What to Do With Onions in April for Large Bulbs and Pest-Free Plants

April is usually a developmental month in the onion-growing season, but it is also not too late for any gardeners who have yet to plant their crop. I’ve grown onions for years, and here I reveal some key tasks gardeners should do this month that will help bring you a fantastic harvest come summer and early fall.

Firstly, there is still time to plant onions in April if you haven’t yet, but you should act quickly as the clock is ticking. However, if you started growing onions in the fall or early spring, your plants should be happily developing shoots. It makes April a month to weed, feed, water as required, and protect your crop from pests.

I usually plant my onions in the spring. I have both sown seeds indoors in winter and planted sets outdoors in early spring over the years. I have found that giving onions attention early in the season gives the crop a much-needed boost, rewarding you with good-sized bulbs come harvest time. Here are my tips for what to do with onions in April:

1. You Can Still Plant

The window is still open to plant onions, but it is closing. Mid-April is the latest you want to be planting onions to have any hope of a decent summer harvest. Sets are the quickest and easiest way to plant onions this month, though you can still sow seeds.

If I were starting my onions this month, I would opt for onion sets rather than seeds. Sets are really simple to plant, just push them into the soil 4-6 inches apart so the tip is just showing above the surface. It often helps to cover sets with fleece or netting after planting to stop birds from pulling them out of the ground.

You can get a collection of red, white, and yellow onion sets at Burpee to plant

You can continue to plant onion seeds outdoors up to mid-Spring, planting thinly in rows a half-inch deep and thinning the seedlings to four inches apart as they develop. However, crops from seeds won’t enjoy as long a season, so the bulbs are likely to be smaller.

See the range of onion seeds at Amazon

See the range of onion seeds at Walmart

See the range of onion seeds at Botanical Interests

2. Weed Your Crop

Onions are hungry crops, and sensitive ones too. They don’t like lots of competition from weeds for water and nutrients. Too many weeds can result in smaller bulbs when it comes time to harvest your onion crop.

Spring is a time when weed seeds germinate easily and quickly in moist soils and warming days. Getting on top of weeds early is advisable, so they do not reseed and spread even more seeds to deal with.

This month, commit some time to getting rid of weeds from your onion bed. A bit of dedication now can reduce the weed pressure for the rest of the season.

Remove deep-rooted weeds by hand – ensuring to remove the roots completely for troublesome perennial weeds - and regularly use a garden hoe to slice smaller, annual weeds on warm days.

A weeding tool like this from Amazon will help you lever even troublesome weeds out of the soil with ease

3. Water During Dry Spells

Onions like consistently moist soil throughout the season. In spring, the famous April showers will often provide the inch of water that onions need per week. However, in drier Aprils, you may need to irrigate your onion beds to prevent the soil from drying out completely.

It is a careful balancing act to get right. The soil needs to be moist, but not saturated. Overwatering is a common onion-growing problem that can leave the crop susceptible to fungal or bacterial diseases, or even cause the plants to rot in the ground in extreme circumstances.

Aim for regular, infrequent deep watering when required this month. This approach to watering plants is better than little and often.

Drip irrigation systems or soaker hoses can deliver water directly to the root zone, rather than soak the foliage, which can leave the crop susceptible to fungal diseases, like powdery mildew.

You can get a 25 ft soaker hose at Walmart to slowly release water directly to the plant's roots.

4. Feed Crops With Nitrogen

How you fertilize onions in April depends on the stage of the season your crop is at.

If you are only at the planting stage, focus on enriching the planting site with organic matter, such as compost or well-rotted manure. Adding organic compost, like this compost at Lowe’s, to the ground will help the crop get off to a great start.

However, if your crop is a bit further along, it may be time to give plants their first dose of a nitrogen-rich feed.

An application of nitrogen around three weeks after planting the crop helps to fuel the growth of foliage. This, in turn, helps you grow bigger onions by aiding the development of bulbs later in the season. You can continue to feed every 2-3 weeks until bulbing begins.

Side-dress the crop by making a furrow a few inches from the vegetables, into which you sprinkle the fertilizer and water it in well. Blood meal offers a good organic option for feeding onions, and you can get bags of blood meal at Burpee.

Only apply the feed at the recommended rate, and don’t give the crop excess nitrogen once bulbing starts, as it’ll encourage the development of foliage rather than the bulb.

5. Prevent Pest Damage

The likes of allium leaf miner and onion maggot (onion fly) can be troublesome pests of onion crops. Along with thrips, aphids, and cutworms, pests can attack both the foliage and the bulbs.

This month, keep a close eye out for the signs of pests, including distorted foliage, small holes in the leaves, or seedlings cut down at the soil level. The smaller pests, such as thrips or aphids, can be dealt with by spraying insecticidal soap. You can get ready to use insecticidal soap at Walmart.

However, a greater overall level of protection can be offered by covering the crop with insect-proof mesh in spring to keep unwanted pests away from the plants. You can get ultra-fine netting at Amazon to protect your crop from pests.

Also, consider onion companion planting to reduce pest problems when planting the vegetable garden this month. Using aromatic herbs for companion planting can attract beneficial insects and natural predators of many typical onion pests.

It is also worth keeping an eye out for slugs and snails. One year, I had my onion crop decimated by slugs in spring, which chewed the green tops. I had never known slugs chomping on onions before; it was an eye-opener.

To stop your crop from being affected, there are slug control methods to put in place, including physical barriers, rough surfaces around the plants, or beer traps that will tempt slugs from the crop.

What to Shop

If you spot an onion in your cupboard sprouting this spring, did you realize you can plant it in the garden and grow a new bulb? It offers a great sustainable decision to regrow the sprouting section, rather than throw it in the trash.

This guide on how to plant a sprouting onion takes you through the whole process, from removing the sprouts to planting, caring, and ultimately harvesting the new bulb.

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