How to Grow Onions
The basis of so many delicious dishes, onions (Allium cepa) are an essential ingredient in every cook’s store cupboard. With so many tasty types of onions available, why not grow your own and try some of them out? Follow our simple guide to growing onions.
Onions grow best in a sunny, open position with well-drained soil and a long, cool growing season. They can be grown from seed or seedlings, but choosing the right variety for your climate is important, as onion bulb formation is influenced by both day length and temperature. Once they're growing well, onions are a low-fuss crop that simply need steady care, enough space to form bulbs and patience until the leaves begin to yellow and fall over at harvest time
Top 5 steps to growing onions
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Grow onions in full sun through the cooler parts of the year.
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Prepare well-drained soil with organic matter before sowing or planting.
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Grow onions from seeds or seedlings, choosing varieties suited to your climate.
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Thin or space seedlings so each onion has room to develop a good bulb.
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Harvest onions when the leaves yellow, soften and fall over.
Essential shopping list
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Onion seeds or seedlings
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Scotts Osmocote® Controlled Release Fertiliser: Tomato, Vegetable & Herb
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Organic mulch
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Garden trowel
Planting and harvesting onions in Australia
Plant onions in early to mid spring in most climates. In warm climates, plant onions in autumn.
Harvest onions between summer and autumn in most climates. In warm climates, harvest onions in late spring.
The best onion types to plant
With so many types of onions available, it can be difficult to choose which one to grow! Here are a few of our favourites:
- Onion ’Gladalan Brown’: a large early cropping, brown-skinned heirloom variety; very reliable.
- Onion ’Gladaland White’: an heirloom medium to large white onion.
- Onion ’Ailsa Craig’: mild tasting, straw-yellow coloured, large Spanish type.
- Onion ’Long Tropea Red’: purple or red heritage variety with mild, sweet flavour
- Onion ’Odourless’: pale brown skin and mild flavour; has no smell.
- Creole
- Transylvanian
Essential equipment for growing onions
To grow onions at home, you will need:
- Onion ‘sets’ (young onion bulbs) or seedlings
- Spade
- Fork
- Supply of Scotts Osmocote® Compost Premium Soil Improver
- Scotts Osmocote® Controlled Release Fertiliser: Tomato, Vegetable & Herb
- Scotts Osmocote® Plus Organics Tomato, Vegetable & Herb Potting Mix
- Netting
When to plant onions in Australia
Some onion varieties can be planted in autumn for an early summer harvest, but there is a chance the bulbs may rot in heavy soils that remain wet over the colder months. The best time to plant onion sets is in early to mid-spring.
Onions need rich, fertile pH neutral or mildly alkaline (6.5 to 7.5) soil in full sun. To prepare the soil for spring planting, dig in lots of Scotts Osmocote® Plus Organics Tomato, Vegetable & Herb Potting Mix, Scotts Osmocote® Compost Premium Soil Improver or well weathered animal manure in autumn and leave it to settle over winter.
How to plant onions
Although you can grow onions from seed, it’s simpler to grow them from ‘sets’. Sets are young onion bulbs, grown especially for planting.
- Before planting onions in spring, dig over the plot to break up the soil and clearing it of all weeds. Tread down the soil to lightly compact it and rake over to produce a level surface with a light, crumbly texture.
- A couple of weeks before planting your onions, rake in a Scotts Osmocote® Controlled Release Fertiliser: Tomato, Vegetable & Herb at the rate recommended on the bag or container.
- Plant onion sets 20cm apart, with the tips of the young bulbs just showing above the soil. Follow label instructions for planting seedlings. Allow 30cm between rows.
- Water in after planting – this helps to settle the soil around the new plants.
- Cover the area with netting to stop birds pulling up the young plants.
☀️ HOW TO GROW ONIONS IN WESTERN AUSTRALIA CONDITIONS
Now is the ideal time to plant out the onion tribe and yes there are plenty of them. Included are red and brown regular onions, red or white salad onions, spring onions, chives round leaf and garlic types (there's a range of different forms here too), leeks as well as obscure types such as walking onions and Welsh onions.
What's needed is a sunny open location and free draining soil, which is easy for most of us living on sand. Sow seed in punnets or trays into a seed raising mixture. Alternatively plant seedlings direct into your garden bed of prepared soil. Garlic cloves and shallot sets are planted direct. Avoid fertiliser rich soil - rather add Baileys Soil Improver Plus. Onions, leeks and garlic take up to 6 months to mature. Spring onions take about 6 weeks before harvest where chives can be continuously cut over a number of years.
How to Take Care of Onions
Follow these tips for a good onion harvest:
- Keep the plot weed-free. Hoeing between rows risks damaging foliage and bulb tips, so weed by hand where possible.
- Water regularly in dry periods.
- Remove any flower spikes as soon as they appear.
- Stop watering once the leaves start yellowing – this means that the bulbs are starting to swell.
How to harvest onions
Spring-planted onions should be ready to harvest in late summer and early autumn. In warmer areas, autumn-planted onions will be ready to harvest from early to mid-summer. Once the foliage starts to yellow and bend over, the bulbs are ready to harvest. Use a fork to carefully lift them, taking care not to penetrate or bruise the bulbs.
Storing onions
- Place the bulbs in a single layer on a drying rack or on a slatted shelf that allows air to circulate around them.
- Leave them outside in the sun or under a patio or veranda roof for a couple of weeks to dry.
- Once the skins are dry and papery, store the bulbs in net bags or plait the foliage to form bundles.
- Store in a light, cool and well-ventilated spot. Bulbs stored in the dark are more likely to sprout.
Common onion pests and diseases
| Onions bolting |
Bolting occurs when onions stop developing their bulbs and instead produce flowers. It can be triggered by stress, such as sudden dry period or cold snaps. Onions that have bolted can’t be stored but are still edible.
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| Onion white rot |
Onion white rot is a soil-born fungus that causes leaves to yellow and wilt, and bulbs to rot.
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| Leek rust |
Leek rust is a fungal disease which can affect all alliums. It appears as orange spots on leaves. and is more likely in wet conditions. Heavy infections can affect yield.
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