Are you worried about your onions with leaves that are falling over and drooping? If so, you are probably wondering why your onion leaves are laying down on the job.
So, why are your onions falling over? Onion leaves fall over when the plant is mature and the bulb is ready for harvest. This happens after the leaves have sent their energy to the bulb to make it grow bigger. Lack of water, pests, and diseases could also cause onion leaves to fall over.
Of course, different varieties of onions will mature at different times. As a result, your onion leaves might fall over sooner than your neighbor’s if you are growing different types of onions.
In this article, we’ll look at why onions fall over, when it happens in mature onions, and what to do if there is a problem.
Let’s get going.
Why Are Your Onions Falling Over?
Often, the leaves on your onions will fall over simply because the plant is mature. However, there are other reasons it can happen, including:
- Shallow planting at transplant
- Lack of water
If it is late in the season, maturity of the onion bulb is the most likely reason that the leaves are falling over. Let’s begin there.
Sometimes, when your onions fall over, it is a sign of maturity. In that case, it is no cause for concern.
After planting onion seeds or sets, leaves will eventually appear. Given enough time, onion leaves will grow taller and start to produce energy by photosynthesis.
The leaves then send their energy (carbohydrates or sugar) to the layers (scales or rings) of the onion to make the onion “bulb up” (get larger). A “perfect” onion has 13 layers and 13 leaves – one leaf for each layer.
Once the onion bulbing process begins, no more leaves are made. So, you want the plant to produce all 13 leaves before bulbing to get the largest onions possible.
When Do Onions Start to Bulb?
Onions start to bulb once the days become long enough in summer. According to the North Carolina State University Cooperative Extension:
“Onions form bulbs in response to day-length. When the number of daylight hours reaches a certain level, onion plants start bulbing, or forming bulbs.”https://burke.ces.ncsu.edu/2016/11/the-secret-to-growing-great-onions/
Of course, the hours of daylight required for bulbs to form will vary depending on the type of onion. There are 3 basic types of onions:
- Short day – these onions need 10 hours of daylight to produce bulbs. They do best in Zones 7 and warmer (southern United States).
- Long day – these onions need 14 to 15 hours of daylight to produce bulbs. They do best in Zone 6 and colder (northern United States). If the day length does not get long enough for long day onions, you will get green leaves with no bulbs at all!
- Day neutral (intermediate day) – these onions produce bulbs regardless of day length, and produce bulbs anywhere. They do best in Zones 5 and 6, and should be planted in early spring (northern regions) or in fall (southern regions).
So, if you plant your onions too late, they won’t get a chance to produce the 13 leaves necessary for a “perfect” onion. The leaves that are produced will not produce as much energy, and you will get smaller bulbs as a result.
However, if you plant too early, you expose your onions to the risk of late spring frost. One good solution is to start your own onion seeds indoors and transplant them to the garden later.
According to the University of Minnesota Extension, you should start onion seeds indoors about 10 to 12 weeks before transplanting into the garden. Transplant when temperatures reach 50 degrees Fahrenheit (10 degrees Celsius).
To grow the biggest onions possible, be sure to get the right variety (based on day length) for your area. The seed package or website you buy from will indicate the type of onion (short-day, long-day, or day-neutral), along with the days to maturity (time until you get an onion bulb).
When Do Onion Leaves Fall Over?
Onion leaves fall over when they get too heavy and cannot hold themselves up. In mature onions, this means the end of the growing season, since the bulbs will not get any larger after this point.
At that point, the onion leaves have already sent their energy to the bulb to make it bigger. They start to turn yellow, shrivel up, wilt, and droop because they have given everything they have to the bulb.
When onion leaves fall over, the bulb is done growing. At that point, it is time to harvest and cure the onions.
There is no reason to bend or knock over the leaves of onions. They will fall over by themselves when they are ready!
In fact, bending the onion leaves before they are ready may be detrimental to bulb formation. According to the Texas A&M University Extension:
“Onion bulbs increase in size as sugars manufactured in the top are translocated to the bulb. If the tops are broken, this process stops, preventing further bulb enlargement.”https://aggie-horticulture.tamu.edu/archives/parsons/vegetables/onion.html
When to Harvest Onions
When the leaves turn yellow and start to fall over, it’s time to harvest your onion bulbs. By this time, the bulbs should also develop outer scales that are like paper (the noisy part we peel off before chopping up onions for cooking).
Before putting onions away for storage, be sure to cure them! According to the Texas A&M University Extension:
“Maturity is indicated by the fall of the top of the onion plant. After the tops have fallen, pull and dry the onions in the garden for several days. Some gardeners prefer to pull the onions up partially which allows the onions to dry while still in the ground. After drying, remove the roots and the top, leaving about 3/4 to 1 inch of the neck to seal and prevent entrance of decay organisms.”https://aggie-horticulture.tamu.edu/archives/parsons/vegetables/onion.html
Remember that onions will sprout if kept above 40 degrees Fahrenheit (4 degrees Celsius). Do not freeze onions (below 32 degrees Fahrenheit or 0 degrees Celsius).
According to South Dakota State University, if your onions “bolt” (send up stalks with flowers and seeds), harvest them right away. Use these bolted onions first, since they won’t store as long as onions that have not bolted.
If you find that any of your stored onions sprout, you can plant them and let them grow anew! You can learn more about planting sprouted onions in my article here.
Shallow Planting at Transplant
Are your onions falling over long before maturity? If so, then one possibility is that they were planted too shallow at transplant.
According to the Texas A&M University Extension, onion transplants should be planted at least 1 inch (2.5 centimeters) deep. This leaves enough soil to anchor the plant and keep it from falling over.
Lack of Water
Dry conditions will cause early bulbing in onions. Once the bulb starts to form, leaf growth will stop, and the leaves will fall over.
“Onions are shallow rooted. If allowed to dry out, they bulb early and small size is the result.”https://today.oregonstate.edu/news/no-need-tears-if-you-plant-onions-soon
Onions need lots of water early in the season. Water onions often, and even more so if your soil is sandy.
Using a thin layer of mulch helps to retain moisture in the soil by preventing evaporation. You can learn more about mulching around onions in my article here.
Towards the end of the growing season, reduce the water to your onions. For a good indication of when to do this, wait until the leaves stop forming and begin to dry out.
There are some pests that feed on raw onions, as unappealing as it may seem to us. One such pest is the onion maggot.
Onion maggots bore into the stems of onion plants. Their feeding will cause the leaves of onions to turn yellow and wilt.
According to the University of Vermont, you can prevent onion maggots by using row covers. Put them over your onions for the first few weeks of the season to discourage flies from laying their eggs on your plants.
There are several diseases that can affect onions to give their leaves a wilted or drooping appearance. One such disease is downy mildew.
According to Wikipedia, downy mildew is caused by fungus-like microbes that are parasites to plants. Downy mildew causes yellow areas on the leaves of plants, including onions and others such as crucifers (broccoli, etc.)
Downy mildew is more common in the southern United States, since it cannot survive the cold northern winters.
Your best bet for avoiding disease in your onions is to choose disease resistant varieties. Print and online seed catalogs will indicate disease resistance in the description.
Now you know why your onion leaves are falling over and when to expect this in mature onions. You also know how to deal with other common problems that can cause onions to fall over.
If you are looking for heat tolerant onion varieties, you can find some in my article here.
I hope you found this article helpful. If so, please share it with someone who can use the information.