Regrowing food from kitchen remnants, often called “scrappy gardening,” is a simple and sustainable way to reduce waste and increase your fresh produce supply. Onions are one of the most rewarding vegetables for this method, as their root plate is biologically programmed to initiate rapid regrowth. This process is highly accessible, requiring minimal space, tools, or gardening experience to yield fresh, flavorful greens. You can turn a discarded kitchen item into a continuous source of harvestable food.
Selecting and Preparing Onion Scraps
The usable scrap for regrowth is the basal plate, the firm, flat bottom of the onion bulb where the roots emerge. Cut off the bottom portion, keeping approximately one-half to one inch of the bulb attached to this root base. The remaining bulb material contains stored energy to fuel initial new root and shoot development.
Before planting, allow the freshly cut end to dry out for a period ranging from a few hours up to a full day. This process, known as “curing” or callousing, seals the open wound of the bulb. Sealing the cut surface helps prevent the entry of pathogens and reduces the likelihood of the scrap rotting in a moist environment. The scrap is ready when the cut surface appears dry and slightly shriveled.
Initial Planting Techniques
You have two primary methods for initiating growth. Water propagation is the quickest way to see new growth, involving placing the prepared onion base root-side down in a shallow dish. The water level should be just high enough to submerge the roots but keep the main bulb tissue dry to prevent rot.
Direct soil planting offers a more stable and nutrient-rich environment for long-term growth. To plant directly, use a well-draining potting mix in a container or a garden bed. Plant the onion scrap about one to two inches deep, ensuring the cut top of the bulb remains exposed above the soil surface. Soil-based growth tends to produce thicker, more robust green shoots because the plant can draw more sustained nutrition.
Ongoing Care and Harvesting
Once the scrap is established in soil or water, it requires consistent care to maintain production. Onions are sun-loving plants and need a location that receives a minimum of six hours of direct sunlight each day for optimal growth. If growing indoors, a south-facing windowsill is typically the best option to meet this light requirement.
Whether in soil or water, the growing medium needs consistent moisture, but never saturation. Soggy conditions will quickly lead to root rot, so only water the soil when the top inch feels dry to the touch. For scraps in water, refresh the water every two to three days to ensure oxygenation and prevent the buildup of bacteria or mold.
The primary harvest from regrown onion scraps will be the green tops, which function exactly like scallions or spring onions. These greens are typically ready to harvest when they reach about four to six inches in height, often within one to two weeks after planting. Harvest by snipping the outer leaves with scissors, leaving the central shoot intact to allow for continuous regrowth. While it is possible to grow a full new bulb, this requires significantly more time, usually three to four months, and involves leaving the greens completely uncut so their energy can be channeled into bulb development underground.