question every spring, and the answer is always the same frustrating non-answer: it depends on where you live.

Which is true. But it shouldn't require a horticultural degree to figure out. Planting timing comes down to two numbers: your last spring frost date and your first autumn frost date. Everything else flows from those.

Understanding Frost Dates

Your last spring frost date is the average date after which there's only a 50% chance of frost in your area. Your first autumn frost date is the average date when frost becomes likely again. The gap between them is your growing season.

These dates are averages, not guarantees. In any given year, your actual last frost might be two weeks earlier or later than the average. That's why experienced growers talk about planting windows, not planting dates.

You can find your frost dates through your national meteorological service or agricultural extension office. In the US, the NOAA and local cooperative extension services provide historical frost data by location. In Canada, check Environment Canada's climate normals. In the UK, the Met Office provides similar data.

The Timing Framework

Once you know your last frost date, every vegetable falls into one of four categories:

Cold-Hardy Crops (Plant 4-6 weeks before last frost)

These tolerate frost and even light freezes. Get them in the ground early:

Peas, broad beans, spinach, kale, lettuce, radishes, turnips, onion sets, garlic (autumn-planted), Swiss chard, pak choi, rocket/arugula.

Direct sow these as soon as the soil is workable, often while there's still frost at night. They actually perform better in cool conditions and tend to bolt (go to seed) in summer heat. Many of these cold-hardy crops also make excellent understory plants in a seven-layer food forest.

Semi-Hardy Crops (Plant 2-3 weeks before last frost)

These tolerate light frost but not hard freezes:

Beets, carrots, potatoes, parsnips, kohlrabi, broccoli transplants, cabbage transplants, cauliflower transplants.

For transplanted crops (broccoli, cabbage, cauliflower), start seeds indoors 6-8 weeks before your planned transplant date. For direct-sown root crops (carrots, beets, parsnips), sow when soil temperature reaches about 7-10°C / 45-50°F.

Tender Crops (Plant at or after last frost date)

These are killed by frost. Wait until the danger has passed:

Tomatoes, peppers, aubergine/eggplant, beans (bush and pole), sweetcorn, cucumbers, courgette/zucchini, summer squash.

For tomatoes and peppers, start seeds indoors 6-8 weeks before your last frost date and transplant out after the last frost, ideally when night temperatures are consistently above 10°C / 50°F. For beans, sweetcorn, and cucumbers, direct sow after last frost when soil is warm (at least 15°C / 60°F).

Heat-Loving Crops (Plant 2-4 weeks after last frost)

These need warm soil and warm nights to thrive:

Winter squash, pumpkins, melons, watermelons, okra, sweet potatoes.

Don't rush these. Planting in cold soil leads to poor germination and stunted growth. Wait until soil temperature is at least 18°C / 65°F. In shorter-season climates (Zones 3-5), start squash and melons indoors 3-4 weeks before transplanting out.

Indoor Seed Starting: The Timeline

Counting backwards from your last frost date:

10-12 weeks before: Peppers, aubergine. These are slow to germinate and grow, so they need the longest head start.

8-10 weeks before: Tomatoes. Don't start them too early. Leggy, root-bound transplants perform worse than stocky younger ones.

6-8 weeks before: Brassicas (broccoli, cabbage, cauliflower, Brussels sprouts) if transplanting out 2-3 weeks before last frost.

4-6 weeks before: Lettuce and leafy greens for early transplants. Herbs like basil (start later; basil is very frost-sensitive).

3-4 weeks before: Squash, melons, cucumbers if starting indoors. Don't start these too early. They don't transplant well with large root systems, so you want small, vigorous transplants.

Succession Planting: Extend Your Harvests

Planting everything at once gives you a glut followed by nothing. Succession planting spreads your harvest across the season:

Lettuce and salad greens: Sow a short row every 2-3 weeks from early spring through autumn. Stop during the hottest weeks of summer (they'll bolt), then resume in late summer for autumn harvests.

Beans: Make 2-3 sowings, 3 weeks apart, starting from last frost. This gives you fresh beans for 2-3 months instead of 3 weeks.

Radishes and turnips: Sow every 2 weeks. They mature in 25-35 days, so frequent small sowings beat one large one.

Sweetcorn: Plant in blocks (not rows), with 2-3 successive plantings 2 weeks apart for an extended harvest.

Succession planting pairs well with the guild approach. See how to design a fruit tree guild for combining annual and perennial timing in a food forest system. Understanding which plants support each other helps you choose what to rotate into each succession slot.

Autumn and Winter Planting

Most gardeners think the season ends with the first frost, but there's a whole second planting window:

Late summer (8-10 weeks before first frost): Plant brassicas, kale, spinach, and lettuce for autumn harvest. Many of these are actually sweeter after frost exposure, which converts starches to sugars.

Autumn: Plant garlic (4-6 weeks before ground freeze), broad beans (in mild winter areas), and overwintering onion sets.

Late autumn: Sow cover crops (crimson clover, winter rye, hairy vetch) to protect and build soil over winter. This is one of the highest-value things you can do for next year's garden.

Microclimates Change Everything

Your frost dates are an average for your area, but your garden has microclimates that modify those dates:

South-facing walls absorb heat and create warm pockets where you can plant tender crops 1-2 weeks earlier. Low-lying areas collect cold air and may frost later in spring and earlier in autumn than the rest of your garden. Raised beds warm faster in spring than in-ground beds. Urban gardens are often a full zone warmer than surrounding rural areas due to the heat island effect.

Pay attention to your specific site. After a couple of seasons of observation, you'll know which spots are your warm pockets and which are your frost traps. Mapping these microclimates is part of permaculture zone planning, placing the right crops in the right zones based on how you actually move through your property.

Build Your Own Calendar

Generic planting charts are starting points, but the best calendar is one built from your actual frost dates, soil conditions, and observed microclimates.

This is one of the things I designed PatternBase to handle well. The planting calendar generates timing recommendations based on your specific frost dates and hardiness zone, with weather integration that fires frost warnings when your plants are at risk. It tracks what you planted when, so over time you're building a documented record of what timing works for your conditions, not following a generic chart from a different climate.

Whether you use an app or a wall calendar, the principle is the same: know your frost dates, group your crops by cold tolerance, and let the soil temperature guide your timing. You can look up frost tolerance, days to maturity, and planting windows for 2,000+ species in the PatternBase plant guide.

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PatternBase is a free permaculture garden design tool launching March 2026. Create your free account to start documenting what actually grows.