December in Zone 3 is the garden's rest month. The ground is frozen or snow-covered, the average last frost (May 15 to June 1) is months away, and the real work is indoors: planning, ordering seeds, and growing microgreens and herbs on a windowsill. A quiet December is not a wasted December — gardeners who plan now rarely feel rushed in spring. This guide covers what to plant in december zone 3.
What December means in Zone 3
USDA Zone 3 has average winter lows of -40 to -30°F. The two dates that shape every decision are the frost averages: the average last spring frost falls around May 15 to June 1 and the average first autumn frost around September 1 to 15, giving a growing season of roughly 90 to 110 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 hardiness zone finder turns the averages into dates for your garden.
December garden task list
- Plan next year's garden on paper, including rotations and new crops to try.
- Order seeds early, while the full range is available.
- Clean and sharpen tools; oil wooden handles and hinges.
- Check stored produce and remove anything soft or sprouting.
- Feed garden birds and keep a dish of unfrozen water out.
- Repair cold frames, cloches and trellises before spring.
What to start indoors in December
Windowsill growing is the garden now: microgreens, herbs and a pot of lettuce keep things green. Onions and leeks are still a few weeks away for most gardeners — starting them too early gives weak, leggy plants. Use the month to plan and prepare: sort seeds, repair tools, and build or repair a cold frame. A few hardy flower seeds can be started indoors at the very end of the month if you have strong light. Use frost date calculator to work back from your last frost average, and give seedlings strong light and moist, well-drained soil.
What to direct-sow in December
Nothing is direct-sown outdoors this month. The ground is frozen or snow-covered, and seed sown now would rot or be eaten. Garlic planted in autumn is dormant under its mulch — leave it alone. The only outdoor sowing worth mentioning is none at all; the garden's work this month is planning, not planting. Sow into soil that crumbles in the hand, water gently, and mark every row.
What to harvest in December
There is no outdoor harvest to speak of, apart from the hardiest leeks or kale dug from under snow on a mild day — a rare bonus, not a plan. Stored onions, garlic, potatoes and squash are the pantry harvest, so check them weekly. Indoors, microgreens are ready in one to two weeks, and potted herbs supply the kitchen through the darkest weeks. Pick in the morning when leaves are crisp, and pick little and often so plants keep producing.
Frost protection in December
Frost and snow are the season now, not a threat to manage day by day. Keep mulch on garlic and perennials, keep pots insulated or sheltered, and do not disturb frozen plants — frozen foliage is brittle and breaks easily. The frost dates that matter are the spring ones, months away; use this quiet time to learn your zone's averages and check your local extension service for local guidance. Keep fleece, cloches and row cover within reach all month — a cover put on before dusk is the cheapest frost protection there is.
December 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 |
|---|---|---|---|---|---|
| Garlic | Direct sow (cloves) | 180–240 | 7–14 | Hardy | 6 in |
| Spinach | Direct sow | 40–50 | 7–14 | Hardy | 4–6 in |
| Radishes | Direct sow | 25–40 | 4–7 | Hardy | 2–3 in |
| Kale | Direct sow / transplant | 50–65 | 7–10 | Hardy | 12–18 in |
| Turnips | Direct sow | 40–60 | 7–10 | Hardy | 4–6 in |
| Carrots | Direct sow | 60–80 | 14–21 | Hardy | 2–3 in |
What not to do in December
Do not start tender seeds indoors yet — tomatoes sown now become leggy long before they can go out. Do not walk on frozen soil or frozen lawns; it damages structure. Do not overwater houseplants in the short, dark days. And do not order seeds without a plan: a drawer full of packets you will never sow is the most common winter gardening expense.
Looking ahead
For the full year, browse the planting calendar hub for every Zone 3 month.
Frequently asked questions
Can I plant anything outside in December in Zone 3?
Hardy crops such as peas, spinach, lettuce, radishes and carrots can go out in December 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 15 to June 1. Check your local extension service before planting.
When is the last frost in Zone 3?
The average last spring frost in Zone 3 falls around May 15 to June 1, and the average first autumn frost around September 1 to 15. 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 December in Zone 3?
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.
Should I plant garlic in December in Zone 3?
Garlic is an autumn planting in Zone 3: it needs 180 to 240 days and a cold period to form bulbs, so cloves go in before the ground freezes, spaced about 6 inches apart, and mulched thickly. If the ground is already frozen solid in December, the window has passed — plant garlic earlier next year rather than forcing cloves into frozen soil.