Video Overview
Wondering about companion planting with onions? Find out who belongs in Mr. Onion's neighborhood! Whether you're planting onions from organic seed, as sets (bulbs), or transplants, the rules of onion companion planting are the same.
Onions Are in the Allium Family
Companion planting goes by vegetable family, which makes it easier to understand. Onions are in the allium family along with their smelly cousins: leeks, chives, and garlic.
Plants function as good or bad neighbors to each other for a couple of reasons:
- Physically: Plants get along if their roots spread at different depths in the soil—they literally will not crowd each other.
- Biologically: Plants can work in harmony as "trap crops" that attract insects away from other vegetables, or a plant's aroma may be offensive to some pests.
- Chemically: Plants can alter the composition of soil, as when peas fix nitrogen from the air into soil.
Onions as Physical Companion Plants
Lettuce, carrots, and onions grow roots that go down to different depths—and these vegetables can grow comfortably side by side.
Onions as Biological Companion Plants
Onions can repel many insects and are often grown as companion plants. According to Cornell University, onions are beneficial when planted with:
- Brassicas: Broccoli, Brussels Sprouts, Cauliflower, Cabbage, Kale, Collards, Radishes, Turnips.
- Others: Beets, Chard, Lettuce, Peppers, Strawberries, Tomatoes.
The Don'ts
Some onion combinations are destructive. Onions will stunt the growth of peas and beans.
Plant Your Own Onions
Now that you know where to plant onions, learn which onions will do best in your climate. Check out our growing guide and video about growing onions.