Grow spinach, kale, mâche, claytonia, leeks, parsnips and carrots for winter harvest, sown late enough to avoid bolting and early enough to reach near-maturity before short days halt growth, and mulch roots heavily so the ground does not freeze solid. Cold tolerance varies by variety and by how gradually the cold arrives, so test the crop and the cover on your own site before relying on it. Do not pick leaves while they are frozen solid; harvest after they thaw.
Cold-hardy greens and roots are vegetables that tolerate frost and freezing weather and can be left in the garden through winter and picked as needed.
Hardy Crops Wait In The Garden Until They Are Needed
The carrier guide (Four-Season Growing & Season Extension) lists the following as surviving to 10°F (-12°C) unprotected: kale (it names ‘Winterbor’ and ‘Red Russian’), spinach, mâche, claytonia, leeks, parsnips, carrots under heavy mulch, Brussels sprouts and collards. The survival temperature is the carrier’s, with no source; take it as a rough guide and try the crop yourself.
How Cold Hardiness Works
Plants exposed to gradually falling temperatures adapt: they raise sugar levels in their cells, which lowers the freezing point of cell contents and protects against damage. Parsnips and kale taste sweeter after frost for this reason. A sudden hard freeze before a plant has adapted is more damaging than the same temperature after a cool spell. Wind and wet foliage worsen damage; cover and mulch lessen it.
What You Need
- Seed of hardy varieties.
- Mulch: straw, leaves or cut brush for roots.
- A cover — a cold frame or low tunnel for leaves (Cold Frames & Low Tunnels).
Method
Step 1: Sow in late summer. The carrier names August as the critical sowing month; the exact date depends on your climate and the crop’s days to maturity.
Step 2: Thin and keep weeded so plants are not stunted before winter.
Step 3: Mulch roots heavily before the ground freezes. Carrots and parsnips can stay in the ground if the mulch keeps the soil workable enough to dig.
Step 4: Cover leaf crops with a frame or tunnel to keep rain, wind and the worst of the cold off them.
Step 5: Harvest on mild days, after the leaves have thawed. Leaves handled while frozen bruise and blacken.
Step 6: Dig roots before the ground becomes unworkable or the mulch becomes a home for voles; check for rodents under the mulch.
Step 7: Harvest everything before spring regrowth if you do not want the plants to bolt and turn bitter. Some plants resume growth and flower; see Overwintering Biennials.
Common Mistakes
- Sowing too late — small plants cannot grow in short days.
- Leaving roots uncovered — frozen ground cannot be dug.
- Letting mulch harbour voles — they eat the roots.
What’s Next
- Learn next: Harvest-Only Winter Crops — planning how much to sow
- Combine with: Root Crop Role — the role of roots in the diet