How To Grow Hydroponic Onions with 5 Simple Guidance

Hydroponic is not merely about leafy green crops, but it can be hydroponic onions too. Yes, it is possible to grow a root plant like an onion using a hydroponic system.

root plant like an onion
Source : / Yard

There may be less information that you find about it. Thus, the following article will share with you a valuable experience about how to grow onion in a hydroponic system.

Seeding the Hydroponic Onions

Seeding the Hydroponic Onions
Source : / AGRI MECH

There are some types of onions varieties, and to get better crops, you should select the best one. For a hydroponic method, you can choose short-day onion varieties.

What is a short-day onion? This variety changes the leaves into the bulbing growth phase when it receives lights from 10 to 12 hours daily. It is favorable for an area with a cooler temperature.

As onions the warm weather plant, it will require a lot of lighting and heating for a hydroponic. So, to avoid the high cost of electricity, you are recommended to choose short-day onions for your hydroponic onions.

This variety requires less daylight in its growing phase. You will need around 10 to 12 hours of growing light every day. You can compare this with a long-day onion that requires 16 hours of lighting.

You can grow the onion directly from the seeds or the bulbs first. Some growers prefer to start from the bulb. They place it in a growing medium then, remove the sprout to the hydroponic set.

You must wait until the sprout stable before you place it in the hydroponic set. So, your crops will adjust easily in the hydroponic set.

Hydroponic Onions Nutrient Solution

Hydroponic Onions Nutrient
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Although the hydroponic system requires nutrients in its reservoir, it does not merely work for your onion. In the earlier stage, it is better not to give any nutrients to the water.

Let the seedling onion starving to make them form the root. This process allows the starving onion to search for nutrients. Then, you will get its root longer and stronger.

After you place them in the hydroponic set, you can supply them with the nutrient. Once you include the nutrients into the hydroponic set, they will form a more stable root. It will absorb nutrients to optimize growth.

You should do extra caring for your onion. Make sure to have a balanced nutrient solution. If you give too many nutrients, it will create unnecessary foliage and can sacrifice the onion bulb.

Meanwhile, less nitrogen will make your crops lose their growth and stamina. Before you give the nutrients, follow the direction mentioned in the package.

The nutrients quantity should be balanced with the pH levels and electrical conductivity. You have to check the pH level that is from 6.0 to 6.7 to have a proper nutrient solution. Besides, you have to change the nutrient every three weeks.

Temperature and Air Flow

Temperature Hydroponic Onions
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Growing hydroponic onions can be indoors or outdoors. You can decide which one are suitable for your need. So, you know where to place your hydroponic set.

Onions are easy to cultivate in the hydroponic system. If you are a beginner grower, you don’t need to worry. Starting them would not cause you a complex problem.

Onions grow at a temperature range between 65 to 70 degrees Fahrenheit. Allowing the crops in this temperature can support the growth and maintain the plants to grow healthier. If the onions grow outside those temperature ranges, they will not perform the maximum growing effort.

Besides, you should care about the presence of pests too. You must be able to protect them from bugs that may endanger their life.

Another thing you should consider in growing onion by a hydroponic method is air circulation. Onions grow with high levels of moisture. It can attract bacteria or mildew growths if your hydroponic system does not have proper air circulation around.

For an indoor garden, you are recommended to install fans to support good circulation. You can place them in the exhaust, floor, or ceiling. Make sure that it has better ventilation.

Light Supply

Light Supply onions
Source : / SlivkiShow EN

In the conventional method or the soil-attached growth, the best lighting for your onions is at full sun. You should place your plants with enough light to stimulate better growth.

As mentioned above, the recommended variety for growing onion in the hydroponic system is a short-day onion. The reason is this variety requires light lesser than any other varieties.

Generally, indoors hydroponic systems need approximately 12 hours of light daily. It can be less for a short-day variety.

The average light for this variety is 10 to 12 hours daily. If you plan to have a growing lighting installment, it is better to use LED grow lights for electric power efficiency.

The light supply for onion differs from one variety to another. The shortest one is as mentioned in the preceding paragraph. Meanwhile, other varieties such as long-day onion may need light supply up to 16 hours per day.

You can also make arrangements for your indoor hydroponic garden without any lighting installment. You must be sure that your crops get sufficient sunlight at all times. Otherwise, all of your efforts will be useless as the plants may be decay without proper light.

The Best System for Hydroponic Onions

The Best System for Hydroponic Onions
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Taking a hydroponic system for your onions can be tough. The reason is that onions are root crops. So, they are different from other leafy crops.

There are three systems that you can apply for your hydroponic onions. This system can also be applied to other root crops.

The first is the Nutrient Film Technique. This system allows growers to have high productions due to it requires less space. Unfortunately, it becomes their weakness too.

Spacing is essential for growing your onions. If you plan to apply this system, you must pay attention to their spacing. By providing the right spacing to each onion, you can lessen their effort in searching for light especially in the harvest time.

The second is Deep Water Culture or DWC system. This hydroponic system can be suitable for growing your onion. It can be an excellent choice, especially for a beginner.

However, you will not produce high quantities of onions due to its limited space available. You can maintain your crops easily using this system.

The third is The Kratky Method. This system has been applied for a long time. You place the half-grown onions into jars filled with water and leave them beside the window.

Can Onions Grow Hydroponically?

onions grow hydroponically
Source : / Garden Ideas

If you plan to grow the onion in your garden, don’t be doubt to choose the method. You can apply the hydroponic system for better selections.

You can cultivate your onion easily by applying the hydroponic method. Moreover, it is a simple method for a beginner too, because you will have less problem in growing them.

The process of it is also simple and not complicated. What you need is a jar filled with water and an onion bulb. Furthermore, it will require less time to consume too.

For planning a bigger hydroponic farm, you will need more tools and equipment. However, you don’t need to worry because it will not be complicated as growing other crops.

The maintenance is also easy. You don’t require a mountainous task for proper maintenance. By paying attention to its caring method, you have a successful hydroponic garden for your onions.

How Long does It Take to Grow Onions Hydroponically?

onions hydroponically
Source : / on Growin’ with Mike VanDuzee

Now, it is the harvesting time for your onions. There is some following information you should know before you harvest them.

Harvesting the hydroponic onions are quite similar to harvesting the conventional method. There is the same guidance for their rooting that you must know.

If you start your onions from seeds, the harvesting will happen around the third or four months after you plant them. Meanwhile, if you begin with the small bulbs, you can expect the harvesting time within 80 to 90 days.

When you find out the foliage yellows and falls, you should soon harvest them. That means your onions are in their last ripening stage.

If you have proper care of your onions, you can harvest them at the right time. Make sure you prune them regularly to have bigger and well productive crops. By growing a healthy onion, you can get fresh and tasty onions during the harvesting time.

How do You Grow Onions in the Water?

grow onions in the water
Source : / Gardening

As mentioned earlier, onions are easy to plant growth in the water. You can have them without nutrients in the early growing stage.

However, there is crucial information that you must know in this method of growing. It is about the water that you use to plant the onions.

You must use water that free of chlorine. This chlorinated water is totally not recommended for your hydroponic crops.

Yet, if you have no options, you can use it as long as the chlorine is removed. There is a simple method on how to remove chlorine from the water.

You can allow the water to sit approximately for an hour or so. After that, you can check the water and see that the chlorine dissipates. You will find the chlorine is floating in your sitting water.

Set aside the chlorine and take only the below water. By using this water, you can grow your hydroponic onions well.

Related: How to store chives long term in fridge  


In conclusion, hydroponics onions have been around since the 1960s, when the first research paper was published on the subject. At that point, scientists were working with tomato plants and applying the same principles to other vegetables.

By the early 2000s, more than 200 million square feet of greenhouse space were devoted to growing food. According to the International Society for Horticultural Science, worldwide, about 90% of fresh produce comes from greenhouse-grown crops.