Fall in Zone 4 is a short, busy season with two jobs: harvest everything the summer grew, and sow the hardy crops that will carry the garden into the cold. The average first frost arrives September 15–October 1, which leaves a few good weeks after summer ends — enough for a final round of lettuce, spinach, radishes and peas, and for planting garlic and spring bulbs. This guide covers the Zone 4 fall in full: what to harvest and when, what to sow, how to protect crops from early frosts, and how to put beds to bed properly. Winter lows reach -30 to -20°F, so the garden needs to be closed down deliberately, not abandoned.
Zone 4 in fall: the frost window
Zone 4 is a very cold northern USDA zone, with winter lows of -30 to -20°F. The average last spring frost falls May 1–15 and the average first autumn frost falls September 15–October 1, which leaves roughly twenty weeks between the two on average. Those dates are USDA zone averages from the USDA Plant Hardiness Zone Map and NOAA frost records — they are ranges, not exact dates for any one garden, and they vary by microclimate, elevation and year, so check your local extension service before you make any decision that depends on frost. Use the frost date calculator to confirm the averages for your zone, and the hardiness zone finder if you are not sure of your zone. The planting calendar hub lists every zone and month, and the guides hub gathers all of our seasonal guides in one place.
What to sow, plant and transplant in fall
Fall sowing in Zone 4 is short but real. In early fall, direct-sow fast hardy crops that mature before the first frost, September 15–October 1: radishes (25–40 days), lettuce (45–60 days), spinach (40–50 days) and peas (60–70 days) if sown early enough. Kale, chard, carrots (60–80 days) and beets (50–70 days) sown in late summer keep growing into fall and sweeten after a light frost. Transplant fall brassicas — broccoli, cabbage, cauliflower and Brussels sprouts — started indoors in summer, so they are well grown before the cold arrives.
The most important fall planting is garlic, set into well-drained soil a few weeks before the ground freezes and mulched thickly, plus spring bulbs for next year. Sow a cover crop such as winter rye or clover on empty beds to protect the soil over winter, and sow herbs and microgreens indoors for the kitchen.
For crop-by-crop detail, see our planting pages for garlic in Zone 4, kale in Zone 4, carrots in Zone 4, broccoli in Zone 4 and lettuce in Zone 4, and the growing guides for growing garlic, growing kale and growing broccoli.
What to harvest in fall
Fall is the harvest season for storage crops in Zone 4: potatoes (70–120 days), carrots (60–80 days), beets (50–70 days), onions and winter squash, all dug or picked before the first frost, September 15–October 1, or soon after it. Kale, chard, Brussels sprouts and leeks sweeten after a light frost and can be left in the ground under mulch for a while. Pick the last tomatoes, peppers and beans before frost, ripening green tomatoes indoors. Apples, pears and other fruit are picked as they ripen, and herbs are cut and dried or frozen before the cold finishes them.
Frost protection in fall
Fall protection in Zone 4 is about stretching the season, not stopping winter. The average first frost arrives September 15–October 1, and a light frost only damages tender crops — hardy crops such as kale, chard, carrots, beets, leeks and Brussels sprouts tolerate it and often taste better afterwards. Row cover or fleece over lettuce, spinach and peas adds a week or two of harvest, and a cold frame or polytunnel adds more. Cover crops before sunset so the cover traps the day's warmth, weigh the edges down, and ventilate cold frames on sunny days so plants do not overheat. Mulch root crops thickly so the ground stays workable and you can keep digging after the first frosts. Bring tender potted plants indoors before the first frost, and drain hoses and outdoor taps before the first hard freeze. Wind and heavy rain can flatten tall fall crops, so stake Brussels sprouts and tall kale, and clear fallen leaves from beds so they do not smother low crops.
Watering in fall
Fall watering in Zone 4 is lighter than summer, but it still matters. Cool-season crops need steady moisture to grow well, and newly planted garlic, bulbs, perennials and shrubs need water to establish roots before the ground freezes. Water in the morning, deeply and less often, and stop watering once the ground is frozen. Reduce watering as temperatures fall and days shorten — overwatering in cold soil causes rot, especially in containers and heavy soils. Mulch helps hold autumn moisture, but keep mulch a little away from stems so it does not trap damp against them. Give evergreens and newly planted trees a deep watering before the ground freezes, because they lose moisture through winter even when dormant. Drain hoses and irrigation lines before the first hard freeze so they do not split.
Pests and diseases to watch in fall
Fall pests in Zone 4 are fewer but still active. Slugs and snails thrive in damp autumn weather and eat lettuce, spinach and young brassicas — keep checking and removing them, and clear fallen leaves where they hide. Aphids cluster on late brassicas and hardy greens; wash them off or leave them for the cold to finish. Cabbage white caterpillars may still be feeding on brassicas in early fall. Clubroot and other soil diseases build up where brassicas are grown in the same bed year after year, so rotate crops and do not plant brassicas where they grew last year. Clear away diseased foliage rather than composting it, so spores do not overwinter in the heap. Mice and voles move into gardens in fall looking for stored food and shelter — protect stored crops, clear debris, and do not mulch too early, before the ground freezes, or you give them a warm home.
Month by month: fall in Zone 4
September
In September, harvest summer crops and sow the fall garden: radishes, lettuce, spinach and peas sown early in the month still mature before the first frost, {d['first']}. Dig potatoes and pick winter squash, and transplant fall brassicas started indoors in summer.
October
In October, plant garlic and spring bulbs, mulch beds and perennials, and sow a cover crop on empty beds. Harvest kale, chard and Brussels sprouts, which sweeten after a light frost, and protect lettuce and spinach with row cover.
November
In November, finish putting the garden to bed: clear spent plants, compost healthy foliage, drain hoses and irrigation, store tools, and check stored crops. Order seed early for spring, when the average last frost falls {d['last']}.
Frequently asked questions
What can I still sow in fall in Zone 4?
Fast hardy crops sown early in fall — radishes (25–40 days), lettuce (45–60 days) and spinach (40–50 days) — can still mature before the first frost, September 15–October 1. Garlic is the main fall planting in every zone: cloves go in a few weeks before the ground freezes. In the coldest zones, outdoor sowing after early fall is not realistic.
When is the first frost in Zone 4?
On average, September 15–October 1. That is a zone average from USDA and NOAA records, not an exact date for your garden — it varies by microclimate, elevation and year, so check your local extension service and watch the forecast from late summer onwards.
Which crops survive a fall frost?
Kale, chard, carrots, beets, leeks, Brussels sprouts and parsnips tolerate light frosts and often taste sweeter afterwards. Lettuce, spinach and peas survive a light frost with row cover. Tender crops — tomatoes, peppers, cucumbers, beans, zucchini and basil — do not survive frost at all.
Should I plant garlic in fall?
Yes. Garlic planted in fall establishes roots before winter and produces a far better harvest than spring-planted garlic. Plant cloves a few weeks before the ground freezes, in well-drained soil, and mulch thickly. It overwinters under snow or mulch and grows away in spring.
What should I do with empty beds in fall?
Improve them. Fork in compost, sow a cover crop on beds that will stand empty over winter, and mulch bare soil so winter rain does not wash it away. Fall is the best time to build soil for next year, because the ground is still warm enough for soil life to work.
Planning the rest of your year
Each season in Zone 4 connects to the next: spring sowing decides the summer harvest, summer succession sowing decides the fall garden, fall planting decides next spring, and winter planning decides all of it. Read the companion guides for this zone — Spring in Zone 4, Summer in Zone 4, Winter in Zone 4 — and use the planting calendar, the frost date calculator, the hardiness zone finder and the seed-starting calculator to plan around your own frost dates. All frost dates in this guide are zone averages from the USDA Plant Hardiness Zone Map and NOAA records — they vary by microclimate, elevation and year, so check your local extension service before you plant tender crops outside. The guides hub and the tools hub gather everything else you need for the year.