If you want to grow onions, but don't want to dig up your garden, use a grow bag. They are simple to construct, easy to use, and help keep out some of the pests that can attack onions in the ground. Onions are a simple crop to grow, and you can eat them at any stage once they start growing, either as spring onions or full-sized onions.
Buy or make a grow bag for the onions. You can buy grow bags from garden centres or online. If you want to save money, there are two types of simple grow bags to make. Make one using black plastic from a hardware shop, or use a heavy-duty bin bag. If you make your own, put plenty of holes in the bottom of the plastic for drainage. Your onions will rot without proper drainage.
Pour the bag of potting soil and compost into the wheelbarrow. Use the hoe to mix the soil and compost together.
Fill the grow bag with at least 30 cm (12 inches) of soil. Fill the bag all the way to the edges. If you are using a bin bag, roll the top of the bag down until the top of the bag is about 5 cm (2 inches) over the top of the soil. This stops the plastic from covering the onions and hindering their growth.
Plant the onion bulbs or seeds. If you are planting onion bulbs, plant them at least 2.5 cm (1 inch) below the surface of the soil. If you are planting seeds, mix the seeds with about 125 ml (1/2 cup) of sand, and sprinkle the seed mixture across the top of the soil.
Water the onion bulbs or seeds, and then wait for them to start growing.
Allow the onions to grow until they reach the desired size. You can start picking the onions when they reach about 15 cm (6 inches) above the ground. Smaller onions are typically milder and sweeter than full-sized onions.
Water your onions every other day to avoid over-watering. If onions stay too wet they will rot.