No, you should not store onions with potatoes. Onions release ethylene gas and moisture that cause potatoes to sprout and spoil faster, while potatoes’ own respiration can accelerate onion decay. Keep them separate for maximum shelf life.
Onions and potatoes have conflicting storage needs. Onions prefer cool, dry, dark, well-ventilated spaces (45-55°F), while potatoes need slightly cooler, darker, more humid conditions (38-50°F, 90% humidity). Stored together, ethylene from onions triggers potato sprouting, and moisture from potatoes can rot onions.
- Ethylene Effect: Onions emit ethylene gas, which accelerates sprouting in potatoes.
- Moisture Exchange: Potatoes release moisture, creating a humid environment that causes onions to rot.
- Temperature Needs: Onions store best at 45-55°F; potatoes at 38-50°F. Compromise harms both.
- Shelf Life Impact: Separate storage can keep onions 3-4 months and potatoes 2-3 months; together, they may last only weeks.
Why Onions and Potatoes Don’t Mix
Onions and potatoes are both root vegetables, but their storage chemistry is at odds. Onions produce ethylene gas, a natural plant hormone that promotes ripening and sprouting. Potatoes are highly sensitive to ethylene: even low levels can trigger early sprouting and green skin (due to solanine development, which is toxic). Additionally, potatoes have high moisture content and respire, releasing water vapor. Onions need dry air to prevent mold and rot; the humidity from potatoes creates ideal conditions for onion spoilage.
Temperature is another conflict. Onions thrive at 45-55°F (7-13°C) with low humidity (65-70%). Potatoes prefer 38-50°F (3-10°C) with high humidity (90%). A pantry at room temperature (60-70°F) is too warm for both, but storing them together in a cool basement might still cause issues due to ethylene and moisture. The result: potatoes sprout and soften, onions become mushy or moldy, and both lose flavor.
Best Storage Conditions for Onions
Store whole, uncut onions in a cool, dry, dark, well-ventilated place. Ideal temperature: 45-55°F. Avoid plastic bags; use mesh bags, wire baskets, or paper bags with holes. Keep away from potatoes, apples, and pears (which also emit ethylene). Do not refrigerate whole onions—the cold converts starches to sugars, making them soft and prone to mold. Once cut, wrap tightly and refrigerate for up to 7 days.
For long-term storage, choose cured onions with tight, dry skins. Store in a single layer or hung in mesh bags to allow air circulation. Check regularly and remove any that show signs of sprouting or rot to prevent spread.
Best Storage Conditions for Potatoes
Store potatoes in a cool, dark, humid, well-ventilated place. Ideal temperature: 38-50°F with 90% humidity. A root cellar or basement is perfect; a kitchen cupboard is too warm. Use a paper bag, burlap sack, or cardboard box with holes—avoid plastic, which traps moisture. Keep away from onions, apples, and bananas (ethylene producers). Do not refrigerate: starch converts to sugar, causing off flavors and discoloration when cooked.
Before storing, brush off dirt but do not wash (moisture invites rot). Inspect weekly and remove any sprouting or soft potatoes. For cut potatoes, submerge in water and refrigerate for up to 24 hours. Never store potatoes near heat sources or in direct light, which causes greening and solanine buildup.
Practical Storage Solutions for Small Kitchens
If space is tight, use separate containers or areas. Place onions in a mesh bag hung from a hook in a pantry, and potatoes in a paper bag on a lower shelf or in a cabinet away from the stove. You can also use a two-tier basket: onions on top (dryer air) and potatoes below (more humid). But keep at least a few inches apart.
Another option: designate a drawer for each. Onions can go in a ventilated wire basket on the counter (if cool and dark), while potatoes stay in a paper bag in a cupboard. Avoid storing them in the same drawer or bin. If you have a basement, use separate crates in different corners.
How to Tell If Onions or Potatoes Have Gone Bad
Onions: Look for soft spots, mold (especially at the neck), or a strong, unpleasant odor. Sprouting is okay if caught early—just remove the sprout and use quickly. Discard if more than half is soft or if there’s extensive mold.
Potatoes: Check for sprouting (remove sprouts and use soon), green skin (peel deeply to remove solanine, but discard if bitter), soft/wrinkled texture, or a musty smell. Potatoes stored with onions often sprout prematurely. If a potato is mushy or has dark rot, throw it away to avoid affecting others.
Pro Tips
- Store onions in mesh bags or nylon stockings with a knot between each onion to improve air circulation and prevent contact.
- Keep a small bowl of baking soda near stored potatoes to absorb excess ethylene and moisture—replace monthly.
- Use a wire basket with slotted sides for onions instead of solid bins to maximize airflow.
- If you must store both in a small space, place a layer of newspaper between them to buffer moisture and ethylene.
Common Mistakes to Avoid
- Storing potatoes in the refrigerator thinking it extends life—it converts starch to sugar, ruining texture and taste.
- Keeping onions in plastic bags, which trap moisture and cause rapid mold growth.
- Washing potatoes before storage—the added moisture promotes rot and shortens shelf life.
- Storing onions and potatoes together in a single bin or drawer, even if separated by a barrier, because ethylene gas still circulates.
FAQ
Can I store onions and potatoes in the same root cellar?
Yes, but keep them in separate bins or areas with at least a few feet of distance. Ensure good air circulation and avoid stacking them together. Monitor for sprouting and remove affected items promptly.
How long do onions and potatoes last when stored separately?
Properly stored onions can last 3-4 months, potatoes 2-3 months. Check weekly and remove any that show signs of spoilage.
What should I do if my potatoes have already sprouted from being stored with onions?
Remove all sprouts and green areas; the potato is still safe to eat if firm. Use immediately. For future, separate storage to prevent.
The Bottom Line
Storing onions with potatoes is a common mistake that shortens the life of both. By keeping them apart in cool, dark, well-ventilated spots, you’ll enjoy fresher produce for months. Remember: onions need dry air, potatoes need humidity, and ethylene is the enemy of spuds. A little separation goes a long way in reducing food waste and saving money.
