Grow large onions by choosing the right variety, planting in the right location, preparing the soil, planting the seeds, watering the plants and fertilizing the onions. Use onion seeds, a garden trowel, compost and fertilizer.
- Choose the right variety
Choose an onion variety that grows large bulbs, such as intermediate or short-day.
- Choose a good location
Choose a planting site that receives a lot of sun.
- Prepare the soil
Till the top 10 inches of soil into a fine texture, breaking up any large chunks. Work 3 inches of compost into the top 6 inches of soil. Dig a long 2-inch deep trench, and sprinkle 1/2 cup of superphosphate fertilizer along it. Fill in the trench with dirt, tamp down the soil and water the planting bed.
- Plant the onion seeds
Poke the onion seeds into the soil just above the fertilized soil. Make sure the seeds are no deeper than 1/4 inch. Cover the seeds with soil.
- Water the plants
Gradually give the plants 1 inch of water over the course of a week.
- Fertilize the onions
Feed the onions with a granular 21-0-0 fertilizer every month by digging a trench and sprinkling it in the bottom of the trench. Do not apply the fertilizer directly to the bulbs, as this can burn them.