The onion (Allium cepa) is a cool-season vegetable that first appeared in Asia, and later was commonly used in ancient Greece and Egypt. Throughout time, methods of cultivating onions have become more refined. Onions grow best in areas with full sun and well-draining, loose soil. They are heavy feeders, requiring fertile soil and multiple applications of fertilizer. Planting onion starts with a dose of fertilizer high in phosphorous will jump-start their growth. Successive fertilizer applications will continue to promote healthy growth.
Spread a 1- to 2-inch layer of compost over the planting site. Mix the compost into the top 6 to 8 inches of soil using a rototiller. Smooth the soil surface using a rake.
Dig a 4-inch wide and deep trench with a trowel. Sprinkle a 10-20-10 granular fertilizer in the bottom of the trench at a rate of 1/2 cup per 10 feet. Add 2 inches of soil to the trench, covering the fertilizer. Pat the soil in the trench down firmly.
Place the onion starts in the bottom center of the trench, spacing each start 4 inches apart. Position the onion starts with their rounded ends down and their pointed ends facing up.
Backfill the trench with soil, covering the onions completely. Tamp the soil down gently over the onions. Water the planting to a depth of 6 inches using a garden hose.
Fertilize the onion starts a second time when their bulbs begin to swell and their foliage reaches 3 inches tall. Apply a 5-10-10 granular fertilizer at a rate of 3/4 pound per 25 linear feet of row. Dig a 1-inch deep trench down either side of the growing row of onions. Space the trenches 2 to 3 inches away from the center of the onion row. Measure out the correct amount of fertilizer and divide it into two equal portions. Pour one portion of fertilizer evenly along the bottom of the left trench and the second portion evenly along the bottom of the right trench. Backfill each trench with soil. Water the area thoroughly to activate the fertilizer.
Things You Will Need
- Shovel or trowel
- 10-20-10 granular fertilizer
- Garden hose
- 5-10-10 granular fertilizer
- Rodale's Vegetable Garden Problem Solver: Fern Marshall Bradley
- National Gardening Association: Soil Prep for Alliums
- Texas AgriLife Extension Service Aggie Horticulture: Onions
- Sunset: Onion
- Jupiterimages/Photos.com/Getty Images