How many Onions Grow from One Bulb? | Tips for Growing Onions

Onions are hardy plants with high yields and are an essential part of countless recipes. Because of this, they make for a great crop to grow in the garden. Therefore, it is important to know how many onions we can expect when planting them in the garden.

So how many onions can you expect from one onion bulb? Only onion can grow from 1 bulb. After all, the bulb you are planting is just developing into a larger onion. Therefore, you should plant 1 bulb for every onion you wish to harvest.

Although only one onion will come from one bulb, there are some other ways you can get multiple onions from one plant.

Green Onions

Fresh Green onions isolated on white background

First, let’s talk about green onions. Green onions are the green stems that extend above the onion bulb. They are also known as scallions. If we are counting each stem as 1 scallion, you can expect anywhere from 3 to 10 scallions per onion bulb.

If you are trying to grow green onions from an onion bulb, keep in mind that they are harvested long before regular onions are. Green onions can be harvested when they are about 5 inches in height and at least 6 millimeters in diameter (The diameter of a pencil). Ideally, you just want to harvest them before the onion bulb begins to form.

There are also some variants of onion plants that are specifically grown for scallions. These are called Welsh Onions, but they are more commonly known as “Bunching Onions”.  They are very easy to grow as they require only a small amount care and grow in almost any kind of soil. Therefore, they are great for beginner gardeners.

Flowering Onions

 If left in the garden for a long enough time, onions will eventually develop a flower. Onion flowers feature a spherical shaped head made up of about a few hundred little blossoms. Depending on the variety of onion you planted, these flowers can come in pink, violet, and blue but most commonly, white.

Giant violet Onion (Allium Giganteum) flowers blooming

To harvest the seeds from these flowers and plant more onions, it is essential that you harvest them at the right time. The seeds must be collected before the onion flower blooms. Once the flower blooms, it will release all of its seeds onto the ground.

Once you have some onion flowers that haven’t bloomed, simply harvest them by cutting them from the stem. After that, you want to want let the flower dry out. The flower should be bone dry but not shriveled. Once it is dried out you can harvest the onions by rubbing the flower in your hands. The flower will shed its seeds and you can save them for next growing season. Keep in mind that onion seeds have a shelf life of about 1 year.   

Tips for Growing Larger Onions

Although you only get one onion from each bulb you plant, there are some ways to super-size those onions so you can get the most out of each plant. Growing large onions in the garden is a fairly easy process with these simple tips.

Onion Seeds vs. Onion Sets:

Onions are commonly planted in the garden by starting out with onion sets. While growing onions by sets is the more popular way to grow them, starting your onions by seed gives them a better chance of developing into large onions.

Onions are biannual plants. In the first year, they focus on developing its bulb (the onion) as well as a strong root system. In the second year, they focus more energy on developing the flower that will produce the onion seeds for next generation.

Therefore, when you plant onion sets, you are just growing onions that were grown last year and harvested early. Because of this, the onion sets you planted in your garden will be spending less energy on growing the onion bulb, and more energy on developing the flower.

Starting your onions by seed is similar to starting many other vegetables in your garden. However, one notable difference is that onion seeds are started well before most other vegetable seeds are.

Onion seeds should be started indoors 8-10 weeks prior to transplanting them to your outside garden. Sow seeds ¼ inch deep and keep them in a sunny area. Onion seeds will germinate within 4-10 days after sowing.

Selecting Larger Onion Varieties:

Not all onions are made equal. Some onion varieties naturally form larger onions bulbs and some; like the bunching onions discussed earlier, don’t even form bulbs at all. Therefore, it’s essential that you choose the right onion variety if you expect to grow bigger onions. Some large onion varieties include:

Keep in mind that red onion varieties are typically slightly smaller than other onion varieties. The biggest of all the onion varieties however, is the Kelsae Giant. Grown under the right conditions, these are known to be record breaking onions with the potential to grow over 15 pounds!


Of course, we weren’t going to leave out fertilizer as it is essential for nearly all garden crops. But kind of fertilizer is best suited for onions? While fertilizers with potassium and phosphorus are ideal for growing large onions but, nitrogen by far is the most important thing to look for when looking to fertilize onions.

The leaves on the onion plant are what take in many of the nutrients that help the onion grow in size. Every leaf the onion plant produces adds another layer to the onion therefore, making it bigger.

Given that nitrogen is so essential for growing onions, blood meal would be the best kind of fertilizer for growing larger onions. Blood meal is packed with nitrogen and therefore, will allow your onion leaves to grow big and healthy which will in turn, allows your onions to grow big and healthy.

Keep in mind that too much nitrogen however, can be a bad thing. Make sure you follow the product instructions on your blood meal as it contains concentrated amount of nitrogen. Too much nitrogen in your garden soil can kill the plants.

Pruning Your Onions:

When it comes to growing large onions, pruning is essential. It may seem counterintuitive to cut off portions of the plant in order for it to grow larger, but hear me out. Onion plants always need to be growing upwards. If any of the leaves (green onions) begin to wilt or crimp over, it sends a signal to the plant that it is done growing. As a result, the onion itself will stop growing.

Therefore, if you see any onion leaves drooping  or bent over, it is recommended that you prune the leaf by cutting it just below the part where it starts to bend.

One trick to prevent your onions leaves from bending over is to utilize a tomato cage. Simply place the cage over the onion plant and allow leaves of the plant to rest on the inside of the cage. As a result, the leaves will not crimp or bend over and won’t have to prune your onion leaves.

3 thoughts on “How many Onions Grow from One Bulb? | Tips for Growing Onions”

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