Hydroponic Onion Farming - Growing Guide

Hydroponic Onion Farming

Growing your vegetables in hydroponics is incredibly rewarding. Not only will hydroponics provide you with the vegetables you love to eat, but it can also help you save money and improve overall health. Growing hydroponic Onions is not only tasty and nutritious, but they’re also the easiest hydroponic vegetables to grow. Hydroponics is a method of cultivation that does not require the use of soil. Instead, you’ll rely on nutrient water or moist air to cultivate your hydroponic plants. Some root crops like Onions can be grown hydroponically with simple and easy steps just like leafy greens. Though, there are some key factors that you have to consider to get the largest Onion bulbs possible. The most important part is maintaining the hydroponic Onion conditions to keep the growth rate maximized as much as possible. In this article we also covered the below topics about hydroponic Onion farming;

Simple process to grow hydroponic Onions
Can you grow Onions hydroponically?
How long does it take to grow hydroponic Onions
How to grow hydroponic Onions
What is the best hydroponic system for growing Onions
What do you need to grow Onions hydroponically

A Step-by-Step Process to Hydroponic Onion Farming

Hydroponic cultivation of Onions has gained the greatest popularity. Onions are known for being relatively easy to grow plants hydroponically, needing only a jar of water and a windowsill with adequate sunlight. Within a week, Onions will begin to grow green sprouts, which can be harvested continuously and used in a different variety of dishes and recipes.

Best Onion Varieties for Hydroponics System

You have to choose the right Onion variety for the hydroponics system. There are mainly three groups that determine Onion varieties;

Short-day Onions
Intermediate Onions
Long-day Onions

Short-day Onion varieties are the most suitable Onion variety to grow using any hydroponic system. If you are planning on growing Onions using a hydroponics system, then you are probably going to use grow lights and heating systems as well. Appliances like this tend to consume too much electricity that might cost you a fortune at the end of the month, particularly when you are trying to grow a large volume of Onions.

Short-day Onions need less daylight time to transfer from the vegetative stage to the bulbing stage. So, instead of growing long-day Onions and having the need to keep the growing lights running for 16 hours every day, you will only open them from 10 to 12 hours. Another benefit of growing a short-day variety in hydroponics is their ability to tolerate cold. This Onion variety is originally grown in the southern regions where temperatures are low. Short-day Onion varieties are a huge money saver that will still grow large despite the shorter light time.

The short-day varieties for hydroponics that you should choose from are;

Texas Super Sweet
Yellow Garnex
White Garnex
Texas Sweet White
Sweet Red
Georgia Sweet
White Bermuda

Building Your System for Hydroponic Onions

You can buy a system online or also you can build one yourself. Building a hydroponics system can be somewhat complicated, but you want to save some money and are relatively handy.

If you decide to do this, you’ll need the following equipment;

Grow tray and stand
An air stone and air pump for oxygenating the nutrient solution
A resource to hold the nutrient solution
A water pump to get the nutrient solution from the reservoir into the grow tray
Hydroponic tubing
Net cups

How to Grow Hydroponic Onions Indoors

Firstly, fill a jar with water nearly to the brim and then mix in a vegetable fertilizer that was designed for Onions, being sure to follow the directions on the box.
Then, place an Onion on the jar so that its roots are pointed downward into the water. If the Onion is smaller than the mouth of the jar, and then insert a toothpick one-half inch into each side of the Onion, and then place the Onion in the jar.
If needed, add or remove water so that the waterline only covers the Onion’s roots.
After that, place the jar in a windowsill that receives sunlight for the majority of the day. If you do not have access to a windowsill with sunlight, and then place the jar under a grow light.

How Much Time It Take To Grow Onions Hydroponically?

Depending on what kind of Onions you are growing and whether you are planning on harvesting just the tops or the bulbs, it takes around 3 to 90 days to produce a crop of hydroponic Onions.

Green Onions are the fastest-maturing kind of Onions you can grow in a hydroponic system; take just 21 to 30 days to reach maturity. For any kind of Onions, seeds germinate in about 6 to 10 days.

Hydroponic Grow Media and Nutrients for Growing Onions

No matter which of these systems you select and regardless of whether you purchase a premade unit or build one yourself, you’ll also need growing media and nutrients for plant growth.

Onions are easy going when it comes to their nutrient needs they don’t need a lot of fertilizer. Though, you can supercharge their growth by adding some nutrients. Nitrogen is necessary you want to avoid adding too much as it will create lush foliage rather than bulbs.

If you add fertilizers, do this later on in the growing cycle rather than at the beginning, as it can stunt the growth of seedlings by burning them.

There are several options for growing mediums in hydroponics. You can use composite plugs, rock wool, or perlite. This depends on which system are you going to use and the Kratky system is the simplest one. Then, place the nutrient solution as it is inside the jar. No more steps are required; you have to just leave the Onion as it keeps using the nutrient solution till it fully grows.

When using a DWC hydroponic system, make sure to regulate the nutrient solution level so that it is not too high or too low. Avoid adding the nutrient solution to the newly transplanted Onion seedlings during the first period. This promotes more root growth that will later support Onion in further development.

The water reservoir requires nutrients essentially for Onions, it’s better to starve them during the initial stages, when the seedlings are growing. This helps establish a strong roots base for the plants and will increase plant growth. The balancing of nutrients can be tricky for Onions. Nitrogen is essential to plant growth but adding too much of it will neglect the Onion bulbs for the benefit of the foliage. And too little nitrogen will reduce the plant stamina and plant growth. Also, the supplying of proper nutrients is characterized by supervising the pH levels and electrical conductivity. The nutrient solution must be changed once every 3 weeks.

Conditions Required for Hydroponic Onion Farming

Generally, there are several materials you will need to get started with growing hydroponic Onions, including the Onion sets themselves, water, growing medium, net pots, water, air pump and stone, and a growing tray.

Nutrient pH level – 6.0-6.7
EC level – 1.4-1.8
PPM 980-1260

Onions are easy to grow in outdoor hydroponic systems. Also, they can be successfully grown in an indoor setup. Onions can be started from seed or set. An Onion set is an immature small Onion bulb planted instead of an Onion seed.

Growing Lights for Hydroponic Onion Farming

Short-day Onions are the most appropriate Onion variety for any hydroponic system. The short-day Onion variety needs an average of 10 to 12 hours of light per day, which is the shortest among all other Onion varieties. Also, using LED grow lights for its power efficiency.

pH Levels for Hydroponic Onion Farming

It is very important to maintain the pH levels of the water reservoir for the good growth of the Onions. About 6.0-6.7 are the preferred levels for optimal growth.

Chlorinated Water for Hydroponic Onion Farming

If you are using Chlorinated tap water in a hydroponic setup, it must be allowed to sit for 48-72 hours to dissipate the chlorine.

Prepare Your System and Net Pots

Start by filling net pots with your growing medium like perlite. Net pots have holes in the bottom and are designed to be used in hydroponics so that nutrients can get to the plants’ roots with ease. These pots make it easier for the solution to drain. We recommend using 3-inch net pots for this type of vegetable. Insert each Onion halfway into the medium, then insert pots into the grow tray. Let it fill with water before you add your air stone and this will add oxygen to the system.

Start Your Onion Bulbs or Seeds for Hydroponic Onion Farming

When you plant bulbs, try to do so at roughly the same height. At the same time, your roots will be adequately moistened. Also, you can start your Onions from seeds rather than from bulbs or sets, although this will admittedly take a bit longer. It will take 10 days for Onion seeds to germinate. Then, starting the Onion seeds on a sunny windowsill or under a grow light. Plant the seeds about ⅓ inches deep and ¼ inches apart.

After that, you can transplant into the net pots after around 30 days. Hydroponic Onions grow best in full sun, so if you’re using a hydroponic system indoors, you will want to give them about 12 hours of light per day via grow lights.

Temperature Requirement for Hydroponic Onion Farming

The perfect temperature level for hydroponic Onions is from 12°C to 23°C. Remember when we have chosen to grow short-day Onion varieties rather than intermediate or long-day ones. This variety is very tolerant to low temperatures. Thus, it will save you a lot of money on heating electricity bills every month.

Once Onions are planted, you won’t have to do much to care for them. Check your nutrient solution regularly, making sure the pH level remains at around 6.0-6.7. The water you use in your system should be unchlorinated, but if use chlorinated water, just let it sit out for 72 hours so the chemical dissipates. When you add nutrients to the reservoir, wait an hour, then check the pH to see if it needs to be adjusted. Finally, make sure hydroponic Onions have access to good air circulation. Otherwise, they can become rotted and mildew.

Air Circulation and Aeration in Hydroponic Onion Farming

Aeration is very important for hydroponic plants. Because they grow in high levels of moisture, if the air around them is not circulated properly, then it can lead to the growth of mildew or bacteria. And this can prove detrimental to your plants. For good air circulation, you can install exhaust fans or floor fans, or ceiling fans, or even keep a window open. You should aerate the solution continuously not only to keep hydroponic nutrients and discourage anaerobic bacteria but to oxygenate the roots as well.

The Best Hydroponic System for Onions

If growing hydroponic Onions begin by selecting your hydroponic system. Hydroponics set-ups are set up inside or in a greenhouse system. Setting up a growing environment will be relatively similar, but you will need lighting for an indoor environment whereas this might not be necessary for a greenhouse.

Selecting a hydroponic system to grow Onions can be a tough part. The hydroponic systems can be used to grow root crops like Onions they are Nutrient Film Technique, flood and drain (ebb and flow), Deep Water Culture and Kratky method.

DWC uses an air pump to distribute oxygen to your nutrient solution. DWC system will allow you to use separate grow trays or containers so that have a reduced risk of roots tangling up with each other or becoming diseased. Ebb and flow hydroponics is another great option. It’s best for plants that need prolonged periods of dryness and also works well with root crops like Onions.

Nutrient Film Technique for Hydroponic Onion Farming

NFT gives the ability to grow a high volume of plants and using less space compared to another hydroponic system. However, there are some critical modifications that you want to add before growing your first batch of Onions. Spacing is crucial for Onions. Then, you should provide the right spacing between each Onion to decrease the competition of light when the Onions leaves get tall in the harvest stage.

The proper spacing is about 4 feet between every 2 adjacent Onions. Then, you can customize it yourself or just buy a normal NFT hydroponic system and leave an empty pocket between every 2 Onions. The hydroponic Onion pots must be wider than normal pots. If the hydroponic pot is not wide enough, the Onion will grow from the inside or break the hydroponic pot and get stuck into the NFT pipe. You have got to make sure of the pot sizing before even starting to grow the Onion seedlings.

Deep Water Culture for Onions

DWC hydroponic system can be also a suitable choice to grow hydroponic Onions. It cannot be used to grow very high quantities of Onions and it remains a perfect choice for beginners.

Deep Water Culture hydroponic system is easy to manage with no particular complications. You need to keep the diameter of the hydroponic pot wide enough so that the Onion grows large, it doesn’t get stuck inside.

The Kratky Method for Growing Onions

Kratky methods have been used to put half-grown Onions into water jars and then leave them beside the glass window. Then, the water inside the jar gets used by the Onion as it grows larger and its leaves get taller. This method can be used to grow Onions as a decoration inside the kitchen. Also, it can be used as a cool project to learn about hydroponics.

If you do not have a DWC system for growing hydroponic Onions, instead you can employ the Kratky method. The benefit of this Kratky method is that it is ideal for plants that have a short life cycle, such as green Onions. The water level will drop as the plant roots grow, providing a growing zone of air for the roots. Growing Kratky Onions is an easy method to grow Onions and other hydroponic vegetables. It is ideal for fast-maturing plants like Onions, particularly if you want to be able to harvest multiple crops in a short amount of time.

The Process to Set up for Hydroponic Onion Farming System

Before you can start growing hydroponic Onions, you need to first decide which Onion seeds you’d like to start. Many people grow green Onions in this kind of setup since they grow quickly, though they are much smaller than regular Onions.

The below instructions will tell you how to start growing hydroponic Onions;

Firstly, you have to decide upon the spot where you’ll place your set-up. With Onions, you can grow them indoors or outdoors so depending upon what’s feasible for you, you can place your set up where ever.
The Onions can be grown directly from the stage of seeds or you can plant bulbs first. Using small Onions bulbs and then placing them in a growing containing medium outside the hydroponic set-up can be an easy method for you to go about it.
The growing medium for your Onion is a very important aspect. Growing media such as composite plugs or Rockwool or even just plain old soil will do when you first plant your small Onion bulbs. Once they grow a little, they can be inserted into the Hydroponic system. Place your Onion seeds or bulbs in their respective growing media.
You can use one of three methods to irrigate them. They are Onion seeds are tiny so you can either soak them in the water for a while or you can wet the seeds or you can simply place the Onion seeds in their growing media and carefully sprinkle water on top of them.
Now moving on to taking care of them, new Onions seeds do not need any nutrients. Nutrients can prove to be harmful to them. This is because the embryos in the seeds already have the nutrients and then the energy required by the seed to grow and this is what is used by the seed. Thus, adding more artificial nutrients would harm the plant.
The seedlings do not need fertilizers and they can harm the seedling by chemically burning them or stunting their growth.
Place these little cultivated Onion seeds in a dark and warm place for them to grow well. If they have begun sprouting into tiny plants, transfer them with their growing media into the Hydroponic set-up. While setting up a water reservoir, which you can easily make by yourself with simple items, make sure it is at least 6 to 8 inches deep. After that, setting up the seeds for the hydroponic system and the hydroponic set-up is ready; it is now time to begin using it for its purpose.

When and How to Harvest Hydroponic Onions

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While green Onion tops can be harvested in as little as 3 weeks from planting sets, you will need 80 to 90 days to harvest bulb Onions. Harvesting hydroponic Onions is not different from harvesting conventionally grown Onions. It’s the same rooting procedure that you have to follow.

The best time to harvest hydroponic Onions is the morning. Then, simply pull them up and they’re ready to use. If you see any flower stalks emerging from the Onions, that is a good sign that the Onions have stopped growing and are ready to be harvested. Another good indicator that hydroponic Onions have matured is that the foliage has turned yellow and tipped over. After harvesting your hydroponic Onions, let them dry to cure. To do this, lay them out on a flat surface with good air circulation and cool temperature levels. Store them in an old Onion sack out of direct sunlight and they should last for several months.

Hydroponic Onion Farming – Growing Guide

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