Why Are My Onion Tops Curling and Wilting?
Onion tops naturally curl and wilt at the end of the growing season. If they’re wilting early, they may be experiencing damage from pests, diseases, or improper care. Learn why onion tops curl and wilt alongside seasoned grower Jerad Bryant.
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The last thing you want is for your onions to fail before you harvest them! Curling, floppy tops are an unwelcome sight during the growing season. Catch the problem early, and you’ll have healthy, bulbous onions by the end of the season.
Though wilting tops are unwelcome when they’re premature, they’re perfectly normal at the end of the season. The normal time for leaves to wilt depends on the planting time and onion type. Three main types of onions exist: short-day, intermediate-day, and long-day.
Know your onion’s variety and type so you can watch for curling tops at the right time. So, let’s answer the question: why are your onions’ tops curling and wilting?
The Short Answer
Onion tops normally curl as they finish growing at the season’s end. They curl ahead of this harvesting window because of diseases, pests, or improper care. Wrong planting times and dry soil can cause yellowing leaves and a lack of healthy growth.
Ensure your onions have what they need during the winter or spring, and they’ll produce healthy bulbs with sweet flavors and crisp textures.
The Long Answer
Onions experience wilting tops or floppy leaves due to a wide range of conditions! Inspect your garden, manage the site, and look closely at your onion crop. Though these symptoms are normal, seasonal responses, they also occur because of thrips, viruses, and improper soil moisture levels.
The Normal Growing Process
It’s normal for onion tops to wilt and fall over if it’s the end of their growing period. Short and intermediate-day onions, planted in the fall, mature over the winter and spring. Long-day onions, planted in late winter, finish growing in the summer.
While short-day types work well in southern states, long-day types are best in the northern ones. Intermediate-day onions work well in between. If their tops turn yellow and brown and fall over when they should, do not panic! It’s completely normal.
Too Much Water
Excess water is difficult for onion roots to handle. They drown without access to air, turning mushy and brown. As they die out, the tops begin yellowing before turning mushy and falling over.
Rich, porous, and absorbent soil is crucial for maintaining a moist culture. Dense clay is particularly difficult to grow these bulbs in, as it doesn’t drain well. Plant them in a well-drained loamy mix for the best results.
Not Enough Water
Like excess moisture, not enough water is also deadly for growing crops. Dry, withering roots trigger yellow leaves, browning tips, and wilting onion tops. Ensure the soil stays consistently moist, but not soggy, during the growing season.
One easy way to conserve soil moisture is with organic mulches like compost, leaf mold, or straw. They protect the ground and feed it with nutrients and microbes. Mulches are also absorbent, soaking up excess moisture and keeping it where the roots need it most.
If soil moisture is an issue, add a layer of compost two to three inches thick. Leave a gap between the plants and the mulch, but place it near their roots so they can access the benefits.
Thrips
Thrips are one of the many pests that afflict precious crops. They’re tiny, hopping insects with sucking mouthparts. They cut holes in the leaves, inject their saliva, and lap up the juices that come out of the foliage.
You can have thrips and still grow a successful crop, so long as the infestation isn’t excessive. The real danger with thrips is their disease-spreading tendencies. They’re hosts for a wide range of afflictions that cause wilting symptoms.
Thrip damage shows up as stippling on the leaves. Watch for white flecks and streaks on onion tops, young stems, and seedlings. You may see the yellow hopping adults when large populations are present.
Yellow Dwarf Virus
This virus spreads through aphids and infected plants. It’s a nasty disease that causes yellow markings and crinkly, flat leaves. It’s deadly for young seedlings, though adults may still form small bulbs.
Watch for yellow streaks on young leaves. The yellowing spreads over time, forming long streaks and completely yellow tops. Prevent it by using disease-free onion sets at planting, and watch for aphids in the spring garden.
If you see signs of this virus, pull the infected plants and discard them away from the veggie beds. Bury them, hot compost them, or throw them in your green-waste bin.
Aster Yellows
Aster yellows is a bacterial condition that causes twisted, flat leaves with yellow-green markings. It infects a wide range of crops, from asters to onions! Yellowing often starts at the base of young leaves and spreads upwards.
Prevent this condition by controlling the insects in your garden. It’s most often spread by the aster leafhopper, a pest-like critter that hops from plant to plant. Keep them away with row covers while they’re most active, and pull any plants as soon as you identify this bacterium on them. Plant a diverse array of flowering plants to attract leafhopper predators, like spiders, wasps, and robber flies.
Nematodes
Nematodes, like thrips, are pests that target growing plants. These worm-like critters infest bulbs, roots, and stems to cause a wide array of issues. They’re impossible to see with the naked eye, though they cause damaging symptoms that are possible to see.
Look for twisted, curling, and stunted foliage. The bulbs will be lightweight instead of heavy and full, and they’ll have cracked, warty skins and outer layers.
If nematode symptoms appear, avoid planting onions in the same location for a few years. Starve the population to prevent it from thriving in the garden. Consider control methods if you have severe infestations. Use biological, mechanical, and preventative solutions that target specific nematode species common in your area.
Maggots
Maggots, like nematodes, infect bulbs, stems, and roots. A fly lays eggs near the stem; they hatch into maggot larvae that tunnel into the plants. If their damage doesn’t kill your plants, the rots that follow them will.
You’ll notice wilting, limp onion tops that turn yellow and break easily from the plant. If you pull up the plants and notice holes or signs of tunneling, they most likely have an onion maggot infestation.
Prevent maggots by using row cover to keep the adult flies off your plants. Put them up when they’re active, and take them down when they’re no longer abundant in the area. Remove wild onion and garlic plants to prevent overwintering populations from thriving.
Rot
Rots, like those that follow maggot infestations, are deadly! They cause leaves, roots, and bulbs to turn soft, mushy, and smelly. Fungi, bacteria, and soggy soils can cause weak, curling onion foliage and limp, wilting tops.
One rot, fusarium basal rot, is particularly difficult to manage. Alongside curly, wilting foliage, it causes brown, mushy bulbs. The brown mushiness creeps up into the veggies, causing further damage.
If you notice this rot, avoid planting any species in the onion family in the location for a few years. Plant in rich, well-draining soil, and use disease-resistant varieties for the best results.
