Hydroponic Lettuce 101 – Guide To Perfect Greens

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 you. 

Here is everything you need to know about hydroponic lettuce.

Which varieties of lettuce are commonly grown hydroponically?

There are over a thousand varieties of lettuce 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 and interesting lettuces to grow hydroponically:

Butterhead

Butterhead Lettuce
Naraporn Muangwong | Dreamstime

This variety 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

Romain Lettuce
Kaiskynet | Dreamstime

One of the most recognized and well-known lettuces, Romain has characteristically long leaves. The texture is crisp, and the flavor is slightly sweet.

Little Gem

Little Gem Lettuce
Sjankauskas | Dreamstime

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

Lollo Lettuce Head
Pipa100 | Dreamstime

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.

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, outermost 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. 

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 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.

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 Greens and Herbs 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 the 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.