Best Method to Grow Hydroponic Lettuce at home

How to grow hydroponic lettuce

Most of us when starting with hydroponics look for vegetables and fruits that we can grow at our home hydro garden. So, I am covering all the information that you need to start growing your own fresh and organic hydroponic lettuce at home. 

We will be using the Kratky method to grow our hydroponic lettuce. It is because it is the easiest and the cheapest method to start with and will not require much effort during the whole period. The Kratky method is a hydroponic technique to grow plants in a passive way by hanging them over the reservoir filled with hydroponic nutrient solution. This method is great if you are a beginner and have very little experience in hydroponics. You can easily use this method to grow hydroponic lettuce at home.

We will discuss the advantages and disadvantages of growing hydroponic lettuce using the Kratky method later in this article. So the things you’ll need for this method are mentioned below.

Equipment Required to grow Hydroponic Lettuce

1-Two 25-liter tubs

So the tubs are dependent on how much lettuce you want to grow within the system each lettuce takes between three and six litres roughly equating to about four litres each so we’re going to try and grow six lettuce within this 25-litre tub

2- Multi-use extruded foam paneling

Now you want to make sure it’s extruded foam and not expanded foam because this has consistency throughout the board. Expanded foam can have air pockets which will lead to a non-uniform airflow. Extruded foam is a really useful foam for people who are starting with their hydroponics journey as it can be used later in other methods like a floating raft. Hence reusability is very important.

3- A Hole Saw

While Extruded foam is easy to cut and you don’t require a drill machine all the time but in case you are looking for uniform holes and want to use that foam for other purposes a drill would give a really smooth finish. You can also use a pipe the same size as your neck cup slightly smaller and sharpen the end and push it directly through the foam

4- Net Cups or Grow Pots

You’ll also need some net cups but you’re not limited to net cups here you can use nursery tubes or really anything that will hold medium in such a way that it still allows water to enter in and the roots to penetrate through and down into the nutrient solution.

5- Grow Media

You will also be needing some kind of growing medium whether it’s rock wool cocoa perlite which by the way I will be using in this example. Vermiculite, Perlite, or anything really that holds a plant in place can be used to grow hydroponic lettuce. I will be using cocoa perlite because it has a really nice wicking action if you have the bottom slightly submerged within the nutrient solution. If you don’t know what grow media is, do check out this article where I have covered the complete basics of hydroponic grow media.

6- Organic Lettuce Seeds

You will require some organic seeds. You can either order them from Amazon or get them from the local hydroponic store. You can also make your own seed from drying out the plants with flowers. 

7- Nutrient Solution

To power up the growth of your plant, you need to give it some good food in the form of nutrients. Many nutrient formulations are available in the market. Growing lettuce doesn’t require too many nutrients but still, you need enough of it to successfully harvest. 

8- pH meter

9- EC meter

10- Grow Lights

In case you want to use grow lights otherwise natural sunlight is also good.

Also Read – “Top 10 Common Hydroponic Terms You Should Know”

Let’s make our hydroponic system ready to grow lettuce at home. I have consolidated the process in certain points for better understanding.

Steps To Grow Hydroponic Lettuce at Home

Setting the design

Now before starting hydroponic lettuce seeds in this system, let’s get to marking out the size we’re going to cut on our foam boards and place them over our containers and you can literally just use a kitchen knife to cut through this foam board. To make it easy just put your net cups in the order that you want to grow the lettuce and mark the cup size with a marker and cut the perfect holes. 

Mixing Grow Medium

Now we need to mix up our growing medium which is 60:40 cocoa perlite in our case and put it in the net cups. You just need to fill the pots loosely and place them into the extruded foam. 

So the grow media mixture we are using here is inert media. The perlite is there to give it some aeration and the cocoa peat is there to wick up the nutrient from the reservoir. There is no nutritional content in this and it’s literally just there to give structure for the roots and also to provide moisture to the seeds in the germination phase of their life cycle.

We will be aiming to have the water level will just at the bottom of our net cups allowing the medium to wick up and there will still be an adequate amount of oxygen within the media whilst also giving the seeds the moisture they need to germinate so there are a variety of mediums that you could use in place of coco perlite just use the one that’s cheapest for you. Mother Earth coco perlite mix 70:30 is also good to use if you want to buy a ready-made mix from Amazon.

Note: don’t use anything organic like soil or seed raising mix as it is not sterilized. Rock wool, cocoa, perlite, vermiculite, all of these are good starter mediums. You can even start in hydrogen clay balls but it’s better that you start your seeds in cocoa perlite or starter plugs and then transplant them into hydrogen clay balls. 

Here are the recommended parameters for growing hydroponic lettuce. These can be used if you are growing lettuce inside a grow tent.

Air Temperature24 C Day/ 19C Night (75 F / 65 F)
Water TemperatureNo higher than 25C, cool at 26C, heat at 24C
Relative Humidityminimum 50 and no higher than70%
Carbon Dioxide1500 ppm if the light is available, ambient (~390 ppm) if not
Light17 mol m-2 d-1 combination of solar and supplemental light
Dissolved Oxygen 7 mg/L or ppm, crop failure if less than 3 ppm
pH level5.6-6
EC1150-1250 µS/cm above the source water
Source – Google | Table By – Cornell Controlled Environment Agriculture

Starting Hydroponic Lettuce Seeds

Let’s plant some seeds for the lettuce. You can get good quality lettuce seeds from amazon easily within $6-$10. There are many combos that offer a variety of greens for you to start with. 

If you already have a lettuce crop and want to save some seeds for yourselves then you need to let the plant grow and collect the flower stem after it has seeded. Let it dry in a bucket, shake it into the bucket and then collect what remains. 

Note: Fresh seeds give you a better germination rate, so you don’t have to put too many of them in while planting new crops. 

Now, when you are ready with your seeds, you need to make a little spacing in your grow media, a small divot with the help of a brush or something like that. Once done just put 3-5 seeds into each of your grow cups and then cover the seeds with the media you replaced earlier while making the divot. 

Make sure you don’t compress that coco perlite too much, you want it as loose as possible. Maintain ideal temperature and humidity to get better results.

Making Grow Light Adjustments

Now once the seeds are perfectly placed you need to decide whether you will be using natural light or grow lights? If you are just starting and don’t know much about how to grow hydroponic lettuce at home, I would recommend you go with natural sunlight as that’s the easiest and cheapest option to experiment with. 

You can also use LED grow lights to grow your own hydroponic lettuce at home. This is more preferable when you want to have a controlled environment due to external conditions not being so lovely to support your plant. Lettuce needs at least 12 – 16 hours of daylight, so if you are going with grow lights, keep your timer checked.  

Adding nutrient solution

Now it’s time to add in the hydroponic nutrient. Now again it’s a personal choice to pick which nutrient you want. The most common one is the Flora Grow, Bloom, and Micro fertilizer by General Hydroponics. Easily available and comes in a combo pack so you can use it for all growth stages in hydroponics. 

While we are using the Kratky method to grow hydroponic lettuce, we need something that can sustain on its own without any intervention and it’s well known that green leafy veggies like lettuce grow well in high nitrogen nutrient formula. So, you can use Campbell’s diamond blue or if you are buying from amazon then Easy Peasy urea (46-0-0)  or Down To Earth Organic Meal Fertilizer (12-0-0) are good sources of nutrients for growing hydroponic lettuce at home. 

The rule of thumb is to use 1 gram of nitrogen per 1 litre. So, we are using here 25-litre tub hence 25 grams of

Checking pH and EC level

Most of the beginners either skip this step or feel lazy to do it. But it can be a game-changer. So, you need to have a pH meter to check the pH level of your nutrient solution once you have mixed all things that you want to. 

The ideal pH level for growing lettuce is in the range of 5.5 – 6.5. If in the middle of your growth you see the tips of the leaves are burning that means that the pH level is increasing and you need to re-calibrate it. 

The electrical conductivity levels for leafy greens like lettuce don’t need to be very high. The EC can be in the range of 1.4 – 1.6. That is lower than most other hydroponic crops but it will be enough for lettuce.  

Dropping the Cups

Once you are done with all these steps, the last step is to check whether the nutrient solution is actually at the level that you want. 

For this, you can use an empty cup and put it inside one of the holes. Now you can see if the nutrient solution in the reservoir actually touches the bottom of the net cup. If it does then great otherwise you can add more nutrients to the tub through that net cup itself. This way you will get to know exactly when to stop. 

Once done we are good to go. You can place your home-built hydroponic lettuce system at a good spot and leave it for 30 days at least and see the magic. 

Advantages of Kratky method in growing hydroponic lettuce

So, the Kratky method works in this scenario because it is self-sustainable. Once the seeds germinate they start growing downwards and sidewards. This helps the plant in getting nutrition as the water level drops because the roots are growing along. Not just that, but finer roots grow sidewards (oxygen roots) as well due to the moisture present inside the reservoir. This helps the plants to be well oxygenated. So, some of the advantages are. 

  1. Excellent results
  2. Less effort and easy to use method
  3. Automated supply of nutrients 
  4. High oxygen availability to the roots
  5. Cheaper cost 
  6. Easy Maintenance
  7. No grow lights needed
  8. Repeatable and Replicable
  9. Very less wastage


The Kratky method gives fairly impressive results. So let’s get to the problems.

If you use a grow light that is too far away from the plants then you can see a lot of the lettuce is quite leggy. You need to be really careful with greens and the strength of the lights because you don’t really need that strong of light to get the full growth cycle happening and if you overdo the light you can cause the plant to be stressed and that will, in turn, make the plant bolt so it’s a really fine line when you’re using led lighting or any kind of lighting to grow hydroponic lettuce.

You have to take the inverse square law to take into account which basically means that the amount of light that the plant receives diminishes by the square of the distance from the light which is extremely noticeable when you’re moving an led light fixture up and down in this small distance but when it comes to the sun the distance the plant is growing is insignificant compared to the distance between the earth and the sun.


What to do if the tips of lettuce leaf are getting burned?

You may want to check the pH level of your nutrient solution. This happens when the pH level drops suddenly. So, you can re-balance your pH level by adding more water or nutrient solution to the grow tub. Make sure to check the pH level again in some days.  

How many hydroponic lettuces can I grow in one tub?

It depends on the quantity of the tub. A lettuce crop takes an average of 5-6 litres of space in your tub so keeping that in mind you can plant them accordingly. Keep in mind to space them out quite well, place them at corners of the tub if needed that would give maximum space for the plant to grow. 

How long does hydroponic lettuce take to grow?

Most plants grow faster in a hydroponic system. The romaine and butterhead lettuce take 3-4 weeks to harvest and the iceberg takes six to eight weeks. So, overall the hydroponic lettuce takes 30 days to grow from seed to harvest.

Can I use the same lettuce crops again after harvesting?

Yes, you can re-regrow lettuce after harvesting. Make sure to not cut the roots out. Just add the nutrient and grow media as required and you are ready to start another batch of your favourite lettuce. 

What will happen if I grow Lettuce and Tomato in the same tub?

Lettuce and tomato have different nutrient requirements. While growing both in the same nutrient solution you can experience tomato leaves becoming yellowish on the outer edges and green in the veins. This is due to magnesium deficiency. So, either you can add more magnesium to the solution or harvest the lettuce and balance the hydroponic system for tomatoes only.

If there are more questions which you would like to get answered, then comment down below and I will try to help you as soon as possible. Thank you.