By Emily ParkerUpdated November 2026
Potato and onion companion planting can work well when both crops are given enough room and timed correctly. Growing them side by side may help keep some pests guessing, make better use of garden space, and reduce the amount of ground left bare between plantings. This guide covers how to set them up, what spacing to use, and where things go wrong.
Why Potatoes and Onions Share a Bed
The main benefit is pest confusion rather than any direct boost to growth. Onions give off a sulfur-based scent that some gardeners believe deters potato pests such as aphids and certain beetles. The evidence for this is mostly anecdotal, so treat it as a helpful bonus rather than a guarantee. The bigger practical gain is that onions are slim, upright plants that sit easily between potato rows and fill space that would otherwise go unused.
Shopping for one? See our guide: 6 Best Onions and Potatoes Companion Planting Books and Guides for 2026.
The two crops also have different root zones and harvest times. Potatoes form tubers in the upper 6 to 12 inches of soil, while onion bulbs sit near the surface, so they compete less for nutrients than two heavy feeders would.
Setting Up the Bed Step by Step
- Plant potatoes first. Set seed pieces 12 inches apart in rows spaced 30 to 36 inches apart, about 4 inches deep.
- Plant onion sets or transplants in the gaps between potato hills, about 4 inches apart, at a depth where the neck sits just above the soil line.
- Keep onions at least 6 inches from the nearest potato stem to reduce root competition.
- Hill the potatoes as they grow, but pull soil gently around the onions rather than mounding it over their bulbs.
- Water both crops evenly. Potatoes need about 1 to 2 inches of water per week, while onions prefer slightly drier conditions as bulbs mature.
Timing and Spacing Factors That Matter
Timing decides whether the pairing works. Onion sets and transplants can go in as soon as the soil can be worked in early spring, usually 4 to 6 weeks before your last frost date. Potatoes are typically planted a couple of weeks later, once soil temperatures reach about 45°F. Starting onions first gives them a head start before the potato canopy shades them.
Harvest timing matters too. Onions are usually ready when about half the tops have fallen over, often mid to late summer. Potatoes can be dug as new potatoes earlier or left to mature until the vines die back. Plan to pull onions first so the potato bed stays undisturbed for longer.
Common Mistakes to Avoid
- Planting onions too close to potato stems, which leads to stunted bulbs.
- Overwatering onions in the same bed, which can encourage rot.
- Mounding soil over onion bulbs during hilling, causing them to split or rot.
- Skipping crop rotation. Do not grow potatoes or onions in the same spot year after year.
- Expecting pest control alone. Check plants weekly for beetles, aphids and signs of blight.
Recommended Gear
A soil thermometer helps you confirm the 45°F threshold before planting potatoes, which keeps you from setting tubers into cold ground. View on Amazon
A long-handled hand cultivator makes it easier to loosen soil between onions without disturbing potato roots. View on Amazon
For more on pairings that work in mixed beds, see Companion Planting for Onion: 8 Best Pairings and What to Avoid and Companion Planting Onions and Garlic: A Step-by-Step Guide for Beginners. If you are planning a larger layout, Vegetable Garden Layout Companion Planting: A Step-by-Step Guide covers how to fit several crops together.
FAQ
Do potatoes and onions really repel pests from each other?
The evidence is limited and mostly based on gardener experience. Onion scent may confuse some pests, but it should not replace regular scouting and good sanitation.
How far apart should potatoes and onions be planted?
Keep onions at least 6 inches from potato stems and space rows 30 to 36 inches apart. This reduces root competition and leaves room to work the bed.
Can I plant potatoes and onions in containers together?
You can, but use a container at least 18 inches deep and wide for potatoes, and give onions their own section. Container soil dries out faster, so check moisture daily in hot weather.
Conclusion
Potato and onion companion planting works best when you start onions early, keep them spaced away from potato stems, and harvest them first. Use the setup steps and timing guidance above, and watch for pests and moisture problems through the season. With a little planning, both crops can share a bed without losing yield.
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About Emily Parker
Emily Parker is part of our editorial team and reviews and edits our vegetable & edible gardening guides, checking product details against manufacturer specifications and owner feedback.
