Potatoes, onions, and garlic are the backbone of a well-stocked kitchen, and they all share the same basic storage logic: cool, dark, and dry. But the specifics differ enough that treating them identically leads to premature sprouting, rot, and wasted food. A few targeted adjustments can extend the useful life of each by weeks.
Potatoes need darkness more than anything else
Light is the primary enemy of stored potatoes. Exposure to light — even indirect ambient light — triggers the production of solanine, a mildly toxic compound that turns potato skin green. Green-skinned potatoes are not automatically unsafe in small amounts, but the taste is bitter and the green areas should be cut away before eating.
Ideal storage conditions for potatoes:
- Temperature: 45 to 50°F (7 to 10°C) — cooler than room temperature, but not refrigerator cold
- Humidity: moderate (85 to 90%) — very dry air shrivels them
- Light: none
- Airflow: some ventilation prevents condensation
A basement, root cellar, or dark lower cabinet away from the stove and oven works well. Avoid the refrigerator — cold temperatures convert potato starches to sugars, making them sweet in flavour and causing them to brown more quickly when cooked. The USDA recommends storing potatoes at 45 to 50°F for longest shelf life.
Store in breathable containers: mesh bags, paper bags, cardboard boxes, or wooden crates. Plastic bags trap moisture and accelerate rot.
What to do with no basement or cool space
If you live in a warm climate or lack a cool storage area, potatoes will not keep as long — that is simply the reality. Buy smaller quantities more frequently, and store them in the coolest, darkest cabinet available, away from appliances that generate heat. Expected shelf life at room temperature (65 to 70°F) is about 1 to 2 weeks for most varieties.
Onions want dry air and airflow above all else
Onions are more tolerant of warmer temperatures than potatoes, but they are extremely sensitive to moisture. Dampness causes the outer skins to soften and rot sets in quickly, starting at the neck.
Ideal storage conditions for onions:
- Temperature: 40 to 50°F (4 to 10°C), but they tolerate up to 65°F reasonably well
- Humidity: low — below 70% relative humidity
- Light: minimal (less critical than for potatoes, but still a factor)
- Airflow: good ventilation is essential
The classic hanging mesh bag or open-weave basket is ideal because it allows air to circulate around every onion. A single layer in a shallow box also works. Do not store onions in plastic bags or sealed containers — they trap moisture and cut shelf life significantly.
Keep onions away from potatoes. As mentioned above, onions emit ethylene gas that triggers potato sprouting, and potato moisture accelerates onion mould. They need separate locations.
How long do onions last?
| Variety | Properly stored shelf life |
|---|---|
| Yellow/brown onions | 2 to 3 months |
| Red onions | 1 to 2 months |
| White onions | 1 to 2 months |
| Sweet onions (Vidalia, Walla Walla) | 2 to 4 weeks |
| Green onions (scallions) | 1 to 2 weeks in fridge |
Sweet onions have higher water content and do not keep as long as storage varieties. If you buy sweet onions in bulk, use them first.
Garlic is the most forgiving of the three
Whole, unpeeled heads of garlic store well at room temperature in a cool, dry spot with good airflow. A small mesh bag, ceramic garlic keeper (unglazed, with ventilation holes), or simply a corner of a pantry shelf all work fine.
What garlic does not tolerate:
- Refrigerator humidity — promotes mould and premature sprouting in whole heads
- Plastic bags — traps moisture, same problem
- Direct sunlight or heat near a stove
A well-cured, fresh-from-the-farm head of garlic stored properly can last 3 to 6 months. Grocery store garlic often has a shorter window because it has already been in storage or transit for some time. Many growers on CollectiveCrop sell cured garlic and storage onions directly in fall — prime timing to stock up before winter.
Once you break the head
Once you pull cloves off a head, the clock speeds up.
- Unpeeled loose cloves: keep in a cool, dry spot, use within 10 days
- Peeled cloves: refrigerate in an airtight container, use within 1 week
- Minced garlic: refrigerate, use within 3 to 4 days
Garlic submerged in oil at room temperature is a botulism risk — the low-acid, anaerobic environment is exactly where that bacterium thrives. If you want garlic-infused oil, make it fresh as needed or refrigerate it and use within a few days (Health Canada and the FDA both advise against room-temperature storage).
The keep-them-separate rule in practice
To summarise the core rule: store each of these three in its own area, in a breathable container, with no plastic.
| Vegetable | Best location | Container | Refrigerate? |
|---|---|---|---|
| Potatoes | Dark basement, dark cabinet | Paper bag, mesh bag, cardboard box | No |
| Onions | Ventilated pantry or shelf | Mesh bag, open basket | No (whole) |
| Garlic | Cool, dry shelf | Mesh bag, ceramic keeper | No (whole head) |
Potatoes and onions should be at least a few feet apart — across the room is better. Garlic can coexist near onions since both prefer similar dry conditions and garlic does not emit significant ethylene.
What to do when they start to turn
Potatoes with small sprouts: cut the sprout off and a bit of the surrounding flesh, and use the potato promptly. Once extensively sprouted or green, compost them.
Onions starting to soften: peel, dice, and freeze immediately. Frozen diced onion keeps 6 to 8 months and goes directly from freezer to pan — no need to thaw.
Garlic with soft or mouldy cloves: discard affected cloves, use the firm ones right away. A single bad clove does not mean the whole head is lost.