How To Grow Hydroponic Green Onions

Milosh Potikj | February 15, 2024 | 8 MIN READ

Growing hydroponic green onions is an efficient and space-saving method to produce fresh, flavorful greens right in your own home. This guide will walk you through the essentials of setting up your hydroponic system, selecting the right nutrients, and ensuring optimal growth conditions for your green onions.

By harnessing the power of hydroponics, you can enjoy a continuous harvest of green onions without the need for soil, significantly reducing pests and diseases.

Even if you're an inexperienced grower, this step-by-step process will ensure your green onions thrive, providing you with a fresh supply for your culinary creations.

Starting Green Onions Hydroponically

Starting Green Onions Hydroponically

When starting green onions hydroponically, you have two options: you can start from seeds or from cuttings. Each method has its own benefits and requirements, so choose the one that best suits your needs and preferences.

Starting From Seed

Growing green onions hydroponically starts with seeds. Choose high-quality seeds for a successful crop.

  • Pick the right type of seed for your hydroponic system, like seeds specifically labeled for hydroponic cultivation or bunching onions.
  • Place the seeds in a small container with dampened rock wool or coconut coir to begin germination. Light and temperature control are important here.
  • Keep your seed-filled containers in a warm area but out of direct sunlight until sprouts appear.
  • Once seedlings sprout, move them under grow lights so they can get enough light without getting too hot.
  • Water these sprouts lightly with plain water at first. After about a week, start using a weak nutrient solution.
  • Gradually increase the strength of the nutrient solution as your green onion seedlings continue to grow.
  • Transplant these young plants into your chosen hydroponic system once they have grown strong roots. This helps them adapt without stress.

Starting From Cutting

After covering seed starting, another method to grow green onion hydroponics is from cuttings. This approach is both quick and straightforward. Here's how you can do it:

  • Cut a bunch of store-bought green onions, making sure each piece is about 6 inches long.
  • Look for healthy white roots at the bottom of each cutting.
  • Fill a container with water and submerge the root ends of the cuttings.
  • Change the water in your container every few days to prevent bacteria and algae.
  • Wait for new green shoots to appear over a couple of weeks.
  • Check your cuttings often for any signs of pests or disease.
  • Transfer these sprouted cuttings to your hydroponic system once they've developed shoots.
  • Use this same process to regrow them from leftover white roots, leading to an ongoing supply.

Growing Green Onions in Different Hydroponic Systems

Growing Green Onions in Different Hydroponic Systems

You can grow green onions using different hydroponic systems such as the Media Bed method, Nutrient Film Technique (NFT) System, and Deep Water Culture.

Media Bed Method

Green onions thrive in the Media Bed hydroponic system. This method uses items like expanded clay pellets to support the plants. These pellets let water flow around the green onion roots, giving them plenty of oxygen. Strong aeration stops root rot, keeping your green onions healthy.

In this setup, keep an eye on pH and EC levels to make sure your onions grow well. Media Beds are great because they stay at a consistent temperature, which is key for growing green onions. They create just the right conditions for your plants to do their best in a hydroponic garden.

Nutrient Film Technique (NFT) System

The Nutrient Film Technique (NFT) is a great way to grow hydroponic green onions. In this system, a shallow stream of water containing all the dissolved nutrients necessary for plant growth flows past the bare roots of plants in a watertight trough.

This constant flow means that the onions get an endless supply of water and hydroponic nutrients without being submerged, which keeps them from rotting.

Roots dangle in the nutrient solution as they move along, allowing them access to both nutrition and oxygen. Aeration is key here; it prevents root rot by ensuring that green onions have enough air while they grow.

Because NFT doesn't require a large volume of water or growing media like some other methods, it's often chosen for its efficiency and lower resource demands. This makes NFT popular among those who want fresh greens with less waste and maintenance.

Deep Water Culture

To transition from the Nutrient Film Technique (NFT) System to Deep Water Culture, it's important to note that Deep Water Culture (DWC) is a favored hydroponic system for cultivating green onions.

In this method, plants are suspended above a nutrient solution, allowing their roots to dangle and absorb vital nutrients directly. Aeration is crucial in DWC as it prevents root rot, which could damage green onions.

These plants require consistent access to water, nutrients, and oxygen for optimal development. Temperature maintenance is also essential – any fluctuations can have adverse effects on green onion growth in a DWC system.

Read More: How To Grow Hydroponic Plants

Necessary Conditions for Growing Hydroponic Onions

Necessary Conditions for Growing Hydroponic Onions

To successfully grow hydroponic green onions, you will need an indoor growing space with proper temperature and humidity levels. Additionally, you will also need the right hydroponic grow media and nutrients to ensure healthy growth.

Indoor Growing Space

For successful indoor growing, ensure a constant supply of water, nutrients, and oxygen. Proper aeration is vital to prevent root rot. Green onions thrive in consistent temperatures indoors.

Hydroponic Grow Media & Nutrients

Hydroponic Grow Media & Nutrients are essential for the successful growth of green onions.

  1. Use an inert growing medium like perlite, vermiculite, or coconut coir to provide support and aeration to the roots.
  2. Provide a balanced hydroponic nutrient solution containing essential elements such as nitrogen, phosphorus, potassium, calcium, magnesium, and trace minerals to support healthy growth.
  3. Maintain proper pH levels between 5.8 and 6.3 to ensure optimal nutrient uptake by the green onions.
  4. Consider adding organic supplements like seaweed extract or fish emulsion to enhance flavor and nutritional value.
  5. Monitor and adjust nutrient levels regularly based on plant growth stage and environmental conditions.

Read More: How To Grow Hydroponic Strawberries

Maintaining the Hydroponic Environment & System

Maintaining the Hydroponic Environment & System

  1. Regularly check the nutrient solution's pH and electrical conductivity (EC) levels to ensure they are within the appropriate range for green onions, which is generally between 5.5-6.5 for pH and around 1.2-2.0 mS/cm for EC.
  2. Provide adequate aeration to the nutrient solution using air pumps or air stones, as this helps prevent root rot and ensures that the roots receive sufficient oxygen.
  3. Monitor and maintain consistent temperatures in the hydroponic system, aiming for an optimal range of 65-75°F (18-24°C) during the day and slightly lower at night to support healthy growth.
  4. Regularly clean and sterilize the hydroponic equipment and system components to prevent the buildup of algae, bacteria, or other contaminants that can harm green onions.
  5. Conduct routine checks for any signs of nutrient deficiencies, pests, or diseases, promptly addressing any issues that may arise to ensure the continued health and vitality of the green onions.

Harvesting Hydroponic Green Onions

Harvesting Hydroponic Green Onions

Harvest green onions when the tops reach about 6 inches in height for optimal freshness.

  • Use clean shears or scissors to cut the green onions just above the root line.
  • Ensure the remaining roots and a small amount of bulb are left intact to promote regrowth.
  • Rinse the harvested green onions with cold water to remove any debris or dirt.
  • Store the harvested green onions in a cool environment with high relative humidity to maintain their freshness.

Storing Green Onions

To store green onions, ensure aeration to prevent root rot. Store them in a cool environment with high humidity at 32ÂşF. Harvest green onions when their tops reach about 6 inches for better storage. For optimal storage, wrap the green onions loosely in a damp paper towel and place them in a breathable bag or container before refrigerating.

This method helps maintain moisture while allowing for sufficient air circulation. Avoid washing the green onions before storage to minimize the risk of mold growth, and ensure they are dry to the touch. Regularly check and remove any wilted or damaged parts to keep the rest fresh for longer.


In conclusion, hydroponic green onions offer a productive and efficient method for year-round growth. Starting from seeds or cuttings provides options for cultivation. Three popular hydroponic systems, including Media Bed and Nutrient Film Technique, provide suitable environments for growing green onions.

Proper monitoring of pH levels, consistent water supply, and oxygen availability are crucial factors in maintaining a healthy hydroponic environment. Regular inspection for pests and diseases, along with proper spacing, ensures successful green onion cultivation.

Frequently Asked Questions

What are the best varieties of green onions for hydroponic cultivation?

Some suitable varieties include Evergreen Bunching, White Lisbon, and Apache.

How long does it take for green onions to be ready for harvest?

Green onions can be harvested within 20 - 30 days after planting.

How often should nutrient solution be changed in a hydroponic system?

It is recommended to change the nutrient solution every 1 - 2 weeks to maintain optimal growth.

Can green onions be grown alongside other plants in a hydroponic setup?

Yes, they can be grown with lettuce, chives, and some types of tomatoes due to similar growing conditions.

What is the ideal pH level for the water in a hydroponic system for green onions?

The optimal pH range is between 5.5 to 6.5 for healthy growth.

Can green onions from grocery stores be used as cuttings for hydroponic cultivation?

Yes, but ensure they are organic and free from any diseases or pests before using them as cuttings.

Should the water temperature in the hydroponic system fluctuate during different growth stages of green onions?

It's important to maintain consistent water temperatures between 65°F (18°C) and 75°F (24°C) throughout their growth cycle.

What are common issues or diseases that affect green onions when grown hydroponically?

Common problems include root rot due to overwatering or poor aeration and leaf discoloration caused by nutrient deficiencies.

What do I need to start growing hydroponic green onions?

To start, you'll need onion sets or transplants suitable for a hydroponic system like an ebb and flow system or aeroponic or aquaponic setups within your greenhouse.

How does the ebb-and-flow method work for growing green onions?

The ebb-and-flow method floods the roots of your green onions with nutrient-rich water at intervals and then lets it drain away. This helps them grow without soil.

Can bulb onions also be grown in hydroponic gardens?

Yes, you can grow both bulb onions and green onion varieties in hydroponic gardens by transplanting small bulbs into the system.

Do I need to germinate onion seeds before transplanting them into a hydroponic garden?

It's best to germinate onion seeds in a separate horticultural medium first; once sprouted, they are ready for transplanting into your hydroponic setup.

Is it possible to use furrows in a hydroponic environment for vegetables like green onions?

In typical soil gardening, furrows are used, but this term isn't relevant in a water-based system such as hydroponics, where plants get nutrients directly from the solution they grow in.


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