When you think “hydroponics”, the first vegetable that comes to mind is probably lettuce.
Leafy greens, and lettuce especially, are perfectly suited for hydroponic systems. They grow fast, produce well, and have a small footprint in your grow space.
Lettuce is the perfect first plant for hydroponic newbies beginners. There isn’t anything tricky or fancy about growing lettuce, and you can get started with almost no experience and very little money.
At the same time, hydroponic lettuce systems can be scaled and monetized incredibly well. Commercial growers across the world produce millions and millions of dollars of the stuff each year.
No matter where you are in your hydroponic journey, lettuce could be the right vegetable for your hydroponic garden.
Here is everything you need to know about hydroponic lettuce.
How To Grow Lettuce Hydroponically
Lettuce is one of the easiest crops to grow hydroponically and because of this, is usually one of the first plants newbies start with.
Step 1: Gather Your Materials
First, you need some supplies. You’ll need:
- Choose a hydroponics system (more on that below)
- Hydroponic nutrients
- A pH test kit
- Lettuce seeds
- A light source (natural sunlight or grow lights)
- A timer (optional)
- Growing medium of choice (Rockwool cubes or Rapid Rooters)
Step 2: Start Your Seeds
Next, you’ll start your lettuce seeds.
- Soak the Rockwool cubes in water until they’re completely wet.
- Put a few seeds into the hole on top of each cube.
- Keep the Rockwool cubes somewhere warm. The top of the fridge works well.
- In a few days, you should see sprouts!
Step 3: Set Up Your Hydroponics System
While your seeds are sprouting, set up your hydroponics system.
- If you’re using a DWC system, this means setting up a reservoir (a big container for the water), an air pump to keep the water oxygenated, and a lid with holes for the plants.
- Fill your reservoir with water.
Step 4: Add Nutrients and Check pH Now, it’s time to add nutrients to your water and check the pH.
- Follow the instructions on your nutrient package to add the right amount to your water.
- Use your pH test kit to check the pH of the water. It should be around 6.0. If it’s not, you can add pH up or down solutions to adjust it.
Step 5: Transfer Your Sprouts Once your seeds have sprouted, you can move them to your hydroponics system.
- Make sure the roots of your sprouts reach the nutrient water.
- Make sure the leaves are above the water.
Step 6: Provide Light Now, your lettuce plants need light to grow.
- If you’re growing your lettuce outside, make sure it gets 10-14 hours of sunlight per day.
- If you’re growing your lettuce inside, turn on your grow lights for about 14-18 hours per day.
Step 7: Monitor and Harvest The last step is to monitor your plants and eventually harvest your lettuce.
- Check the water pH and nutrient levels every few days.
- Refill the water when it gets low.
- Once the lettuce leaves are big enough, you can start picking them. Don’t take all the leaves from one plant at once, though. If you leave some, the plant will grow more.
Best Growing Methods for Hydroponic Lettuce
Lettuce can be grown in just about any hydroponic system. For beginners, I’d recommend starting with Deep Water Culture (DWC) and graduating to the Nutrient Film Technique (NFT) once you have a handle on growing and monitoring your system.
Deep Water Culture (DWC)
This is one of the simplest and most cost-effective methods for growing hydroponic lettuce. In a DWC system, the plant roots are suspended directly in a nutrient-rich water solution.
The water is oxygenated using an air pump, ensuring the roots don’t drown. This method is great for lettuce because it provides constant access to both nutrients and oxygen, which are essential for its growth.
DWC also requires less monitoring and adjusting compared to other systems.
Nutrient Film Technique (NFT)
In an NFT system, a water pump is used to create a thin film of nutrient-rich water that continuously flows over the roots of the plants, which are held by slanted, shallow channels. The angle allows excess water to drain off, reducing water usage.
This method is beneficial for lettuce because it gives the plant constant access to nutrients while also providing plenty of oxygen to the roots. However, NFT systems can be a little more complex to set up and manage, as they require a precise balance to ensure the roots stay moist but not waterlogged (causing root rot).
Remember that each of these methods requires careful monitoring and control of nutrient concentrations and pH levels in the water, regardless of which you choose.
Which types of lettuce are commonly grown hydroponically?
There are over a thousand lettuce varieties grown today. Of these thousand varieties, several types are incredibly common because of their flavor, color, disease resistance, and growth speed.
Here are some of the most popular types and interesting lettuces to grow hydroponically in your lettuce garden:
Butterhead
This variety of lettuce has bright green, velvety, slightly ruffled leaves and a sweet butter-like flavor, hence the name. Some types of Butterhead lettuce are dark green or red. Bibb and Boston lettuce are both types of Butterhead lettuce.
Romain
One of the most recognized and well-known varieties of lettuce, Romain has characteristically long leaves. The texture is crisp, and the flavor is slightly sweet.
Little Gem
Described as a combination of Butterhead and Romain, Little Gem is juicy with a thin center stalk that gives structure without too much crunch.
Lollo
Wide, frilly leaves and a loose head define Lollo lettuce. This is a popular variety for baby leaf production.
Another great thing about lettuce is that it grows well in tandem with other leafy vegetables and herbs. As long as the plants share similar nutritional needs, they can be grown in the same container or from the same reservoir.
Good things to grow alongside lettuce are spinach, kale, basil, mint, swiss chard, endive, escarole, arugula, watercress, and more.
Ready to grow some hydroponic lettuce? It all starts with quality seeds. Check out TrueLeaf Market for 20+ varieties of lettuce seeds!
Can I regrow hydroponic lettuce?
If you remove all of the leaves on a head of lettuce and leave it in a hydroponic system, it will continue to grow. This way, you can extend your yields and get great value out of each plant.
However, a better strategy—especially for home growers—is to periodically harvest lettuce leaves as they come in or as they are needed. If you remove the large, outer leaves and keep the rest of the plant intact, the head will continue to pump out new leaves.
This technique is called “cut and come again.” Using cut and come again, you can have fresh salads every day without the wasted time and energy of constantly replanting heads of lettuce from seed.
A head of lettuce will keep producing under these conditions for many weeks until it ultimately starts to bolt.
Bolting just means that growth in the lettuce quickly shifts from leaf growth to flower and seed growth. Because we are only interested in the leaves, bolting is bad for us growers. When your lettuce bolts, it’s time to pull it out and start anew.
How long does lettuce take to grow hydroponically?
Hydroponic growers love lettuce because it grows so quickly. You’ll start seeing lettuce seedlings in days.
Naturally, lettuces develop leaves incredibly quickly, but putting them in hydroponic systems is like super-charging them.
Almost all vegetables grow significantly faster hydroponically than they do when planted out in the field. This is because a hydroponic system is an extremely controlled and efficient environment for plants.
In hydroponics, light, temperature, water, and nutrition are all controlled to a T, so there’s nothing to hold your lettuce back.
Some varieties like Butterhead and Romain are ready to harvest in just three or four weeks.
Others, like Iceberg and denser, sturdier lettuces, are ready to harvest in six to eight weeks.
How many hours of light does hydroponic lettuce need?
Exactly how many hours of light any plant needs depends on the lights you are using and how close the lights are to the plant.
Think of it like filling a jug of water. It’s not just about the time that the faucet is on, but how much water is coming out.
In reality, getting to the bottom of a plant’s optimal light requirements is very technical.
Light is measured by DLI or daily light integral. DLI is calculated by measuring the photosynthetic photon flux density, which is how much light within the wavelength that plants need.
Luckily, hydroponic growers don’t need to be scientists to get the right lighting. The theoretically optimal lighting and enough lighting are very different things.
A great starting point for any type of lettuce is 12 or more hours per day.
Depending on the lights you use and your particular setup, you may need to bump this up or down. If you see signs of burn on your leaves, you can lower the number of hours of lighting per day. If you feel that your plants are growing too slowly, you can up the lighting.
You can use the table below to help guide you depending on the type of lighting you are using.
| Type of Light | Recommended Light Duration (Hours) |
|---|---|
| Natural Sunlight | 10-14 hours |
| Fluorescent Lights | 14-18 hours |
| Metal Halide Lights | 14-16 hours |
| High Pressure Sodium Lights | 12-16 hours |
| LED Lights | 14-18 hours |
Remember, lettuce is an incredibly easy plant to grow hydroponically. You don’t need to worry about having the perfect, optimum light cycle, just one that keeps your plants healthy.
What can I feed my hydroponic lettuce?
Hydroponic lettuce needs a high-quality nutrient solution to survive and thrive. A nutrient solution is made by combining a balance of hydroponic nutrients with purified water.
Read more about Hydroponic Nutrients & Fertilizers
Leafy greens like lettuce need plenty of nitrogen to grow. This is because nitrogen stimulates foliar growth or leaf growth.
At the same time, lettuce needs plenty of potassium for structure and to prevent wilting.
A good hydroponic fertilizer for lettuce that is super easy to use is this lettuce hydroponic mix.
This powder fertilizer has all of the essential macro and micronutrients that lettuce needs, you just need to add water. Two pounds of fertilizer is enough to make 128 gallons of nutrient solution.
Does hydroponic lettuce taste better?
Hydroponic lettuce may taste different based on the nutrients you provide it, the temperature, and several other factors, but in general, hydroponic lettuce and lettuce grown in soil taste the same.
However, when grown meticulously, hydroponic lettuce can have a better flavor than lettuce grown with any other method. This is because hydroponic growers have far greater control over the factors that influence flavor than growers who plant lettuce in soil.
At the end of the day, it all comes down to what you put into the plant and your personal preference. Most people don’t taste any difference at all.
Do you need to wash hydroponic lettuce?
Because hydroponic lettuce isn’t grown in soil and isn’t sprayed with pesticides, it doesn’t necessarily need to be washed.
The primary reason for washing vegetables is contact with soil. Soil can expose plants to E. coli and Salmonella, as well as other bacteria, fungi, nematodes, and insects. Also, the soil itself may be present on the plant, which no one wants to eat.
Because hydroponic veggies never touch the soil, they aren’t at risk for these pests and contaminants.
However, it’s possible for seeds to be contaminated and carry the contamination through the growth cycle and end up on the final product—but this is unlikely.
Depending on where your hydroponic lettuce comes from, you still may want to wash it. This is simply because the lettuce may have been handled by someone with unclean hands.
Why is my lettuce bitter?
Hydroponic lettuce may taste bitter for four reasons: temperature, nutrition, water, and age.
Lettuces are a cool-weather plant. When grown outdoors, lettuce tastes best during the spring and fall. In the summer heat, they undergo changes and start to bolt, creating a bitter flavor.
You can even notice a difference in flavor in lettuce that is harvested early in the cool morning, and late in the afternoon when the sun is out. The morning lettuce will taste sweet and the heat-burdened afternoon lettuce will taste bitter.
For outdoor hydroponic systems, this is a concern. If you aren’t controlling the temperature that your lettuce is grown in, you need to work with the sun or accept the occasional bitter head of lettuce.
Indoor growers usually won’t have temperature problems. Unless their grow lights are throwing off too much heat onto their lettuce heads.
In this case, the solution is to turn down the thermostat or give your plants some space by changing the height of your grow lights.
Another reason your lettuce is bitter is because of nitrogen deficiency. Boosting the nitrogen levels in your nutrient solution can fix the problem.
Next, a lack of water will cause bitterness. Plenty of water is needed to keep leaves sweet and full.
Lastly, lettuce becomes more bitter with age—there isn’t any getting around this. When your plant gets old and begins to taste bitter, it’s time to harvest and plant a new seedling in its place.
What is the best nutrient for hydroponic lettuce?
All of the macronutrients, nitrogen, phosphorus, and potassium, and many micronutrients are essential for healthy lettuce growth.
To supply the right balance of nutrients to your plants, you will need the right hydroponic fertilizer. A fertilizer high in nitrogen and potassium will work best.
For new growers, the easiest and most effective option is to get a premade dry mix of nutrients specially designed for lettuce. This will have the right balance of macro and micronutrients for lettuce and doesn’t require any special knowledge of fertilizers.
For more advanced growers, the best option is to make a dry fertilizer mix yourself. Getting the separate ingredients in bulk and measuring and mixing yourself will save you loads of money long-term and give you the most flexibility when it comes to plant nutrition.
A great all-in-one option is the Masterblend Complete Combo Kit Fertilizer. This package includes a 4-18-38 Tomato and Vegetable Formula, 15.5-0-0 calcium nitrate fertilizer, and Epsom salt.
By mixing one part Tomato and Vegetable Formula, one part calcium nitrate, and one-half part Epsom salt with pure water, you get a hydroponic fertilizer concentrate that can be diluted and make an incredible nutrient solution.