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How to Get Onions to Flower

A collage photo of picturesque and attractive onion flower.

Onions are a biennial plant, and this means that their full flowering cycle is two years long. Their growth cycle goes from seed, to plant, to bulb over two years. You will see onions have a top growth by the end of the first year and then flower in the second year until the plant will go to seed.

Some gardeners typically do not want their onions to go to flower, but there are advantages to it as well. You can also create the optimum conditions for onions to flower, where they can be a beautiful, and even tasty, treat. Learn more about how to get onions to flower here.

Flowering and Onions

Bees on blooming garlic in the garden.

When onions flower, a flower has emerged from the stalk much like any flower does. Patience is important for the gardener working on this as an onion is not likely to flower in its first year. If there are extreme climate changes with temperature fluctuations then an onion plant may flower in its first year.

The plant stalk grows, a bud forms, and the bud becomes a blossom, while the plant bulb is working on creating an onion. That blossom, like most flowering plants, produces more seeds that can become new life for the plant. That life cycle takes up to two years, which is what makes onions a biennial plant.

This is the case with most onion varieties. However, there are some onion varieties that are perennials that do not flower. Although most onions will have a two-year life cycle, most gardeners will harvest onions within the first year before they go to seed again in the second year.

In this case, the bulbs of the onions will be pulled for harvest. A perennial onion on the other hand will be able to stay in the garden for years. This onion can multiply on its own and grow to the harvest.

These onions can also be enjoyed year round, as perennial onions are hardy plants that can withstand the cold when they are maintained properly. The process of an onion going to flower is called onion bolting. If you want your onions to go to flower, there are certain conditions under which that can happen.

Factors In Onion Bolting

Close-up of an onion bolting.

Onion bolting happens when an onion flowers. This can happen as part of the normal life cycle of a plant, or it can happen when the plant has matured too soon. There are a number of different factors that can contribute to onion bolting.

The key reason that an onion will bolt or flower is that it has reached its maturity. In this case, the onion has made its bulb and is shooting up its seed cycle. Here you will see an onion flower.

This happens in the normal life cycle and will occur right before the plant goes dormant. An onion can bolt or flower if it is exposed to weather that is too cold as well. Onions can be hardy plants in the winter, but will also need to be well maintained in order to survive.

If they go more than a few weeks in weather that is below 50 degrees, they will not survive. Sudden weather changes from cold or cool to extreme hot will also cause onion bolting. The conditions around the onion matter as well.

If the onion is too dry or if it gets too wet, this can result in onion bolting. When an onion is bolting, it is telling you that it is at the end of its life cycle. Instead of focusing on a harvest or bulb, a bolting onion is saying that it is getting ready to seed.

As a result, it is putting all of its energy into creating seeds. You can not reverse the stage of a flowering onion. You can leave the onion to grow as is and seed on its own timing. 

You can also simply bend the onion stalk and remove the onion flowers. Some gardeners will remove all of the tops of onions before they harvest. You can still eat an onion that has begun bolting, and this will become green onions to eat.

It is unlikely that you will get a bulb from a flowering onion. If you do, the bulb quality is going to be low. That is because the plant is using all of its energy for the plant and that is going into the flowering stage.

You can encourage an onion to flower by managing the climate it is in. During extreme cold temperatures, leave the onions uncovered and force them to go into their dormancy cycle. Extreme changes to the weather in the way of heat will also encourage bolting.

Decrease your watering for onions that you want to bolt. When the soil is very loose and moist, an onion will continue on its normal cycle. When the soil becomes almost baked or brittle, the onion is going to feel forced to bolt and go to seed because it won’t have the climate it needs to put its energy into expanding the bulb.

 After you have grown onions for a few years, you will become accustomed to this life cycle and get used to encouraging their growth and flowering process. It just takes practice, but once you get an onion to bolt on your own, it is a very exciting and beautiful accomplishment. Ensuring the onions have been planted and maintained properly will be key in helping you get the onion to flower.

Necessary Conditions for Flowering Onions

Decorative onion grows and blooms on a flower bed in the garden.

Like every plant, onions need conditions under which to grow, and every gardener can optimize those. When an onion is growing under the right conditions, you can help it get to its bolting or flowering point. A good soil is critical to any plant’s normal life cycle, and an onion is no different.

Start with a very loose soil that the onion can survive in, and grow healthy bulbs in. You may not want onion bulbs to eat, but may just want the onion to become flowers. Still, you want a nitrogen rich soil for the plant that will help it to grow.

A good compost for the onion plants will help as well. As the onions are growing in their first year, fertilizer can feed them well. This will help them to reach their green cycle.

When an onion is growing as a green onion, you can get it to flower. If you are fertilizing onions, you want to do so before the weather becomes warmer. For the best onions, you want to keep them moist and watered enough so that they don’t become too dry.

A consistent watering is enough if you want the onions to flower. Well drained onions will become bulbs, but if you water too much after the first year, you may not get the onion to flower. Bulbs of onions are rich in moisture.

When they get the moisture they need, they begin to use their energy resources to push into big bulbs. Less is more when it comes to watering onions if you want them to become flowers. Water them just enough.

This will also help you to control root rot and disease in onions. Overwatering can be a problem for any plant, and an onion may avoid the flowering stage and send all of its moisture to the bulb if you are watering too much. If the soil that you are touching is just moist enough, you have fed the onion plant enough water to continue on its normal life cycle.

Weeding onion plants is as important to them when you want them to flower, as it is when you want them to push the bulb out for harvest. You will need to keep the onion plants well controlled when it comes to weeding. Watch your onions for weeds as early as you plant them.

Mulching the surface of your onion plants can help you here. It is worth noting that when an onion goes to flower, that does not mean that you will lose the bulb for harvesting. You can still harvest a bulb after the plant has gone to the flowering stage.

The onion bulb will not be as good or robust as it would be, as much of the plant’s energy has gone to the flower to create seeds for more plants. However, you can still have the best of both worlds here. You can harvest some onion plants early, and leave some in the ground until the next year.

With the plants that you have left in the ground, you will get flowering onion plants in the next season. Leave them over winter and you can watch this miracle for yourself. Onion flowers can be quite beautiful and are worth the wait.

Frequently Asked Questions (FAQ) About Onion Flowering

Q: Can you use onion flowers after they have gone to seed?

A: Many gardeners that want onions to flower want this to happen for a few reasons. Some just want to see the beauty of the onion flower, while others want to use the flowers to go to seed to create more onion plants. Once the onion has gone to flower, you can use those for many things.

You can use them to create seedlings and start new onion plants. You can also use them to eat, as the flowers will still produce a fragrant and tasty onion flavor to some dishes. Onion blossoms are frequently used with oil or vinegar infusions in dishes, and this also makes a lovely bottled oil you can use for display or eating purposes.

You will find the taste of the flowers almost the same, but slightly milder than harvested onion bulbs.

Q: What are long day and short day onions, and does this impact flowering?

A: The difference between long day and short day onions is the amount of time of sunlight required for them to reach their optimum conditions. A short day onion requires less sunlight than a long day onion. Short day onions need between 10 and 12 hours of sun for a good bulb or flower.

A long day onion needs between 14 and 16 hours of sunlight in order for a good harvest. There are some gardeners that will talk about intermediate day onions that can handle between 12 and 14 hours of sunlight, but the most common are long day and short day onions. If an onion is biennial, it will flower if you want it to.

It does not matter if it is a long day or a short day onion.

Q: Is it better to grow onions from seeds or from sets?

A: Some gardeners will say this is a personal preference, but that onions from sets are most likely to flower the way that you want them to. Onions in sets will mature earlier and can withstand temperature changes a little easier. They are going to do better than a transplant will.

You also won’t need the patience here as much as you will with onions from seeds.