The practice of growing different crops in close proximity to maximize garden health and productivity is known as companion planting. This method takes advantage of beneficial interactions between species, which is a common strategy in both small home gardens and large-scale farming. A frequent query among gardeners is whether alliums and tubers, specifically onions and potatoes, can be successfully combined in the same growing space. This pairing is not only possible but is often recommended by horticulturalists, provided specific planting and maintenance techniques are followed.
The Companion Planting Relationship
Onions and potatoes are considered good neighbors because their growth habits and resource needs are complementary rather than competitive. Potatoes develop their tubers deep within the soil, typically requiring a planting depth of six to eight inches for optimal growth. Conversely, onions are shallow-rooted bulb crops that primarily utilize the top layer of the soil, often planted only about an inch deep. This difference in root structure minimizes underground competition for water and nutrients, allowing both plants to thrive.
The primary benefit of this interplanting strategy is the natural pest deterrence provided by the onion. Alliums emit a distinct sulfurous aroma that helps mask the scent of potato foliage. This camouflage is effective in discouraging common potato pests like the Colorado potato beetle and various species of aphids. The presence of alliums can reduce pest populations, contributing to healthier potato plants.
Optimal Interplanting Techniques
Successful interplanting depends heavily on precise physical arrangement to ensure both crops receive adequate sunlight and space. The most effective technique involves planting the onions in the spaces between the rows or hills of the potatoes. Potatoes should be spaced approximately 10 to 12 inches apart in the row, with rows about 36 inches apart, which provides ample room for the onion sets.
Placement and Timing
Planting the onions on the outer perimeter is preferred since potato plants develop a dense, bushy foliage canopy. Placing the shallow-rooted onions on the edges ensures they receive sufficient sunlight and are not heavily shaded by the larger potato plants. Onion sets, spaced about six inches apart, should be planted earlier than the potatoes, or at the same time, to establish them before the potato vines grow large.
A common arrangement is to plant the potatoes first, then create a ring or border of onions around the central potato plants, especially in raised beds. A separation of at least 12 inches between the two crops is advisable to give both root systems room to expand. Using early-season potato varieties with mid-season onions can help stagger the peak growth and harvest periods, further reducing resource competition.
Managing Competition and Needs
Potatoes are known as heavy feeders that require significant amounts of nutrients, particularly nitrogen and potassium, throughout their growing cycle. Onions, while more frugal, also need consistent nutrition to form large, healthy bulbs. It is necessary to start with soil enriched with compost or well-rotted manure to meet the high initial demands of the potatoes.
Watering Requirements
Watering requires a careful balance, as both crops have specific, yet slightly differing, needs. Potatoes require consistent moisture, about one to two inches of water per week, to develop properly formed tubers. However, the shallow-rooted onion bulbs are susceptible to rot if the soil remains waterlogged for extended periods.
Hilling Maintenance
A significant maintenance consideration is the practice of hilling, which involves mounding soil or mulch around the base of the potato plants as they grow. This is done when the potato foliage reaches about six to eight inches tall to encourage more tuber formation and protect the developing potatoes from sunlight. Hilling must be performed carefully to avoid disturbing the shallowly planted onion bulbs, which could damage the crop.