How to Get Onions to Make Big Heads

Grow bigger onions in the home garden.
Grow bigger onions in the home garden. (Image: Images)

Onions are grown in many home gardens. This versatile vegetable is used in many recipes and it adds flavor. Growing onions in your own garden is healthier, because you control the type of fertilizer and/or pesticides that are used. To get your onions to grow big heads, you need a garden site that receives 14 to 16 hours of sunlight. If you want to grow onions as big as or bigger than you can buy at the store, there are a few ways to improve your success.

Things You'll Need

  • Tiller or garden fork
  • Onion sets
  • Compost
  • Garden rake or hoe
  • Insecticide
  • Multipurpose fungicide

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Choose a sunny location to plant and grow the onions.

Till or dig up the garden with a garden fork to a depth of 12 inches. Do this as early in the spring as possible, or it can be done in the fall.

Amend the soil with 3 to 4 inches of compost. The onion bulb needs loose fertile soil to grow.

Examine the onion bulb. One end will have a pointed tip which is the top and the other end will be flat for the root section. Oftentimes, there are small roots already growing at the bottom end.

Separate the big onions from the smaller onion bulbs. If you want to grow big onions, plant the bulbs that are smaller than a dime.

Plant the onions root side against the soil to a depth of a half-inch. Space the onions 4 inches apart and space the rows 12 inches apart. Do not bury the onions, because that produces small table onions.

Pull the weeds, because onions do not grow well with competition. The weeds will take up the moisture and nutrients that the onions need to grow.

Cultivate the soil with a small garden rake or hoe, around the onions, to keep the ground loose. This allows the bulb to expand without being constricted by the soil. Be careful that you do not damage the onion bulb.

Water the onions. Every week, give the onions 1 inch of water.

Feed the onions when they are 6 inches tall. Mix and apply fertilizer according to label directions. Fertilize the onions again when the bulbs start to grow. Wait until the tops fall over before harvesting.

Check the onion plant for pests such as the onion thrips. These insects are light brown in color and are just visible with the naked eye. They feed on the leaves and such the liberated juices. Spray the onion plants with an insecticide made to use on onions.

Watch for blight, when the leaves turn a pale green then change to yellow and purple blotch; you will notice purple lesions on the leaves. Blight is prevented by planting all the rows in the same direction and having the onions planted in an open area. If you cannot stop the problem, then spray the onion plants with a multipurpose fungicide. Mix and apply according to label directions.


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