Being a relatively low-maintenance crop means that lettuce is one of the most popular vegetables for hydroponic growing.
Lettuce is a cool-weather crop. If temperatures get too warm, meaning above 77°F, this stimulates the plant into producing flowers, which means that the leaves will no longer taste very nice. Not only will they be more bitter, but their texture will also be tougher and more fibrous.
However, if temperatures are too cool, growth will be stunted and your plants won’t be very productive. This makes it important to maintain ideal temperature ranges when growing lettuce hydroponically.
For most varieties, this means a daytime temperature of around 50°F to 75°F. Just like most plants, lettuce benefits from a slight temperature drop at night, with an ideal night time temperature being between 40°F to 60°F.
It’s not just ambient temperature that matters. You need to keep the temperature of your nutrient solution consistent too in order for your lettuce plants to properly grow.
A water temperature of between 68°F to 77°F is ideal.
If you let your water temperature run too hot, the water won’t be able to hold enough oxygen. However, allowing it to drop too low will slow down plant growth, making it important to maintain your water temperature at optimum levels.
You may think that the more light your lettuce plants receive, the better, but this isn’t the case.
Too much light will make those lettuce leaves taste bitter. It also means that your plants will flower faster, which means that they have come to an end.
Ideally, your lettuce plants should be receiving about 10 to 14 hours of medium-bright light a day.
If you’re growing red-colored lettuces, there’s one more thing to keep in mind. The plants will stop producing anthocyanin, which is the pigment that gives the lettuce its distinct red hue, if they aren’t receiving enough light. It may take some trial and error to find the perfect light/dark balance.
The best pH level for growing lettuces hydroponically is between 5.5 and 6.5.
Although lettuces are tolerant of slight pH fluctuations, you should still try to maintain a consistent pH level for maximum harvests.
While many crops need to grow flowers in order to produce fruits, lettuces are grown for their leaves.
This means that they don’t need as much potassium as other plants, since potassium is a key player when it comes to fruit production.
Instead, lettuces need more nitrogen and phosphorus. Look for a nutrient solution that focuses on foliage rather than flowers.
Many growers will also add extra calcium nitrate and Epsom salt to their nutrient solution, since these aren’t usually included in pre-made hydroponic nutrient formulas. Lettuces are prone to calcium and magnesium deficiencies, and this helps to prevent that. If you notice yellowing leaves on your plants, then this is a sign of a deficiency.
Lettuce is extremely adaptable when it comes to growing mediums. This means that you can pick the growing medium that best suits your specific hydroponic system.
Some of the most popular choices for growing lettuces are:
In some hydroponic systems, your lettuce won’t need any sort of growing medium.
The way in which lettuces are so shallow-rooted is what makes them so well-suited for hydroponic growing.
This means that their growing area doesn’t need to be very deep.
The compact size of most lettuce varieties also means that you can fit several plants into a small space. This makes them the ideal crop for those who want to grow their own food in their home.
About 6 inches of space is usually enough for a loose leaf lettuce. Varieties that form a head will need a little more room, 10-12 inches works well.
While just about every variety of lettuce can be grown hydroponically, there are some that are better suited to hydroponic growing than others.
There are 2 main types of lettuces out there:
- Loose leaf lettuces
- Lettuces that form a head
Loose leaf lettuce varieties tend to be preferred by hydroponic growers. This is simply down to the fact that they can be harvested over a longer period of time and are ready for harvest much sooner.
They also take up less space in a hydroponic system than lettuces that form heads, meaning that you can fit more plants into your growing area. This then allows you to grow a greater variety of different lettuces.
Let’s learn how to grow hydroponic lettuce indoors:
There are several different types of hydroponic systems out there, and lettuces can be grown in just about every single one of them.
However, some are designed for heavy feeders, meaning that they contain a number of features that aren’t required for growing lettuce.
It’s likely that you want to keep things as simple and low-maintenance as possible. So, these are some of the best hydroponic systems for growing lettuce:
If you’ve been researching hydroponic lettuces, then you’ve probably come across the term “lettuce raft” before. This is a form of a deep water culture (DWC) system.
It basically consists of filling a container with a nutrient solution and then floating your lettuce plants in a “raft” over the top of this. Since lettuce has shallow roots, the container you use only needs to be a few inches deep, making this system great for small spaces.
While a DWC system does require the use of pumps, it’s pretty low-maintenance once you’ve got things set up. Fluctuations in temperature, pH, and nutrients are minimal, making this an easy system to maintain.
Alternatively, look into the Kratky Method, which is a variation of the standard DWC system. This system is completely passive, meaning that it doesn’t require pumps. Although yields are lower when compared to classic DWC systems, they are still fantastic for growing lettuce hydroponically.
In a nutrient film technique (NFT) system, your lettuce plants sit at the top of long growing chambers, with their roots dangling down into the chamber.
A nutrient-rich water is then pumped through the chambers at regular intervals. As the water moves through the chamber, it feeds and nourishes your lettuce plants.
Again, because lettuce plants are so shallow-rooted, the growing chambers don’t need to be very deep.
Growing lettuce in a NFT system also means that you can make use of vertical gardening techniques. This allows you to fit more plants into a small space.
Ebb and flow systems see your lettuce plants growing in trays, either directly in the trays themselves or in pots that sit in those trays.
The trays are connected to a reservoir that sends a nutrient-rich water up at periodic intervals, which floods the growing trays. This feeds your lettuce plants.
Excess water then drains away back into the reservoir, ready to be used again.
A grow tent is a compact tent that is lightproof and waterproof. They are designed to provide a controlled growing area for those who want to grow hydroponically.
Grow tents are great for maximum accuracy when it comes to growing conditions. Growing your lettuce in a contained area makes it easy to keep temperature, humidity, and light consistent, which is exactly what your lettuce plants need in order to thrive.
However, the downside to a grow tent is that they make the growing process a bit more costly.
Not only will you need to purchase the tent itself, but you will also need to use grow lights. Of course, lettuce doesn’t need a huge amount of light, meaning that you could get away with fluorescents, but that’s still an extra investment.
Fans to provide additional ventilation may also be required. Some hydroponic systems, especially those that use larger pumps, can run a little hot, making fans vital for keeping temperatures down.
While grow tents do usually mean that you will enjoy a bigger harvest from your lettuce plants, they aren’t a must.
A simple hydroponic system can easily be set up on a sunny windowsill, and this will give your plants all of the light they need in the warmer months of the year.
However, a windowsill can limit light in the winter months, making a grow tent a good option for those who want to enjoy maximum yields throughout the year.
Lettuces aren’t demanding, making them one of the easiest crops to grow hydroponically.
Even better, once you have everything set up, your lettuces will be ready to harvest in just a few weeks, making hydroponic lettuce the way forward for those who want a fresh source of salad throughout the year.