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Measuring Hydroponic Lettuce Spacing for Optimal Growth

    There are several factors that affect the growth and yield of hydroponic lettuce. But if the spacing between the plants is not right, whatever you do is not enough. You need to get the hydroponic lettuce spacing right if you want to ensure optimum growth. 

    For any lettuce, spacing depends on the head size of fully grown lettuce.

    The average size of the head of lettuce is 30 cm, but it varies depending on the variety. You should keep the spacing for hydroponic lettuce 30 cm and above. 

    In this post, I will help you understand how spacing affects the yield, how to find the spacing requirement, and also the spacing for different varieties of lettuce. 

    Effect of Hydroponic Lettuce Spacing

    Let’s understand how spacing affects the lettuce crop so that you can optimize your hydroponic system for your needs. 


    The first effect of spacing you will observe is the height of the crop. I have tested it many times to see how the crop reacts when planted closely and far. 

    I observed that when plants are closely placed, they tend to grow taller compared to crops placed closely. So I looked for the reason for it. 

    I found a scientific paper published by the Department of Horticulture, Sher-e-Bangla Agriculture University, Bangladesh.  The same was observed in the experiment.

    According to the experiment, when the crop is placed closer to each other, they tend to compete for the light. As a result, they grow taller to capture the maximum light. 

    Leaf Yield

    For lettuce, yield means a well-developed and a high number of leaves. And spacing affects how the leaves of lettuce develop in a hydroponic system. But in the case of leaves, there is an optimum range that you have to maintain. You cannot keep them too close or too far. 

    According to a research article released by Beyenesh Zemichael of Tigray Agricultural Research Institute, Mekelle Agricultural Research Center, Ethiopia, the optimum distance you have to keep for hydroponic lettuce is between 30-60 cm. 

    Also, according to the paper, the highest leaf number was observed when the lettuce crop was placed under  60 cm. 

    And when you increase the space between the plants up to 70 cm, you may observe the width of the leaves is higher. But the total biomass of the yield is much lower compared to 60 cm spacing.  

    In addition to that, I feel, increasing the space will also decrease the profitability because the yield per square ft will decrease. This is not good for commercial setup. 

    A lot of the weight of the lettuce comes from its leaves. So I suggest for optimum growth of the lettuce leaves, you must keep the interspacing between 30 to 60 cm. Going beyond that reduces the overall mass of the plant, even if the lettuce has longer leaves. 


    As for the root length is concerned, the more space you leave between the two lettuce crops, the more widespread the roots grow. Even the mass of the roots is much higher. 

    I observed that at least 30 cm is needed for lettuce to have optimum root growth. 

    If you leave the space less than that root length is shorter, which directly affects the vegetative growth of the hydroponic lettuce. 

    How To Measure the Hydroponic Lettuce spacing?

    It is recommended to have a hydroponic lettuce spacing of at least 30 cm and beyond, but you must have your own reference. The reason being there is a variety of lettuce, and there are other factors like nutrients, etc which affect the growth of the plant. 
    So here I am giving you a step-by-step guide to you identify the optimum hydroponic lettuce spacing. 

    Plant Sample Lettuce

    First, take the variety you plan to grow in bulk. In order to get the idea of spacing, you must grow a few sample plants of lettuce. I suggest growing at least 10 plants for the best result. Put them in separate pods. Here you don’t have to keep them in the tray. Keep them separate. So that they can grow without any competition. 

    Go Through the Growth Cycle

    Use the same hydroponic system that you want to use for growing lettuce. Add the same nutrients and also set the same conditions. For best results, use the same source of water too. Throughout the growth cycle of the plant, do the same things that you plan to do when growing in bulk. Use the same schedule of ppm adjustment, tank cleaning, pH adjustment, etc. 

    Measure the Head Diameter

    hydroponic lettuce spacing measurement

    At the end of the growth cycle, when the lettuce is ready for harvest, start measuring the plant. I recommend getting a 60-centimeter scale. You have to measure two things to get the best idea about spacing for the hydroponic lettuce. 
    – Headsize
    – Plant Height
    For the measurement of head size, keep your scale in the center of the lettuce head and see what is the diameter of the head. Follow this schematic for a better idea. 

    Measure the Height

    hydroponic lettuce spacing measurement

    In order to measure the height of the plant, remove the plant from the pod and lay it on a piece of paper or anything with white background. Using a pencil, mark the point from where the root and stem separate and also mark the tallest leaf of the lettuce. Now using a scale, just measure the distance between the two marks to get the idea. Look at the picture for a better idea. 

    Calculate the average spacing measurement

    Now take the measure of all the 10 sample lettuce plants that you have grown to get the idea of average diameter and height. Just add the diameters of all 10 plants and divide it by 10. Do the same for the height. Whatever average diameter you get used it as the spacing benchmark when placing the pods in your hydroponic system.  

    Also, Take Look At Our Top Hydroponic System For Lettuce

    Spacing for Different Varieties of Lettuce

    Here are some of the measurements of hydroponic lettuce spacing that I have on varieties of lettuce:

    Lettuce VarietySpacing (in centimeters)

    Final Thought

    When you do it a couple of times, you won’t have to go through the process again. You can follow the same hydroponic lettuce spacing measurements every time you grow the same variety of lettuce. I recommend you keep a chart that keeps a record of this measurement for every plant that you grow in a hydroponic system. 

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