Reading · Your Garden Coach

If you’re serious about growing your own food, you won’t want a garden without onions.

Why?

Because you don’t want a kitchen without onions!

Flavor your soup, your roast, your salad, your sandwich, your pickles, and almost everything else! Many many recipes ask for onions in some way, shape, or form. And there’s a good reason why.

Along with garlic and other alliums, they are the natural garden-grown version of MSG. They take so many dishes to the next level of flavor!

But many gardeners and homesteaders plant onions too late.

In fact, they are the one crop where timing matters more than any other crop.

Let me explain…

Most crops have a clear days to maturity (DTM). This is the approximate number of days it takes them to mature from seeding or transplanting time to harvest time. (It varies, of course, by the weather, the hours of daylight, and the soil conditions.)

Onions also typically have a listed DTM, but it’s not as accurate as other crops.

If you’ve grown onions, you know they initially grow leaves, and eventually transition to forming a bulb.

Here’s how that works…

Onions are sensitive to day length. When the number of hours of sunlight per day reaches a certain threshold, they are triggered to start forming a bulb instead of additional leaves.

And here’s the kicker…

The size of the bulb corresponds directly to the number of leaves on that onion. In fact, every onion leaf corresponds to one ring on the onion. (Seriously, pull out a plant and check it out sometime!)

What this means is that no matter how large your onion top is, the plant will start bulbing at a set time of year. And the larger your top is at that time, the larger your onion bulb will be.

(*This, by the way, is why it’s important to not give onion seedlings too much artificial light so as not to trigger early bulb formation!)

And this is why planting your onions early matters. Earlier planting translates to more leaf growth by the time daylength triggers bulb formation, and this translates to a larger bulb.

Onions are quite cold hardy, and when sets are buried in the ground or young plants are well established, they’ll easily survive a freeze in the field. In severe freezes, the tops may die back slightly, but a strong established root system will quickly push energy back up to form leaves. If your plants are very tiny, as in significantly smaller than pencil thickness, you’ll likely still want to cover them during freezes.

But let’s talk more about daylength…

If you’ve ever purchased onions, you’ve seen the categories: Long-day, Intermediate-day, Short-day. What exactly does this mean? And why does it matter?

These labels are simply a designation for how many hours of daylight that particular cultivar of onion needs in order to form bulbs. And if you understand how your latitude corresponds to your summer daylight hours, you’re already making the connection that northern gardeners will need long-day onions and southern gardeners will need short-day onions.

Here are the types:

Long-day: Trigger bulb formation at 14-16 hours of sunlight, best for latitudes 37-47°
Intermediate-day: Trigger bulb formation at 12-14 hours of daylight, best for latitudes 32-42°. (These are sometimes called Day-neutral, and tend to be more adaptable to a variety of latitudes.)
Short-day: Trigger bulb formation at 10-12 hours of daylight, best for latitudes 25-35°

*Click here for a US map and more detailed description of onion types and which type you should have for your region.

In my region in central Pennsylvania, I normally plant long-day or intermediate-day onions for best results, and I like to plant my onions by the beginning of April.

In ideal conditions and with early enough planting, an onion plant will have a dozen or more leaves by the time bulb formation begins. This should give you a nice, large onion with enough rings to form wrappers on the outside that help your onion store well.

A few more notes about onions:

The love fertility! Onions use a lot of nitrogen in their early stages of leaf growth, and then a lot of potassium and consistent water in their final weeks of bulb formation. *Check out my Garden Resources Library for my favorite nitrogen and potassium fertilizers.
They hate weeds! Among all crops, onions are one of the most sensitive to weed pressure, possibly due to their shallow root system. Keep them weed free and they’ll be much happier! I like to use a stirrup hoe or collinear hoe to shallowly cultivate around the plants. *Check out my Garden Resources Library for more details on these hoes.
If you don’t start your own onions, you can purchase plants online. I often buy from a local seed store or from Dixondale Farms.
In my area, onions are susceptible to a pest called the Allium Leaf Miner. I’ve found several options for dealing with this pest:
- Covering with row cover until early to mid May. This has the added benefit of encouraging more early leaf growth, but it has not been fool proof for solving the leaf miner problem for me.
- Experimenting with later planting to avoid the leaf miner’s life cycle. (Yeah, this goes against what I said in this post!) I tried a late April planting last year and the plants were certainly healthier, and the bulbs were still a satisfactory size.
- Applying a molasses and boron fertilizer. This has worked great in helping my damaged plants recover in the past! See my Garden Resources Library for an exact recipe.

👉 What tips and tricks do you have for growing onions? Comment below and let me know!

Why planting onions early matters

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