The answer to whether green onions grow from onions is yes; they are often the same plant harvested at different stages of its life cycle. “Green onion,” “scallion,” and “spring onion” refer to the young, immature stalks of the bulb onion species, Allium cepa, or the non-bulbing species, Allium fistulosum. In both cases, the green tops are the leaves of a plant within the Allium genus. The primary difference lies in when the plant is harvested and whether it belongs to a variety that forms a large, underground storage bulb.
The Botanical Relationship: Green Onions Versus Bulbs
A typical bulb onion, such as a yellow or red onion, begins as a seed that grows into a small green shoot. This young plant is anatomically a green onion, characterized by its long, hollow leaves and a small, white, non-enlarged base. If a bulbing variety of Allium cepa is harvested at this early stage, it is considered a green onion or spring onion. The plant has not yet accumulated enough energy to swell the base into the layered storage structure known as the mature bulb.
If left in the ground, bulbing varieties continue to mature, shifting energy stores from the leaves to the underground bulb, causing it to expand. Conversely, the type of green onion known as a scallion often belongs to Allium fistulosum, or a bunching variety of A. cepa, which does not form a large bulb. These non-bulbing types maintain a straight, slender white base throughout their growth, making them suitable for continuous harvest. This distinction explains why some green onions have a slight bulb at the base, while others are uniformly straight.
Quick Harvest: Regrowing Green Onion Scraps
The white, root-end scraps of store-bought green onions are the viable base of the plant and can be easily regrown for a continuous yield. To begin, save the bottom one to two inches of the white portion, ensuring the fibrous roots are intact. Place these bases upright in a narrow glass or jar and add cool water, enough to submerge the roots but leave the cut top edge exposed.
Positioning the glass on a sunny windowsill provides the necessary light for photosynthesis, powering the plant’s regrowth. New green shoots typically emerge from the center of the white base within a day or two. Refresh the water every few days to prevent mold or bacteria growth, which can cause the roots to rot. Harvest the new growth once the shoots reach four to six inches by snipping them off, leaving an inch of new growth to allow for further regeneration.
This method works because the plant uses the remaining stored energy in the white base to produce new leaves. While regrowing in water offers a rapid harvest, the flavor and thickness of the shoots will diminish over several cycles. For a longer-term supply and thicker stalks, transfer the rooted bases into a pot filled with well-draining potting soil after one or two water harvests. Planting them in soil allows the plant to draw nutrients, sustaining more robust growth.
Forcing New Greens from Mature Onion Bulbs
Another way to produce green tops is by utilizing a mature bulb onion, such as one that has begun to sprout in the pantry. This method forces the dormant bulb into its vegetative growth phase to produce edible green shoots. Start by cutting a thin slice from the bottom of the bulb, including the root plate, and placing it in a shallow container of water, similar to regrowing scraps.
The mature bulb acts as a large energy reserve, which the plant draws upon to quickly push out new green leaves through the center. Alternatively, plant the entire sprouted bulb into a pot of soil, covering it lightly so the tip of the sprout remains just above the soil line. Within a week, the green shoots will emerge and grow rapidly, offering a substantial harvest of tender greens.
These greens tend to have a slightly more intense flavor compared to those of a true scallion. The key difference from the scrap method is that the mature bulb will eventually be depleted of its stored energy, becoming soft and unusable. This technique is an excellent way to salvage a sprouting onion and enjoy a final, flavorful harvest.