Growing Hydroponic Lettuce: Expert Tips for Easy and Productive Harvests

Hydroponics and lettuce is a match made in heaven. If you want to grow your greens leaves at home or in your back garden, if you choose hydroponics you will have a better yield than if you grow lettuce in the soil, you will reduce the risk of pests, and you can also utilize space more efficiently. In fact, lettuce has been grown hydroponically for decades, and with great results.

Growing lettuce hydroponically is easy; even a complete newcomer to this type of gardening can do it successfully.

However, you will need to choose the right hydroponic system, set it up correctly, and then understand the basics of hydroponic gardening.

So, if you want to have lettuce ready for your dinner table from your back garden or even straight from your kitchen, and you are thinking about setting up a hydroponic garden, look no further.

In this article, we will look a how you can choose the best hydroponic system for your lettuce, how you can set it up, and how you can care for your plants from birth to harvest.

Three Things You Need to Know to Grow Lettuce Hydroponically

Each (hydroponic) garden is different; so is each variety of lettuce. But if you want to succeed with your crop, there are three main areas of expertise you will need:

Choosing the place and appropriate hydroponic system: there are many systems available, and some are better for some crops, others for other vegetables. Similarly, some are better for small indoor gardens, others for large outdoor ones…
Setting up your hydroponic system; this may look daunting to some, because it sounds very high tech; in reality, it is quite simple, but you need to know how to do it.
Looking after your lettuce and hydroponic garden; this too, is very important, but hydroponics does not require a lot of maintenance and lettuce is fairly easy to care for.

So, we will look each in turn, starting… now!

Growing Lettuce Hydroponically: Making Choices

You will need to choose your hydroponic garden and place very carefully; as with most things in life, making a good choice at the start of your experiment can make all the difference between a pleasant and successful experience and a frustrating and disappointing one. This is true also if you want to grow lettuce hydroponically.

Choosing The Place For Your Hydroponic Lettuce Garden

The place where you want to grow your lettuce hydroponically is all important. There are a few factors you will have to weigh properly:

Is the space indoors or outdoors? Hydroponics is more common indoors or in greenhouses, still, it can be suitable for outdoor spaces as well. The main difference will be the light. Lettuce does not want strong light, and, if you grow it indoors, you will need plenty of blue light, if you use grow lights.
Do you want your hydroponic garden in a living space? Sonde systems are better suited for living spaces than others. This is because some, like ebb and flow, can be a bit of a nuisance as the pump may be a bit noisy. The size of tanks etc. too will affect your choice.
Is the space big or small? Limitations in space also limit your options, of course.

In any case, remember you will be growing lettuce: it is a fast growing leaf vegetable, but it has its needs; lettuce does not like hot places in direct sunlight all day long, especially indoors. Too much light can lead to leaf urn and edge burn

If outdoors, allow about 10 to 12 hours of daylight. If indoors, keep your lettuce away from direct light, and especially from South facing windows.

The Best Hydroponic System To Grow Lettuce

Choosing the right system for your lettuce garden is very important indeed… There are many available, but lettuce has its own requirements… While it can grow in a deep water system, it is not the most efficient, and if you choose this one, your lettuce is more likely to catch disease. On the whole, I would limit the choice among three systems:

Ebb and flow; this is excellent especially for large plants, if you have plenty of space and outdoors. Indoors, however, it is not ideal to make the best use of space and the irrigation cycles can be a nuisance in loving spaces.
Drip system; my favorite for many reasons; irrigation is provided gently and regularly, it can be adapted to any size and shape of space; it is silent (the pump does not need much pressure, so it does not make much noise); it recycles the nutrient solution efficiently…
Aeroponics; this advanced hydroponic system is actually excellent for lettuce and it gives excellent yields, it prevents pathogens from spreading, and it actually uses less water and nutrient solution. However… It is not very suitable for outdoors and it is hard to keep the atmospheric conditions inside the vapor chamber stable if you have a small garden.

There are, of course, other available systems, like the nutrient film technique, but if you are totally new, and you need some general advice, I would go for a drop system. It’s easy, safe, efficient and effective.

The Best Grow Lights For Your Hydroponic Lettuce

If you want to grow your hydroponic lettuce indoors, you may need grow lights in case you can’t offer your plants the right light exposure with your windows.

The best grow lights are LED lights; you can get them in all sizes and shapes, with a timer and you can regulate the intensity of the light in many cases.

But there is more; these lights do not heat up your leaves and they provide the full spectrum of light that plants need. Did I say that they also last long and use very little electricity?

In any case, choose lights that have the blue spectrum: leaf vegetables and short day vegetables (and lettuce is both), use more light in the blue spectrum than in the red one.

Setting Up Your Hydroponic System

Have you found a hydroponic kit that suits your needs and your lettuce plants? Or maybe you are a DIY geek and you want to build your own… Well, in the second case, you will need some knowledge of hydraulics to do it, but you will still need to set it up. So, follow these easy steps…

The Elements (Parts) Of Your Hydroponic System

First of all, you will need to know what your hydroponic system consists of, its elements or parts. Here they are:

The reservoir, also known as sump tank, is the “working hub” of your hydroponic garden. Everything starts from there and in many cases leads back to it… This is where you store your nutrient solution (water plus nutrients).
The grow tank is the actual “flower bed” of your garden; this is usually a tank, but it can be a tower, or pipes, or even individual buckets. In it, you usually have mesh pots for individual plants in which you will need to put a growing medium.
The water pump; this is of course what brings the nutrient solution to your plants.
The air pump; this is necessary to oxygenate the nutrient solution because roots breathe as well.
The timer; you will need one with ebb and flow, drip irrigation, aeroponics and nutrient film technique and aeroponics. It will determine when and for how long you irrigate your plants.
Grow lights are often necessary indoors.
The thermometer will tell you what the temperature of the nutrient solution is (the roots of plants don’t like too cold or too hot).
The EC meter measures the electrical conductivity (EC) of the nutrient solution. This is very important because it shows how rich in nutrients is your nutrient solution. So, if it drops, you will need to change the solution.
The pH gauge or meter, which you will need to know the pH of the nutrient solution.
Pipes connecting the various elements.

Now you know what is what and how each element functions, we can actually start setting yup your garden.

Eighteen Easy Steps to Set Up Your Hydroponic Garden

Ready to watch your hydroponic garden come together? We can now start setting it up, but first, clear the space for your garden and take a deep breath… Here are eighteen easy steps to set up your garden:

1. Position The Reservoir

To start with, choose a good position; this may be under your grow tank, or in any case, if indoors, mainly out of sight. Still, don’t put it where it’s hard to work, as you will need to come back to this regularly during the life of your crop.

2. Place The Air Pump’s Stone In The Reservoir

If you use an air pump, the first thing you will need to do is put the air stone in the reservoir. Put it in a central position. The air pump is not necessary with drip cultures and with aeroponics though.

3. Connect The Air Pump

Then, you can connect the air pump to the mains.

4. Set The Water Pump And Timer

Now, you will need to set the water pump and the timer… This is not hard but you need to insert the timer into the mains and then the pump into the timer’s socket. Don’t switch anything on yet, but set the timer.

5. Connect The Water Pump To The Reservoir

Now, place the in-pipe of the pump into the sump tank (the reservoir). Make sure it reaches to the bottom of the tank, otherwise it will not fetch all the nutrient solution.

6. Fill Up The Reservoir

You can now fill the tank with water. On average, for lettuce, you will need about ½ gallon of water per plant.

7. Use A Good Nutrient Solution

A good nutrient mix for lettuce is, for every 5 gallons of water, 2 teaspoons of 18-15-36 NPK organic fertilizer and then 2 teaspoons of calcium nitrate and 1 teaspoon of magnesium sulphate of you want to make your own.

Dissolve the calcium nitrate and the magnesium sulphate in a cup of warm water each before mixing them to the nutrient solution. Alternately, a good leaf vegetable nutrient mix will do.

8. Prepare The Nutrient Solution

Mix in the nutrient mix; the exact quantities will be on the container. On average, however, a few teaspoons of nutrient very 5 gallons of water.

The average for this vegetable is between 560 and 840 ppm, or parts per million, so, very little indeed. If you only grow lettuce, it’s best if you use a lettuce specific nutrient.

9. Stir The Nutrients In The Water

Mix the nutrients in the solution with a stick! Remember this step… they won’t mix themselves…

10. Place The Thermometer

Insert the thermometer if you use one; clip it to the side of the reservoir. The best temperature for lettuce is between 60 and 75^o F, which is roughly 16 to 24^o C.

11. Place The PH Meter

You can measure the pH every time you check your tank, but if you want to clip it to the sides of your reservoir, you can now.

12. Prepare The Mesh Pots

Now, put the growing medium in the mesh pots.

13. Plant Tour Lettuce

Plant your seedlings in the mesh pots.

14. Connect The Pump To The Grow Tank

Check the Grow Tank and the Lettuce Plants

Connect the out pipe of the pump to the grow tank. This is the “garden proper”, where you have the plants in the mesh pots. If it is a drop system, you will just have to connect the pump to the piping.

15. Don’t Forget The Recycle Pump

Connect the recycling pipe from the grow tank to the sump tank.

16. Close The Reservoir

Now, if you have one (good idea), put the lid on the reservoir.

17. Set And Adjust The Grow Lights

Yes, if your garden is indoors, it is a good idea to switch the lights on first… Set the lights at a safe distance from the plants.

This is usually about 12”, but some gardeners do put LED lights closer, this is especially if they are soft, because they don’t heat up as much.

With lettuce, however, I would be very careful about risking it. Make sure that the light reaches every corner of your grow tank…

In case, adjust the lights. You may need a timer with some lights, in case, plug the timer into the mains and the lights into the timer, like you did with the water pump.

18. Start Your Garden!

Finally you can get your hydroponic garden going! Just switch on the air pump, then the water pump, then the lights. That’s it… Your hydroponic garden will be doing most of the hard work for you from now on!

Hydroponic Garden Maintenance and Lettuce Plant Care

The hardest bit is now behind you: all you need now is to carry out some routine maintenance work and give basic care to your lettuce plants.

This is one of the beautiful things of hydroponics: once the garden is set up, you will literally only need a few minutes a day to look after your plants.

In fact, there are things you will not need with hydroponics:

There is no weeding with hydroponics.
Hydroponic plants tend to be disease and pest free. It is very rare that plants will become unhealthy.
Your garden will do the watering for you.
No need to care for the soil with hydroponics.

Still, there are e few things you will need to do, and this is exactly what we are going to learn.

1. Check The Grow Tank And The Lettuce Plants

You should check your plants and tank regularly; it only takes a few minutes, but you want to keep an eye on your beloved leaf vegetables, so…

Sample some lettuce plants; take them out of the pots and check their roots for any sign of disease, like rotting, and check that the roots are growing well.
Keep an eye out for algae growth in the grow tank; just look for any signs of small algae, like those green and sleek layers that grow on the sides or walls of your grow tank. Some is inevitable as well as innocuous. Don’t worry about a few algae in your garden. Only act if the growth is excessive. The good thing with lettuce is that is is fast growing, so, the chances are that you will be able to wait till you change crop to clean the grow tank.
Check that there are no clogs; this is fairly rare and it happens more with Bebe and flow than other systems. Still, do have a look at the pipes’s mouths and check that they are not clogged. Once a week is more than enough.

2. Check The Nutrient Solution

Checking the nutrient solution is arguably the most important job of any hydroponic garden.

You see, you send a mix of water and nutrients to the roots of your lettuce (actually, the pump does it for you). The roots then take up some of the water and some of the nutrients.

But they don’t take up a proportionate amount of both in most cases. It usually happens that they absorb more nutrients than water in proportion.

So, the nutrient that gets back to your tank is usually diluted. This is fine up to a point, then, it becomes too poor in nutrients to sustain your crop.

3. Use The EC Meter To Check The Nutrient Solution

How can you check that the nutrient solution is fine? You need to understand how the electrical conductivity of water and solutions works.

Pure water has electrical conductivity of 0.0, zero… If you add minerals, the conductivity increases. So, the richer your solution is in nutrients the higher the EC level.

The EC level for lettuce must be between 0.8 and 1.2.So, in practical terms, how can you go about it?

Measure the EC level in your reservoir daily. At least, start daily, then you can adjust and adapt if it does not vary much.
Always write down the EC level when you measure it. Any change can tell you what is happening to your nutrient solution and your plants.
If the EC level goes above 1.2, add water and stir. This means that either the plants were thirsty, or that the solution is drying up because of heat.
When the solution’s EC level drops under 0.8 you have two options. Experienced hydroponic gardeners learn how to top it up. Alternatively, you can just empty the tank and refill it with new solution, especially if it is low. Don’t worry, using organic nutrients means you can literally pour it down the toilet.

4. Check The Reservoir For Algae

Algae may also grow in your reservoir, especially if it is not Matt and dark and it lets the light through.

Inspect the reservoir regularly for algae growth. In most cases, this will be no problem, like with the grow tank.
Unless it is extremely urgent, wait till you change the solution to clean the tank.
If your reservoir is translucent, cover it black or dark material (anything from plastic to cotton will do, or even cardboard).

5. Check The PH Of The Nutrient Solution

The pH of the solution changes not just the EC, but also how your lettuce plants absorb nutrients. This is a very important point to keep in mind.

The wrong pH means that your plant will absorb too much of some nutrients and too little of others.

The correct pH for hydroponic lettuce is between 5.5 and 6.5.

Check the pH in your reservoir’s nutrient solution every three days.
Every time you check the pH, note it down.
If the pH is wrong, you can adjust it. There are organic “pH up” and “pH down” products you can use, or, to raise your pH, you can use a “home remedy” like a few drops of vinegar in the water. Low pH is common, because very often, tap water is “hard” (alkaline). In any case, always add a few drops at a time till you get the right pH.

Always check the nutrient solution’s pH after changing or correcting the nutrient solution.

6. Check Your Pump And Plumbing

Any clog or holes, malfunction or breakage in your water pump or pipes and hoses can be a real problem.

Fortunately, these problems are very rare, and you are unlikely to meet them with your first crop, your second, your third… Especially if you grow lettuce…

Still…

Set aside a few minutes every week to inspect pump and plumbing.
Check all the junctures, the in and out mouths of pump and all pipes and pipes or hoses.
You can find a clog by checking each irrigation hole or nozzle; start from the last one, if that works, all the ones before it are fine. If it does not, move to the one before, than the one before etc. till you find where the problem is. This is true of leaks as well.
If there’s a leak, in most cases you can repair it; only change the nose etc. if necessary.

7. Keep A Close Eye On The Lights

Lettuce is very sensitive to excessive light, so check the leaves regularly for signs of:

Yellowing
Browning
Drying
Burning
Drooping
Softening

Any of these and all of these can be caused by excessive heat and light. Adjust your grow lights accordingly or, if they are outdoors or they receive light from a window, shade your plants. Shade nets are perfect for this, but you can be creative.

8. Ventilate Your Plants

Lettuce is a very sensitive plant to weather conditions. While it likes fresh air and ventilated conditions, it does not like structure air and heat.

So, open your windows as often as possible, and give your plants a breath of fresh air.

9. Changing Crops

Your hydroponic lettuce will be ready in a matter of weeks. What then? Whichever crop you decide to plant, you will need to clean and sterilize the whole system.

To start with, remove the growing medium and wash it and sterilize it (water and alcohol will do).
Check for algae and blockages.
Run the system with water and a natural antibacterial, fungicide and pesticide; the best choice is neem oil, as it has all these properties but it will not harm your plants. And it’s fully natural and organic, of course.

Now your garden is ready for a new crop!

Hydroponic Lettuce from Seedling to Your Salad Bowl

This is all you actually need to go from a small plant to a fresh, leafy and wholesome green salad with your own lettuce using hydroponic gardening.

It may look like it’s a lot, but hold on – once you have set up your garden (and that can be an excuse for an hour of quality time with your kids), the rest is literally a few minutes a day…

All the different activities will become second nature to you in a matter of days, and they will become a relaxing activity very soon.

They are not difficult… It’s just that, like with every craft, you need to know them and be responsible with your hydroponic garden.

But, hey, nothing can match the pleasure of serving your guests with your own, organic and home grown lettuce at your dinner parties!

Written By

Adriano Bulla

After many years as an academic in London, Adriano Bulla became a writer, publishing books like A History of Gardening, Organic Gardening and Elements of Garden Design; he then decided to become a gardener, following his childhood dream, and has been following his dream writing and gardening professionally in Southern Europe, where he has specialized in new and innovative organic gardening fields and techniques, like permaculture, regenerative agriculture, food forests and hydroponics.

2 Comments

Huseyin TABAK says:

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Hello Mr Adriano,

I am a hydroponic agriculture entrepreneur, I built a 176 m2 1900 root lettuce greenhouse in total, what is the water requirement for 1 lettuce, what should be the irrigation period, can you help?

Denisa @PonicsArea says:

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Hi Adriano,

This is such a complex guide on growing hydroponic lettuce, it was a joy to read. Plus, I loved it even more when you said that the drip system is your favorite for many reasons. I totally agree, it’s awesome, especially for advanced growers. But beginners can also be comfortable knowing that lettuce can also be grown with the Kratky method using mason jars. It’s especially awesome for those who don’t want to invest too much money in the beginning.