Root Cellar Too Warm or Too Dry?

A limp carrot is usually a dry cellar, not a warm one — and Alberta Agriculture publishes a number you can check yours against. Table 1 of Home Vegetable Storage (Agdex 732-15) gives a temperature and a relative humidity for every crop it covers. Most Canadian basements miss the humidity by a long way before they miss the temperature.

Sort which problem you have before you change anything. Water loss and rot both end with a soft vegetable, and they have opposite fixes.

Which one is it?

	Too dry (water loss)	Too warm	Rot
What you see	Limp, rubbery, bendy; shrivelled skin; the vegetable is smaller than it was	Sprouting; soft cabbage; produce going over faster than the published period	Soft and watery; foul smell; a white cottony mass or a grey-brown felt
What Alberta says is happening	”Vegetables are typically 80 to 90 per cent water. If the air surrounding the stored produce is dry, water will evapourate from the vegetables."	"Temperature has the greatest influence on the storability of vegetables. The ideal temperature will control respiration, disease and sprouting.”	A named storage disease
Where to go	This page, below	This page, below	Mould and rot in the root cellar

What Alberta publishes for each crop

This is Table 1 of Agdex 732-15, as printed. The temperature and humidity cells are shared down each storage group — the booklet prints a merged value once rather than repeating it on every row.

Storage group	Produce	Temperature (°C)	Relative humidity (%)	Storage period (months)
Cold and humid	Apples	0 – 1	90 – 95	varies up to 12 months; highly variety dependent
Cold and humid	Beets	0 – 1	95+	4 – 6
Cold and humid	Cabbages	0 – 1	95+	2 – 6
Cold and humid	Carrots	0 – 1	95+	4 – 6
Cold and humid	Parsnips	0 – 1	95+	2 – 5
Cold and humid	Radishes	0 – 1	95+	3 – 5
Cold and humid	Turnips	0 – 1	95+	4 – 6
Cool and humid	Potatoes – seed	4 – 5	not printed	not printed
Cool and humid	Potatoes – table	5 – 7	90 – 95	5 – 10
Cool and dry	Winter squash	10 – 12	70 – 75	4 – 6
Cool and dry	Marrow	10 – 12	70 – 75	4 – 6
Cool and dry	Pumpkins	10 – 12	70 – 75	2 – 4
Cold and dry	Onions – cured	0 – 3	70 – 75	4 – 8

Three things in that table are worth saying out loud, because they are where a home cellar usually goes wrong.

Onions are a cold crop, not a warm one. Alberta puts cured onions at 0 to 3 °C. It is the humidity that separates them from carrots, not the temperature — 70 to 75 per cent against 95 per cent or more.

Squash is the odd one out and cannot share the room. Alberta: “Squash cannot be stored with root crops because it requires a higher temperature and lower humidity.” Ten to twelve degrees against zero to one is not a compromise you can split.

Seed potatoes get a temperature and nothing else. Table 1 prints 4 to 5 °C for them and leaves the humidity and the storage period blank. We are not going to fill those in from the table potato row beside it.

Alberta’s own prose repeats three of these figures slightly differently, and we are not reconciling them for you. Their onion section says to store cured onions at 0 to 1 °C and 75 per cent R.H. where the table says 0 to 3 and 70 to 75. Their squash section says 75 per cent R.H. where the table says 70 to 75. Their compatibility section says potatoes store best at 5 to 8 °C where the table says 5 to 7. In every case the two figures overlap and neither is far from the other, so pick the table or pick the prose and you will be inside both.

If the room is too dry

This is the one that gets missed, because nothing looks wrong until the carrots bend. Alberta states the mechanism plainly:

“Vegetables are typically 80 to 90 per cent water. If the air surrounding the stored produce is dry, water will evapourate from the vegetables. High humidity is therefore desirable for most crops.”

And ventilation is what dries the room out, which is why cooling and humidifying have to be done together: “Since ventilation removes moisture, humidity should be added to the storage when ventilation is required.”

Their methods, all of them cheap:

• Wet the walls and floor before harvest, so the room starts damp rather than being dried out by the first crop you put in it.
• A tub of water with an old blanket draped into it, hanging so the blanket acts as a wick.
• A small household mister-type humidifier, which Alberta calls “an excellent way to provide humidity.”
• Perforated plastic bags for root crops, which “allows the vegetables to breathe while retaining moisture.” Alberta is specific that the perforations matter — an unperforated bag is a ventilation problem instead.
• Damp sand, which they call effective but more work.
• Plastic sheeting over the bins, which also reduces moisture loss.

One warning from their carrot section that costs nothing to follow: “Avoid storing vegetables in dark coloured plastic trash bags as these can give an objectionable taste to the vegetables.”

The one-room problem, answered by Alberta rather than by us

Most people have one cold room and several crops. Alberta publishes the compromise:

“Potatoes store best at a temperature of 5 to 8 C (41 - 46 F), while root crops store best at 1 C (34 F). The practical compromise is to keep the storage at 4 - 5 C (39 - 41 F) and the humidity high; root crops will keep almost as well and potatoes will not be harmed by too low a temperature.”

4 to 5 °C and high humidity is a published figure, not our average of two rows. It covers potatoes and root crops. It does not cover squash, pumpkin or marrow, which want 10 to 12 °C and a much drier room, and it does not cover onions, which want the cold but not the damp.

Sprouting, and what we will not tell you

Alberta names sprouting once, as one of three things the ideal temperature controls. They publish nothing about whether a sprouted potato or onion may be eaten, and no other Canadian authority we can reach publishes anything either. So this page does not answer that question. A sprouting crop is telling you the room is warmer than the table wants; that much is in the booklet, and the rest is not.

One thing about potatoes they do publish, and it is easy to confuse with sprouting:

“Potatoes not totally covered by soil in the garden or left in a room exposed to daylight or artificial room lights may develop a green colour. The potatoes should not be eaten if the tuber flesh is green as toxic chemicals are often found in association with green tubers.”

That is a statement about green flesh, not about sprouts, and it comes with its own fix: Alberta says to store potatoes in the dark, because “storage in the dark is necessary to prevent greening of the tuber skin.”

Potatoes that have gone sweet

A potato stored too cold is a quality problem with a published remedy rather than a loss. Alberta: “Potatoes stored at too cool a temperature will convert starch reserves to sugar. To improve the colour and flavour, remove tubers from storage seven to 10 days before use and store them in the dark at room temperature. This will ensure that the potatoes are not sweet when cooked or turn dark brown when fried.”

Before you blame the room

Alberta’s line on this is blunt and worth keeping in view: “It must be remembered that the quality of the produce will not be improved during storage but will decrease with time.” A cellar holds quality; it does not add any. If a crop went in bruised, wet or immature, no temperature will fix it — and their instruction for produce that went in damaged is to store it separately and eat it first.

For anything soft that is also watery, smells foul, or is carrying a visible fungus, stop here. That is a storage disease rather than a dry room, and it is covered on mould and rot in the root cellar, along with the one safety statement Alberta does publish. The broader setup — which rooms work, how to build or choose one, which crops to store at all — is on root cellaring in Canada.

As an Amazon Associate we earn from qualifying purchases. Some links on this site are affiliate links — they cost you nothing extra and help keep the site free. We do not test products; we report what Bernardin and Canadian health authorities publish. Affiliate disclosure.