Yes, you can plant an onion that has sprouted in your pantry or on your counter. The green shoot signals the onion is resuming its natural life cycle. Onions are biennial plants, meaning they complete their growth over two seasons; the bulb is the first year’s energy storage, and the sprout signals the start of the second phase—reproduction. This process is triggered when the bulb senses warmth and moisture, signaling the end of its dormant period. Planting the sprouted bulb allows the onion to grow leaves, flower, and produce seeds.
Preparing the Bulb for Planting
Before planting, inspect the bulb for any signs of decay, such as soft spots or mold. The most effective method is to separate the individual growth points within the bulb to maximize yield. A single large onion often contains multiple distinct sections, each with its own central sprout and root base, which you can gently peel or slice apart.
Remove the papery outer layers until the individual green sprouts are visible and can be separated. Each separated section should retain a portion of the original root plate to ensure it can establish itself in the soil. Planting these smaller sections individually prevents competition for space and nutrients, avoiding smaller, misshapen bulbs. If a separated sprout lacks roots, encourage growth by placing its base in a shallow cup of water until new white roots appear.
Planting Location and Technique
Onions thrive when planted in a location that receives ample sunlight. The soil must be well-draining and loose, as onions are susceptible to rot in waterlogged conditions. If your native soil is dense or clay-heavy, incorporating well-aged compost or planting in a raised bed will significantly improve drainage and nutrient availability.
When planting the prepared sections, create small holes deep enough to cover the root plate and the base of the bulb. The green sprout tip should remain exposed above the soil surface for photosynthesis. Space the individual sprouts at least three to four inches apart to give each new plant sufficient room. After planting, water the area gently but thoroughly to settle the soil around the roots, ensuring the soil remains consistently moist but not saturated during establishment.
Expected Results and Harvesting
Planting a sprouted onion results in the production of green onion tops, which are essentially scallions. The plant allocates the bulb’s stored energy into producing these long, hollow leaves for photosynthesis. You can harvest these greens continuously by snipping them off about an inch above the bulb, allowing for multiple harvests without disturbing the underground growth.
A planted grocery store onion is focused on reproduction, meaning it is unlikely to form a new, single, large bulb. Instead, the plant will eventually “bolt,” sending up a single, thick central stalk that culminates in a flower head. Allowing the plant to complete this process results in the production of seeds, which can be harvested for future planting. If you are aiming for a secondary bulb harvest, dig up the plant approximately 60 to 80 days after planting, right as the green tops begin to yellow and die back.