How to grow Bulb Onions

• • The Bulb onion is a member of the Onion Family, and it is recommended that it should not be grown in the same soil as other family members for at least three years.

How to grow Onions - Soil Preparation

• • Onions prefer a a sunny position with a rich but light soil, however they will do well in most soils as long as it is firm.

  • For this reason it is best to prepare the soil well in advance of planting - December time is fine for maincrop onions, June is best for Japanese onions.

  • Dig the soil to 45cm (18in) deep, working in any organic matter available - remove any stones in the soil that you come across during the digging.

  • Just before planting, tread the soil down so that it is firm.

How to grow Onions - Planting Out

• • Prior to planting onions, distribute Superphosphate in the soil beneath the onions. This vital step will pay back rich dividends when it is time to harvest onions.

  • Prior to planting, prepare the growing area for onion planting. Cultivate the soil lightly with the garden fork and then rake the soil surface smooth.

  • Dig a three-inch-deep trench along the planned row of onions.

  • Spread ½-cup of granular superphosphate fertilizer into the prepared trench for each 10 feet of planting row.

  • Cover the fertilizer with 7cm (2½ inches) of soil.

  • Plant the onion seeds approximately three inches apart directly over the trench. Cover the seeds with ½-inch of soil.

  • Water the newly planted onion seeds generously. Keep the soil evenly moist while the onions establish.

How to grow Onions - Cultivation

• • Keep clear of weeds, as onions cannot compete with vigorous growing weeds.

  • Wait until the onion plants are at least three inches high. Sprinkle crystals of Sulphate of ammonia along the planting rows, using ½-cup of fertilizer for every 10 feet of planting row.

  • Work the fertilizer into the soil gently with the hand rake.

  • Water the onions generously.

  • Fertilize the onions with Sulphate of Ammonia once per month until you harvest the onions.

How to grow Onions - Harvesting

• • There's never a time when onions aren't ready for harvesting.

  • They can be picked and eaten at any stage.

  • No matter how many onions you use during the season, though, it's nice to have a crop of big onions mature at the end of summer to store for the autumn and winter months.

When to harvest

• • You can always tell when onions have stopped growing. The leaves will lose their colour, weaken at the top of the bulb and flop over.

  • Each year a few new gardeners watch the leaves die and wonder, "What's wrong?" There's nothing wrong; it's Nature's plan. The leaves' job is done - they've put the last of their energy into the bulbs.

  • Let most of your onion tops fall over by themselves - maybe 80% or 90% of them - then bend over the rest of the tops.

  • Once they're down, leave the bulbs in the ground for another 10 days to two weeks to mature fully.

  • It's not good to leave the onions in the ground for longer than two weeks after the tops die because they become open to organisms that can cause rot in storage, or they might even start growing again.

  • Pull your onions up on a sunny day if you can, then let them sit in the sun for another day or so to dry (in hot climates this usually takes just a few hours).

  • This drying kills the root system at the bottom of each bulb. The roots will be like little brittle wires when they're dry.

  • Picking the right day to pull the onions can determine how well the onions will keep. If you harvest them after some rainy weather they'll have a lot more moisture in them and won't dry out as well.

How to grow Onions - Storage and Preserving

• • After drying the onions in the open for a day or so, it's time to bring them under cover for a second, longer drying or "curing" process.

  • Some people cut the tops off the onions before curing, but that's not strictly necessary. However, if you do trim the top leaves, don't cut them any closer than 2.5cm (1") from the bulb. Otherwise the neck won't dry out, and the onion could rot in storage.

  • To cure the onions, spread them out in any warm, airy place out of the sun, such as under a carport. If you find you have too many onions for your available space, try spreading them out near the edge of your driveway, covering them with a light cotton (not plastic) sheet to provide shade. The sheet, held in place by stones along the edge, keeps the sun from burning the bulbs but still allows a lot of air circulation. Turn the bulbs a couple of times to promote even drying.

  • Heavy coverings like canvas or plastic trap moisture inside, so the onions will never get really dry. With the sheet system you won't have to worry about a few scattered rains. The sheets and the onions dry out rapidly together after a shower.

  • You don't want any wet spots on the onions when you put them in storage, so cure them really well. This can take two to three weeks. After curing them, hang the onions in mesh bags in your garage and dry them some more before putting them in your root cellar. It doesn't take this long in the South, but wherever you live, the longer you cure your onions, the better they'll keep.

Curing Basics

• • Here are the basics of curing:

    1. Sun dry for just a short time.

    2. Cure just the onions you'll store; separate the soft, young and thick-necked bulbs and use them first.

    3. Cure thoroughly in a warm, well-ventilated area away from direct sun.

    4. Don't crowd onions during curing; give them room to breathe.

    5. Onions are ready to store when the skins rattle and the roots are dry and wiry.