Why Are Your Onion Bulbs Not Growing?

Onion sets are easy to grow and are generally ready for harvest in about 2 to 3 months, depending on the variety. They demand little care and are less susceptible to diseases and pests. However, there are still some problems that might bother onion growers. Once you plant onion sets in the soil, you expect to see some green growth within the next few days. It can be heartbreaking not to find any progress even after weeks! 

So the question is – why are your onion bulbs not growing? Let’s explore what might be causing the problem and how to fix it. 

Why Are Onion Bulbs Not Growing – Most Common Reasons

There can be multiple reasons why your onion bulbs refuse to sprout. Let’s see each one in a bit of detail and understand how to avoid and/or solve them. 

You Have Planted Grocery-Store Onions

Probably the most common reason for gardeners that face this problem is that they’re trying their luck with store-bought onions. Onions are an essential staple crop. Plenty of research goes into developing new ways to prolong the shelf-life of harvested onions and prevent them from sprouting in storage. 

Sprouting of grocery store onions diminishes its market value, which is why they are treated or engineered to prevent sprouting.

If you plant these onions in the hopes of producing a crop, chances are you won’t have any luck. 

Instead, among the grocery-store onions you have in your pantry, look for one that has already sprouted. Such an onion, which is already showing signs of green growth, will most likely develop faster once it’s planted in fertile soil. 

Your best bet is to avoid grocery-store onions altogether and shop for onions sets at a local nursery or place an order at one of the online retailers. Unlike grocery-store onions, these onion sets are bred to be planted in gardens and will produce the best results. 

Incorrect Planting Time

Onions, like most other crops, go dormant during the winter months. If your onion sets are not sprouting, you may have planted them too early. Planting at the right time and not too early is especially important in the northern hemisphere because the light levels are too low, and the soil is still cold before March or April to trigger any green growth. 

If you’ve planted the sets too early, leave the bulbs in place and wait for the warm weather to set in. there are chances that the bulbs will sprout in time, and you’ll see shoots appearing as soon as the weather is favorable for them. 

Alternatively, plant some more onion sets at the correct planting time for your region. For a spring planting, set the sets in the garden as soon as the soil can be worked in spring, which is usually around March or April for most regions. The outdoor temperature should be consistently above 28°F after the onion sets are in the ground. 

Incorrect Planting Depth

Planting them too deep into the soil or too shallow can be another reason for delaying (or halting development). Plant the onion sets just enough to cover the tips with 1 inch of light, friable soil layer, and no more than that. A thick layer of soil over your onion sets will not only delay sprouting but will also diminish the development of bulbs, especially if you have clayey soil in your garden. 

Incorrect Onion Variety For Your Climate

Not all onion varieties will necessarily thrive or even grow in your region. Your climate governs the type of onions you can grow in your garden, so make sure you select a variety that’s suitable for your growing zone. 

If you try to grow an onion variety that’s not compatible with your region, it’s very likely that you’ll get a smaller harvest. Many of the onion sets won’t even sprout since they won’t find the favorable temperatures or humidity levels that trigger their growth. 

Make sure you know your growing zone. Read the specifications for the onion sets and establish that the variety is correct for your region before you plant it in your garden. 

Onion Fly Maggots

Onion fly maggots may often be the mischievous culprits behind onion bulbs not growing. If you have yellow, drooping leaves, or if onions aren’t sprouting right from the start, it’s very likely that onion fly maggots have found their way to your garden. These are destructive pests and attack onions by laying eggs at the base of the crop. The eggs hatch into maggots which feed on the onion roots to stop growth. If they attack the crop early, onion fly maggots will kill the onion sets before you even see any sprouting. 

To establish for sure if it’s really onion fly maggots that are causing the problem, just lift a bulb from the soil and look for tiny maggots clinging to the roots or moving about in the soil where you lifted the bulb from. 

Unfortunately, once onion fly maggots attack your crop, there are no effective chemical treatments to eliminate them and save the bulbs. However, you can prevent them from attacking in the first place by placing row covers on the crops at the time of planting. Additionally, rotate your onion crops to prevent the problem from persisting in your future onion crops.