Growing Onions From a Cutting
The onions is the plant that keeps on giving. Many varieties of onion provide a renewable resource, sprouting again and again from portions you may otherwise discard. Part of the onion is used for culinary purposes, while the base, properly cared for, grows a fresh onion, ready for the cycle to begin again. Resprouting onions is a fun and resourceful way to grow and gather food again and again. Use organic onions for healthiest results.
Growing Scallions From Cuttings
Cuttings from the green onion (Allium fistulosum), sometimes called scallion or spring onion, resprout and grow quickly in a vase of water. When cutting green onions or scallions for a recipe, leave 1.5 to 2 inches intact on the white bottom portion. Note the very bottom looks a bit like plant roots; in fact, these are the onion's roots. Place these in a vase or glass of water, enough to cover the roots, and set in a sunny location. If the water gets murky, dump it and replace with fresh water. In about two weeks, you'll have a fresh batch of fully grown green onions.
To regrow green onions in soil requires less than half an inch of the bottom of a green onion. Buried in 2 inches of soil and watered frequently, a cutting from one onion will produce an entire bunch of onions. As with scallions planted in water, you can start harvesting greens within a couple of weeks.
Growing Larger Onions
Larger onion varieties sold in grocery stores can be grown from roots as well. Cut the bottom or root end off any onion that has visible roots protruding from the end. Plant the onion cutting just beneath the surface of soil in a sunny and warm location, and in just a few days this will sprout new growth. The onion bulb has finished growing when its stalk starts to yellow and lean over, which may take 90 to 120 days.
Regrowing Leeks from Cuttings
Leeks, similar to and pungent like the onion, can also be grown from cuttings. The root end of leeks regrow in water in much the same manner as green onions grown in water. The new, green growth on leeks is cut and used much like onion greens whenever needed for a recipe.
If you want to grow a full-sized leek that can be used in the traditional way, for its white portion, you'll need to grow the regenerated plant in soil. Plant the leek outdoors in a shallow trench, or indoors in a container with the soil scooped away to make a depression in the middle. To "blanch" the leek, and give it its long white bulb, mound the soil around your leek as it grows. The portion that's protected from light by the soil will stay pale.
Harvesting Your Onions
Once an onion, whether green or a larger variety, is planted and growing, its shoots can be used any time you need them. Cut off what you need and they will grow tall again, much like grass. This process also works with green or thin onion varieties grown in water.
Most green onions will form tight clusters or "bunches" of bulbs as they grow. These bunching onions can be harvested one at a time, as you need them, if you're careful not to disturb the others too much. Full-sized onions with large bulbs can be harvested once the tops die back, a sign the plant has put all of its resources into the bulb. You can use them immediately, but if you'd rather store your onions for a few weeks or months they must be allowed to "cure" and dry for a couple of weeks. Then they can be stored in a cool, dry, well-ventilated location until they're needed.