April in Zone 4 is the busiest sowing month of the year. The average last frost (May 1 to 15) falls in this window, so the month splits in two: hardy crops early, tender crops once frost has passed. The growing season here runs roughly 120 to 140 days, so a well-timed April sets up the whole summer. This guide covers what to plant in april zone 4: indoor sowings, direct sowings, harvests, and frost care at the turning point of the year.
What April means in Zone 4
USDA Zone 4 has average winter lows of -30 to -20°F. The two dates that shape every decision are the frost averages: the average last spring frost falls around May 1 to 15 and the average first autumn frost around September 15 to October 1, giving a growing season of roughly 120 to 140 days. Those figures come from USDA zone averages and NOAA frost records — they are averages, not promises for any single garden, and they vary with microclimate, elevation and the year itself. Always check your local extension service before planting tender crops outside. The planting calendar hub gathers every month, and planting calendar by ZIP turns the averages into dates for your garden.
April garden task list
- Transplant hardened-off brassicas — broccoli, cabbage, cauliflower and kale — into prepared beds.
- Direct-sow hardy crops in succession, a little every two weeks.
- Mulch beds once the soil has warmed, to hold moisture and suppress weeds.
- Set out supports for peas and the first bean poles.
- Water newly sown beds gently and keep seed beds damp until germination.
- Begin a regular slug patrol and check brassicas for cabbage white eggs.
What to start indoors in April
Indoor sowing narrows to the heat-lovers now. Cucumbers, zucchini and squash are started indoors only if you want the earliest possible plants; most gardeners direct-sow them once the soil warms. Basil, peppers and eggplant started earlier are potted on and hardened off in the final days of the month. Succession sowings of lettuce and herbs indoors keep a steady supply coming, and flowers such as marigolds — good companions for tomatoes — can be started now. Use seed-starting calculator to work back from your last frost average, and give seedlings strong light and moist, well-drained soil.
What to direct-sow in April
Direct sowing is wide open for hardy and half-hardy crops. Peas, spinach, lettuce, radishes, carrots, beets and turnips all go in, and a second sowing of radishes and lettuce two weeks after the first keeps the harvest continuous. Potatoes go in in earnest. Sweet corn can be sown at the end of the month in the warmest spots, though most gardeners wait until the soil is reliably warm. Beans wait until frost has passed, so hold them a little longer. Sow into soil that crumbles in the hand, water gently, and mark every row.
What to harvest in April
Harvests pick up: radishes sown under cover, early spinach and lettuce, overwintered herbs, and the first asparagus spears if you have an established bed — asparagus takes two to three years to establish, so an early cutting is a small reward for patience. Rhubarb is in full production now. Pick lettuce as cut-and-come-again leaves rather than whole heads to stretch the supply. Pick in the morning when leaves are crisp, and pick little and often so plants keep producing.
Frost protection in April
This is the month the frost calendar turns. Until the average last frost passes, tender plants stay protected or indoors; after it, they can go out — but watch the forecast for a late frost for at least two weeks beyond the average date. Keep fleece handy for every tender transplant for its first fortnight outside. If a frost is forecast after you have planted out, water the soil in the afternoon and cover plants before dusk; damp soil holds heat better than dry soil. Keep fleece, cloches and row cover within reach all month — a cover put on before dusk is the cheapest frost protection there is.
April planting data
The table below uses broad published ranges — they vary by variety, climate and soil.
| Crop | How to sow | Days to maturity | Germination (days) | Cold tolerance | Spacing |
|---|---|---|---|---|---|
| Tomatoes | Start indoors | 60–85 | 7–14 | Tender | 24–36 in |
| Bell peppers | Start indoors | 60–90 | 7–14 | Tender | 18–24 in |
| Lettuce | Direct sow / transplant | 45–60 | 7–10 | Hardy | 8–12 in |
| Carrots | Direct sow | 60–80 | 14–21 | Hardy | 2–3 in |
| Peas | Direct sow | 60–70 | 7–14 | Hardy | 2–3 in |
| Radishes | Direct sow | 25–40 | 4–7 | Hardy | 2–3 in |
What not to do in April
Do not plant beans, squash, cucumbers or basil outside before the frost averages have passed — they are tender and a single cold night kills them. Do not let seed beds dry out just as germination starts; a dry crust is the most common reason for patchy carrots and parsnips. And do not crowd transplants: broccoli and cabbage need 18 to 24 inches of spacing, and crowded plants stay small and disease-prone.
Looking ahead
Next month, May in Zone 4 picks up where this guide leaves off. For the full year, browse the planting calendar hub for every Zone 4 month.
Frequently asked questions
Can I plant anything outside in April in Zone 4?
Hardy crops such as peas, spinach, lettuce, radishes and carrots can go out in April when the soil can be worked, while tender crops such as tomatoes, beans, squash and basil must wait until after the average last frost, May 1 to 15. Check your local extension service before planting.
When is the last frost in Zone 4?
The average last spring frost in Zone 4 falls around May 1 to 15, and the average first autumn frost around September 15 to October 1. These are USDA/NOAA zone averages, not exact dates — microclimate and the year itself shift them, so check your local extension service.
What seeds should I start indoors in April in Zone 4?
Slow growers such as onions, leeks, celery, peppers and eggplant are started earliest, while tomatoes follow once you have strong light. Work back from your last frost average.
Is April too early or too late to start tomatoes in Zone 4?
Tomatoes take 60 to 85 days to mature and germinate in 7 to 14 days. In April, start them indoors only if the last frost is still several weeks away and you have strong light; sown too early they become leggy, and set out too early they stall in cold soil. Transplant only after the last frost has passed.