Seeing your onion tops falling over early is alarming. Later in the season, it’s perfectly normal for onion tops to fall over. But when your onion tops fall over early, then something is wrong.
Onion Tops Falling Over Early: 5 Possible Reasons
- Wind damage
- Damping off
- Stem and bulb eelworm
- Allium leaf miner
- Purple blotch
1. Onion Tops Falling Over Early Because Of Wind Damage
Have you had any strong wind lately? If so, wind damage is the likely culprit behind your onion tops falling over early.
There’s good news though.
As long as the onion leaves are still green, your onions should carry on growing.
They’re a little battered, and you won’t get the biggest onions this year, but you’ll still get a harvest.
Wind damage usually occurs when onions have some fairly good top growth, so wind is unlikely to be the reason younger onions have fallen over.
How can you prevent wind damage in the future?
Always try to plant your onions in a sheltered spot where the wind can’t get at them.
Of course, all vegetables benefit from shelter, and it’s not always possible to plant everything you grow in a spot where your home, shed, fence or garden walls offer protection from the wind.
Here at the homestead we build small windbreaks around planting beds using willow stakes and bracken, since both are in plentiful supply on the land. These rough and ready fences help to stop incursions from wandering chickens, too.
If we didn’t have access to those materials, then hunting down some unwanted pallets would be high on my to-do list.
Pallets make great, free wind breaks, and they’re not too unsightly if you spruce them up with some fence preservative.
For an endless supply of pallet fence ideas head over to Pinterest and search for pallet fences. You’ll be amazed at the clever ideas.
2. Onions Tops Falling Over Early Because Of Damping Off
Damping off is a condition which can strike young onions when they’re still at the seedling stage, as well as more mature onions.
The problem is caused by common soil-borne fungi species:
- Pythium
- Rhizoctonia
- Fusarium
- Phytophthora
Once damping off becomes noticeable, there isn’t anything you can do to save onion seedlings.
If damping off is the cause of your onion seedling tops falling over the lower stems will be dark brown or black and the seedlings will eventually fall over.
In older onions, damping off causes stunted growth, yellowing of leaves, and wilting.
Damping off in seedlings can be prevented by helping seeds to germinate quickly, and by making sure the starting mix or compost isn’t too wet. For faster seed germination, use a heat mat.
3. Onion Stem And Bulb Nematode Attack
This pest is a microscopic worm which causes onion leaf and bulb distortion. The leaves of affected onions will often swell, twist, fall over and lie against the ground.
Stem and bulb nematodes (Ditylenchus dipsaci) are also known as stem and bulb eelworms and onion eelworms.
These little pests were already living in your soil or they were present in the onion sets or transplants you purchased.
Onion eelworms multiply when weather conditions are cold and wet in the spring, and when this problem is the reason your onion tops have fallen over early, there’s nothing you can do to save the crop.
You can see images of onions with stem and bulb nematode damage here and here.
When young onions are infected, the parasite tends to kill the plant. In older plants, the onions become soft and tend to rot.
Remove the infected crop and bag it for disposal or burn it. Don’t put the onions on your compost heap.
Avoid planting onions, garlic, shallots, carrots, beans, beets, leeks, chives, celery, parsnips, tomatoes, cucumbers, or strawberries other susceptible crops in the growing bed for 3 years.
That rules out a lot of your planting options, I know, but you can grow lettuce in the bed, and after 3 years, the nematode problem should be gone, because the parasites can’t breed in a non-host plant like lettuce.
Three years is a long time to wait though, especially if you’ve got limited space, and no interest in growing lettuce for 3 years. So what can you do?
For a faster solution that allows you to plant a fall crop, or get your growing bed back into production the following spring, try soil solarization.
This nematode eradication method takes place over 6 to 8 weeks in the summer, and as a bonus, soil solarization will also kill off weed seeds.
Soil solarization works by trapping the sun’s heat under a clear polyethylene sheet. Think of how hot a greenhouse gets in summer. That’s how hot your soil will get.
The heat “sterilizes” the soil to a depth of around 8 inches, wiping out the nematodes.
Dig over the area first, and make sure the soil is loose with no big lumps.
Next, water the soil so it’s moist. Hot, humid conditions are more effective at killing the nematodes than hot, dry conditions.
Then, lay the clear plastic sheet over the affected area, and weigh it down with some rocks or water filled milk jugs so it doesn’t blow away in the wind.
Let the sun do its work for a few weeks, and you should be all set.
4. Allium Leaf Miner Damage
The allium leaf miner (Phytomyza gymnostoma) is a tiny fly that lays eggs on onions, garlic, leeks, shallots, and chives. When the eggs develop into larvae, the maggots burrow into the onion leaves, stems, and bulbs.
Leaf miner damage causes leaf distortion and some onion leaves will fall over, growing against the ground instead of upright.
Look closely at your onions and you’ll see small pale green or gray marks running in lines along the leaf.
These marks are evidence of the adult fly feeding on the onion leaf sap before she deposited her eggs.
Remove the leaves and you’ll find tiny cream or brown maggots wriggling around on top of the onion bulb.
You can still use the onions if you’re quick, but they won’t store well because the leaf miner damage provides an entry point for bacteria which causes the onion to rot.
Remove all infected plant material and dispose of it or burn it. Leaf miner larvae will overwinter in soil and complete their life cycle the following spring when they mature into leaf miner flies.
To prevent leaf miner attacks next season, rotate your onions into a new bed and use a fine net row cover over your growing beds to keep the flies off your plants.
5. Purple Blotch
While there’s a possibility that purple blotch could be the reason your onion tops are falling over, it’s not very likely unless you’re also seeing large oval lesions on your leaves.
Purple blotch is caused by the Alternaria porri fungus, which causes leaves to wilt 2 to 4 weeks after infection.
This fungus thrives in the warm, moist weather conditions common in some areas after mid-season.
Again, there’s nothing you can do to rescue the crop once the leaves have fallen over, and you’ll need to bag up the onions for disposal or burn them.
Avoid planting onions, or other alliums in the bed. unless you use the soil solarization method mentioned above.
Final Thoughts On Onion Tops Falling Over Early
I wish I had better news for you in this post, but the sad truth is once these infections and insect attacks damage your onions, there really isn’t anything you can do except chalk this up to experience.
Make sure you grow onions in a new bed next year (always rotate your crops) and if you’ve still got plenty of hot summer days ahead, pick up a large sheet of UV resistant plastic so you can solarize your soil.
Thanks for reading: Onion tops falling over early. I hope this helps you figure out what happened to your onions.
