Nutrient Guide: How to Grow Lettuce Hydroponically

Introduction

Lettuce is arguably the most common pick for hydroponic beginners due to their low maintenance and high yields.  Not only is it suitable to grow all year round, but it also takes a mere three weeks to experience the first harvest. On top of that, it does not need complete sunshine and can even thrive in an environment with scarce light and low temperatures. Its flexibility is also further pronounced when we consider the fact that its nutrient mix is rather simple to prepare and does not require any changes over the course of its growth. If you are interested to procure your own hydroponic-grown lettuce, do read on to better prepare yourself for what’s to come.

Choosing the type of lettuce   

Although most conventional lettuces are suitable to be grown in a common hydroponic setup, one can enjoy greater flexibility and prolonged harvest of their yields with loose lettuce varieties. Leaves of this specific variety of lettuces can be harvested individually, and they will grow back and replenish themselves over the season. These are some of the popular lettuce varieties for your consideration:

The butterhead lettuce comes in two variants: the Boston lettuce, and bibb lettuce. The former resembles a rose flower that has a bulbous and head-like figure, while the latter is easily spotted with its smaller head which bears resemblance to a cup. Both variants can be harvested by individual leaves or as a whole.

Commonly seen in the classic caesar salad, the romaine lettuce is another highly favored choice by the masses.  Do take note that there are different variants of this type of lettuce available, which may alter the shape of its head.

Lastly, the loose-leaf lettuce is a variant where the crop does not form a head, and leaves are held together by its stem. The oak leaf cultivar is one of the most sought-after choices for homegrown gardeners to grow.  

Before we move on, the lettuce comes in multiple countless cultivars that vary in colors and flavors, which we highly recommend those interested in trying to grow all the different varieties. 

Growing Requirements

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While lettuces are generally easy to grow, it is necessary for one to do their due diligence as well.

Lettuces grow better in lower temperatures. The ideal range of day and night temperatures is between 68 to 75 Fahrenheit and between 60 to 65 Fahrenheit respectively. 

For electrical conductivity (EC), we recommend a value of around 1.4mS/cm. A growing medium with a pH of around 5.5 to 6.0 would be optimal for hydroponic lettuce. 

To aid proper growth of the lettuce, give it some mid or low light for about 10 to 14 hours would be sufficient. Try to avoid the full sun as they can result in bitter-tasting lettuce leaves. For those who are all about the little details,  the optimal daily light integral (DLI) requirement of butterhead lettuce is 17.1 mol·m–2·d–1.  Another interesting note is that light quality does play a part in red-leaf varieties. Those cultivating red variants should make sure that they have the equipment to provide the necessary lighting. 

Additionally, one should prepare a solid growing medium and a nutrient solution. The solid growing medium is actually there to help the seedling germinate and acts as a support for the plants as it grows. We recommend stone wool and phenolic foam.

The water nutrient solution should be one with an N-P-K ratio, where N means nitrogen, P means phosphorus, and K refers to potassium. Nitrogen should be highest in the concentration and potassium the least. We recommend adding micronutrients and having sufficient calcium generally. Last but not least, it is good practice to aerate the solution sufficiently. A good gauge of this would be maintaining a dissolved oxygen concentration of around eight ppm. 

Regarding the growth period, expect loose leaves variants to typically take 40 to 45 days, and those tighter head variants to take longer at 80 to 85 days.

Now that we have gone over the preparation details, it is time to discuss the methods and hydroponic systems used to cultivate lettuce. Most massive and commercial growing utilize the Deep Water Culture and Nutrient-Film Technique. 

In Deep Water Culture, growers use a pond culture, which holds a large amount of nutrient solution. Its greatest strength lies in the generous amount of solution needed for the process, which actually, in turn, helps to regulate temperature and prevent drastic and unwanted changes in the optimal growing conditions.  Conversely, the main point of the Nutrient-film technique is its use of nutrients in the shallow channels of the root zone in the form of a thin film, which is circulated at a constant rate. 

For most home-grown growers, we would recommend these simpler systems which are less tricky to set up and operate.

First off, we have the Ebb & Flow system, also known as Flood or Drain systems. The growing medium and root zone are constantly flooded with the nutrient solution, which is then drained back into the reservoir. Both actions do not happen simultaneously and occur after each other.

The other recommended method is the Krafty method. It is a subset of Deep Water Culture, which does not rely on water pumps or electricity to channel nutrients to the roots. The Krafty is by far the simplest yet most efficient method favored by most home-based lettuce growers.

In Conclusion

Simplified Hydroponics

Lettuce is the best option for anyone interested in hydroponic growing to familiarize themselves with the complexities and rekindle their love for this hobby. It is definitely the easiest and most flexible plant to grow compared to the multiple offerings out there, and it is suitable as a beginner plant for hydroponic starters. They are not time-consuming to cultivate and can be cultivated across multiple types of hydroponic systems. Even the simple Krafty method will work fine for the lettuce crop. 

However, this is not to say that lettuce is not a crop for seasoned growers. In fact, the lettuce crop is a great option to test out new and different hydroponic options, or for those looking to expand their growing scale. To add on, lettuce crops also sell decently well and can definitely turn into a side job for those of you looking for some extra cash on the side.

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