Root cellar basics: cool, steady, and a little damp.

A root cellar keeps carrots, potatoes, cabbage, and apples through the winter without power. It works because earth and stone hold a steady temperature, and a pair of vents lets moisture out before mold moves in. The rest is a weekly habit of checking what you've stored.

By Morgan Reid, author of The Lost Tools Handbook

Two gardeners tending rows of vegetables, one with a long-handled hoe and one pushing a wheel hoe, a barn behind them

The short answer

A root cellar is a cool, stable, humid space, usually underground or well insulated. Most roots keep best at 32 to 40°F (0 to 4°C), with 85 to 95% relative humidity for carrots and beets and slightly drier air for onions and winter squash. Build it on a shaded, well-drained site with two vents (one low for cold intake, one high for warm exhaust) and a tight door, and keep apples and pears apart from potatoes and leafy greens.

What goes where in the cellar?

Tap what you’re storing and you’ll get the temperature and humidity it wants, how to pack it, and what to keep it away from.

1 · What are you storing?

Tap everything you plan to keep down there.

2 · How is the air down there?

3 · Cellar temperature (optional)

Leave it blank if you don’t have a reading yet.

How a root cellar works

Unlike a refrigerator, a root cellar uses thermal mass, earth, stone, or packed insulation, to hold a steady temperature just above freezing, and controlled ventilation to manage humidity. The surrounding ground evens out day-to-night and seasonal swings. Simple low and high vents create a gentle airflow that lets excess moisture escape and prevents condensation and mold. Designed well, it needs no energy at all.

Good candidates include carrots, beets, turnips, potatoes, rutabagas, cabbage, and apples.

Build a simple one, step by step

Choose the site. Pick a shaded, well-drained spot with stable soil. A north-facing slope or a spot against a basement wall is ideal. Avoid low spots that flood, and check the local water table before you dig.
Excavate and form the space. Size the room to your expected harvest. Line the walls with stone, concrete block, or treated timber, and insulate the outside with packed earth or straw. Raise the floor slightly, or use shelving to keep produce off damp ground.
Add ventilation and access. Fit at least two vents, one low for cold intake and one high for warm exhaust, plus a tight-fitting door to limit drafts. Build shelving, bins, and boxes for sand or sawdust.
Finish and test. Add a thermometer and a hygrometer, seal gaps against pests, and watch the readings for several days to confirm they're stable before you stock it.

Target conditions

Crop	Temperature	Humidity
Most roots	32 to 40°F (0 to 4°C)	Humid
Carrots, beets	32 to 40°F	85 to 95% relative humidity
Onions, winter squash	Cellar temperature	Slightly drier

If the air is too dry, store roots in closed bins with damp sand or sawdust. If it's too damp, open up the ventilation to cut the risk of mold.

Storing produce

Single layers or shallow bins so air can move around everything.
Keep the ripeners apart. Apples and pears give off ethylene, which speeds ripening in sensitive vegetables like potatoes and leafy greens. Store them separately.
Pack roots in sand. Sand- or sawdust-lined boxes hold humidity around carrots and other roots.
Rotate and inspect weekly. Move the oldest items to the front, and look and smell for soft spots or off odors.
Remove anything rotting at once so it can't spread. If you're unsure whether a food is safe, throw it out.

Keep it clean and pest-free

Before each season, clean and dry the cellar: sweep and wash the shelves, check the walls for mold, and seal any cracks. Keep rodents out with physical barriers like screens and a secure door, use food-safe containers only, and never use chemical fumigants near food. Check the thermometer and hygrometer weekly along with the produce.

No room for a full cellar?

An insulated cooler or chest with ice packs can serve as a temporary cold space.
A refrigerator or a root bin inside one gives precise control for small quantities.
Burying insulated bins, or a buried pallet with a tarp, gives part of the cellar effect without heavy digging.
A small solar or battery fan on a cellar vent helps airflow during still periods.

The best way to start is small: one sand box of carrots and one crate of apples for a season, to learn the rotation and inspection routine before you build bigger.

A starter kit

A thermometer and a hygrometer
Sturdy shelving, shallow crates, and bins
Food-grade sand, sawdust, or peat for sand boxes
A weatherproof door or insulated hatch, vent pipes, and pest screens
Sealable containers and labels for rotation

Harvesting the crops to fill it? See how to use a scythe and sickle.

What you need to stock a root cellar

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What temperature should a root cellar be?

Most roots keep best at 32 to 40 degrees F (0 to 4 degrees C). Carrots and beets like 85 to 95 percent humidity, while onions and winter squash prefer slightly drier air.

Can you store apples with potatoes?

Keep them apart. Apples and pears give off ethylene, which speeds ripening in sensitive vegetables like potatoes and leafy greens, so store them in separate areas.