Can Onions and Potatoes be Planted Together?
Companion planting involves growing different plants together to enhance growth, deter pests, and improve garden health. A common question is whether onions and potatoes can be planted together. The short answer is no—they should not be planted together.
In this post, we’ll explain why. We’ll cover nutrient competition, pest and disease risks, soil disturbance, and allelopathy.
Nutrient Competition
Onions and potatoes are both heavy feeders, meaning they require a lot of nutrients to grow well. When planted together, they compete for essential nutrients, like nitrogen, phosphorus, and potassium. This competition can lead to nutrient deficiencies, stunting the growth of both plants and reducing their yields.
For example, potatoes need ample nitrogen for leafy growth and tuber development. Onions also require nitrogen, but they need a good balance of phosphorus and potassium to develop healthy bulbs. Planting them together means they both fight for these nutrients, leading to poor growth and smaller harvests.
To avoid this issue, plant onions and potatoes separately and ensure each has access to the nutrients they need. Use soil tests to monitor nutrient levels and amend the soil accordingly to support healthy plant growth.
Pest and Disease Risks
Onions and potatoes are susceptible to similar pests and diseases, which can spread more easily when these crops are planted together. One common pest is the onion maggot, which can damage both onion bulbs and potato tubers. Additionally, both plants are prone to fungal diseases such as fusarium and verticillium wilt.
When onions and potatoes are grown in close proximity, the likelihood of pest and disease infestations increases. For example, the spores of fungal diseases can easily transfer from one plant to another, especially during wet conditions. This can lead to widespread crop damage and reduced yields.
To minimize these risks, plant onions and potatoes in separate areas of your garden. Rotate crops annually to break pest and disease cycles, and practice good garden hygiene by removing plant debris and using disease-resistant varieties when possible.
Soil Disturbance
Potatoes require hilling, a process where soil is mounded around the base of the plants to support tuber growth. This necessary practice can disrupt the shallow root system of onions, leading to poor growth and bulb formation.
Onions have shallow roots that spread out near the surface. Disturbing the soil around them can damage these roots, reducing their ability to absorb water and nutrients. This results in smaller, less healthy onions.
To avoid soil disturbance issues, plant onions and potatoes in separate parts of your garden. This allows you to hill potatoes without affecting the onions, ensuring both crops have the best conditions for optimal growth.
Allelopathy
Allelopathy refers to the chemical interactions between plants that can affect their growth. Onions release certain chemicals into the soil that can inhibit the growth of other plants, including potatoes. This natural chemical warfare can lead to stunted growth and poor yields for potatoes.
These chemicals, known as allelochemicals, can disrupt the normal development of potato tubers and roots. This interaction makes it difficult for potatoes to thrive when planted near onions.
To prevent allelopathic effects, keep onions and potatoes in separate areas of your garden. Instead, pair each crop with compatible plants that can enhance growth and reduce pest issues. This will help you maximize the health and productivity of your garden.
Alternative Companion Planting Suggestions
Instead of planting onions and potatoes together, consider pairing them with more compatible companion plants to enhance growth and deter pests.
Good Companion Plants for Onions:
- Carrots: Carrots benefit from the pest-repelling properties of onions.
- Lettuce: Lettuce grows quickly and can be harvested before onions need more space.
- Herbs: Parsley and dill improve onion growth and repel pests like aphids.
Good Companion Plants for Potatoes:
- Beans: Beans fix nitrogen in the soil, benefiting potato growth.
- Corn: Corn provides a natural windbreak for potato plants.
- Horseradish: Horseradish repels pests like Colorado potato beetles.
By planting these compatible crops together, you can improve the health and yield of your garden. Plan your garden layout carefully to take advantage of these beneficial relationships.