Yes, onions and garlic can be planted together, a successful strategy for home growers. Both belong to the Allium genus, meaning they share many cultivation preferences and growth habits. Successfully co-planting them requires understanding their common needs and providing adequate space to prevent competition. This maximizes space efficiently while benefiting from the natural interactions between these two aromatic vegetables.
The Compatibility of Alliums
The success of planting garlic and onions near each other stems from their mutual environmental requirements and beneficial companion planting dynamics. Both thrive under similar conditions, making them convenient to manage in the same garden area. They also share a defense mechanism through distinctive sulfur compounds released into the air and soil.
The strong, pungent odors of the Allium family are thought to confuse or repel many common garden pests. Garlic, for example, is known to deter onion thrips and aphids. This natural pest control can potentially reduce the need for chemical intervention. However, because they are closely related, they share susceptibility to specific diseases, such as white rot (Sclerotium cepivorum). Proper spacing and crop rotation are necessary to prevent this shared vulnerability from affecting the entire planting.
Essential Growing Requirements
To ensure both onions and garlic grow well together, the soil must meet a specific set of requirements they both share. Both are heavy feeders and require a loose, well-draining structure, ideally a sandy-loam or silt-loam. This structure prevents waterlogging, which can lead to bulb rot. Incorporating high organic matter, such as aged compost or manure, prior to planting provides necessary fertility and improves soil texture.
The soil’s pH should be slightly acidic to neutral, typically ranging between 6.0 and 7.0. They require full sun exposure, meaning a minimum of six to eight hours of direct sunlight daily for bulb development. Consistent moisture is necessary due to their relatively shallow root systems. However, the soil must never remain waterlogged, especially as the bulbs begin to mature.
Practical Planting and Spacing
The physical arrangement of onions and garlic requires careful consideration due to their shared need for nutrients and space. The planting material for each differs, impacting the timing and depth of installation.
Planting Materials and Timing
Garlic is typically planted in the fall from individual cloves, placed root-end down about one to two inches deep. Onions are usually planted in the early spring from small, immature bulbs called sets or from transplants. These are placed much shallower, with the top of the set barely covered by soil.
Spacing Requirements
Competition for resources is the primary concern when co-planting, so sufficient distance must be maintained between developing bulbs. Planting them too closely results in significantly smaller harvests for both. A minimum of six to eight inches of space between each plant is recommended to allow bulbs to reach their full potential. For maximum bulb size and to mitigate the risk of shared diseases like white rot, a spacing of up to twelve inches is advisable, with rows spaced eighteen inches apart. Staggering the planting times—garlic in fall and onions in spring—can also help manage resource demand throughout the growing season.