Growing your own hydroponic lettuce allows you to bring fresh, crisp lettuce leaves right to the table, even throughout the chill of the winter months. It’s one of the most popular hydroponic crops to grow, and for good reason.
So without further delay, let’s jump into the most comprehensive hydroponic lettuce guide on the web!
Table of Contents
Lettuce Overview
| Scientific Name | Lactuca sativa |
| Common Name | Lettuce |
| Genus | Lactuca |
| Family | Asteraceae |
| Origin | Ancient Eygpt! |
| Size and Dimensions (Mature) | Between 15 – 50cm (12-20 inches) tall. Often sprawls equal to height. |
| Distinguishing Features | Edible leaves in green or red |
The Basics of Hydroponic Gardening
Hydroponic gardening is the cultivation of plants and crops in nutrient-dense water without the use of soil. All you need are plants, some nutrient-rich water, and somewhere for them to grow!
Some hydroponics systems are no more complex than a large tank with plants floating above the water on rafts. Others are technological marvels that actively monitor water flow, temperature, and acidity, ready to adjust essential elements as needed.
Different Types of Hydroponic Systems for Lettuce
We’ve come a long way since growing lettuce in ancient Egypt. Now, we have some incredible technology at our fingertips, and the hydroponic wonders just keep coming!
Just as there are different garden ideas like a movable garden, chaos garden, or formal garden to plant our plants, hydroponic also comes with different choices of systems to plan our garden.
Here are a few different types of hydroponic systems that can be used to grow your own lettuce.
For some quick info, we typically choose deep water culture systems as the best hydroponic system for lettuce.
Deep Water Culture
Lettuce is ideal for Deep Water Culture systems. In deep water culture systems, lettuce is grown in net pots as a growing media. The base of the plants rest directly in a tank of nutrient-rich water, with the roots below the water level.
A Deep Water system can be active or passive.
Passive systems don’t need an air or water pump and are often pretty straightforward to run.
The best passive Deep Water technique for lettuce is the Kratky system. It’s tailored to meet specific needs and is fantastic for first-time growers and veteran gardeners alike.
An active Deep Water Culture system uses electric pumps to circulate the nutrient solution and air stones or air pumps for oxygenation.
The popular Aerogarden systems are active. They’re pricey but very effective.
Nutrient Film Technique
In Nutrient Film Technique systems (NFT Systems), the lettuce rests in a net pot above a channel. It’s gently sloped, and when the nutrient solution is pumped to the upper end, it flows through the root system and out the bottom.
An NFT system is complex. The pumps are critical to keeping your lettuce hydrated; if they fail, it doesn’t take long for the entire plant to suffer.
You also need to filter and provide artificial aeration. The payoff is greater productivity in even a small space.
Wicking Beds
Wicking beds are a relaxed first step into hydroponics. Lettuce is grown in a shallow bed of soil-free medium. The nutrient solution sits below, and a series of wicks run deep into the growing medium from the bottom of the reservoir tank.
Through the power of capillary action, the wicks draw the liquid from the reserve into the medium. Air stones or aeration pumps in the tank provide oxygen, but otherwise, this is very low-tech.
It does have limits to its scale, but for most home growers, it’s one of the best options. The medium stays moist and well-nourished with little effort.
Drip Irrigation System (Dutch Bucket)
Drip irrigation system hydroponics uses freestanding containers to hold plants. Buckets are most common, hence its other name.
In this system, pipes drip precise measurements of nutrient solution into the containers. Timers ensure the medium remains moist without over-watering.
It can be tricky to organize all those timers, pumps, and miles of plastic tubing to perfection. That said, the Dutch bucket is the most effective method for large crops. This is the system for you if you’re after a full-sized head of lettuce.
What You Need to Grow Hydroponic Lettuce
To grow a basic hydroponic lettuce garden, you will always need:
- Lettuce seeds or seedlings
- Growing medium
- Nutrient solution
- Container for medium
- Nutrient tank
- Air pump or stone
- Thermometer
- Electrical Conductivity and pH monitor
From there, different systems need different things. Most rigs also require grow lights to provide enough hours of light. Active systems need circulation pumps and filters. Drip Systems need plastic pipes, timers, and drip heads. NFT needs channels, and wick systems need wicks!
Key Considerations for Growing Hydroponic Lettuce
Space
How much room do you have for your setup? Most varieties of lettuce grow well close together and don’t need big rigs. It’s also easy to scale up for a larger harvest.
Budget
This is not an expensive plant to grow. Lettuce grows just as well in a passive setup made from a recycled plastic container as in a larger, more expensive setup. Their low nutrient intake means they thrive on low-cost blends designed for leafy greens, further cutting back your outlay.
Time Available
Most lettuce varieties only take 50 to 60 days to mature. You also don’t need to set much time aside to tend to them.
Light
While grow lights are common for lettuce hydroponics, it’s not always needed. Depending on your local conditions, it’s totally possible to grow outdoors in direct sunlight. In fact, the hydroponic Salad Table system developed at the University of Minnesota was designed with just such a use in mind.
For the rest of us, a grow light – either low-wattage LEDs, fluorescent lighting, or specialist metal halide lights – will do the job.
However, some studies have shown that hydroponic lettuce production with fluorescent lights uses significantly more hydroponic nutrient solution than lettuce grown under LED lights.
Best Types of Lettuce for Hydroponic Systems
Let’s take a look at some of the best lettuce for hydroponic systems.
Romaine Lettuce
The Little Gem variety of Romaine is ideal for hydro. It only reaches a height of around 6 inches (15cm) and has sweet leaves. They fit nicely in even compact systems.
Loose Leaf Lettuce
Ruby is my go-to loose-leaf variety. It has glorious color and matures quickly. It also has no issue at all being harvested one leaf at a time.
Butterhead Lettuce
Bibb lettuce is a real winner. While it takes around two months to mature, the outer leaves can be eaten much earlier. It’s heat tolerant and has a good margin of error for beginner gardeners.
Iceberg Lettuce
The European Style Batavia is another good choice. It’s hardy and rarely bolts in higher temperatures. Choose between green- or red-leafed varieties for a pop of color in your harvest.
How to Start Hydroponic Lettuce
What You need:
- Lettuce Seeds
- Clean Water
- Soil-Free Seed-Raising Medium
- Propagation Tray or Shallow Container with Transparent Lid
From Seed
How to Start Hydroponic Lettuce from Seed:
- Moisten your seed-raising medium thoroughly with plain water and place it in your tray.
- Sprinkle seeds across the surface and cover to a depth of about a quarter inch (half a centimeter).
- Close the lid and place it in a cool, well-lit area. They won’t germinate readily if kept above 75°F (24°C).
- It will take a week or two for the seeds to sprout. Keep the medium moist and the container well-lit. Once the seedlings have their first true leaves, you can transplant them to your hydroponic system, as outlined below.
Transplant
How to Transplant Lettuce Seedlings into Your Hydroponic System:
- Prepare the growth medium used in your system. For most, this means soaking overnight in plain water. If using Rockwool cubes, check the pH level. If using coco coir, check the EC as it is sometimes salty.
- Place your medium into position in its bed, bucket, or net pot.
- Take your seedling and wash its roots. For commercial seedlings, ensure all dirt is completely removed.
- Carefully plant the seedling into the medium.
- Place the container in the system.
Potted Exotics Pro Tip: An egg carton makes a great, low-cost seedling starter for lettuce and is a popular option for many hydroponic lettuce growers!
Hydroponic Lettuce Care and Growing Conditions
With the right care and growing conditions, growing hydroponic lettuce is a breeze, and it’s one of the best ways to take part in sustainable agriculture!
Nutrient Solution
Give your lettuce a nutrient solution that is mildly acidic and not too rich. Aim for a pH between 6.0 and 6.4 and an electrical conductivity of around 1.4 to 1.8.
Nitrogen and calcium are both essential nutrients for lettuce, so you should aim for a nutrient solution with higher calcium levels. Tap water has very little calcium, so you need to introduce larger amounts.
Shoot to create a water solution with around 130 ppm of calcium for best results. Tap water has very little calcium in it, so you really need to introduce larger amounts.
Be sure to buy a reliable pH test kit so that you can monitor your hydroponic water closely.
Temperature
Lettuce is listed among cool weather crops, so prevent them from overheating. Cooler temperatures prevent bolting and keep them from developing a bitter taste. In outdoor hydroponic systems, the summer months can be too hot for most lettuce varieties, especially without sufficient shade cover.
Aim for an air temperature of between 16 to 18°C (61 to 64°F) for best results, but they tolerate up to 24°C (75°F).
Light
Lettuce will grow with as little as 10 hours of light a day, though for bumper harvests, between 12-14 hours is better.
Some varieties, like Muir, enjoy long days of 16 hours or more, so be mindful when picking between different varieties. Too much light causes deformed leaves, so it pays to be careful.
For indoor hydroponic systems, be sure to choose grow lights that don’t give off too much heat. An LED grow light is ideal and is considered one of the best grow lights for lettuce. LED light is sufficient but doesn’t give off too much intense light.
Humidity
Relative humidity between 50 and 70% with good air circulation is best. Too little humidity and you risk leaf burn. Too high humidity leads to leaf issues.
How to Harvest Hydroponic Lettuce
To harvest a head, you only need to remove it from the system and chop free the roots. Simple!
“Cut and come again” harvest is even easier. Just remove the outer leaves, and they’re ready to wash and eat. It’s the best way to have fresh lettuce every time.
Hydroponic Lettuce Problems
As with any plant, hydroponic lettuce is susceptible to certain pests and diseases, and you should keep a close eye and watch for signs of the following.
Flying Insects
Cabbage moths, grasshoppers, and cutworms love lettuce, especially young plants.
When growing outdoors, watch for nibble marks or eggs. You can remove them by hand, but most commercial pesticides work fine too.
A teaspoon of Castille soap in a half gallon of water also makes for serviceable low-chemical bug spray.
Getting your lettuce indoors helps immensely. I love watching moths beat at the windows of my growing area, safely separated from my crops by thick glass.
Tip Burn
Tip burn is the most common problem with lettuce plants in hydroponics. Older leaves develop a crispy brown edge that resembles a burn.
It’s caused by strong nutrient solution, and hot weather and low humidity make it worse.
Check your solution and dilute as needed with fresh water. Those outer leaves won’t heal but can be eaten as usual.
Root Problems
All hydroponics requires you to monitor the roots for signs of disease. If aeration is poor, fungal diseases move in.
It’s hard to shift once established, and even professional greenhouse lettuce growers lose whole crops to root disease.
Keen your nutrient solution mildly acidic to prevent drama. There’s research to suggest a mild hydrogen peroxide solution flushed through the system is effective at killing off the pathogens. However, it’s usually best to turf the lot and start again for a crop like lettuce.
Frequently Asked Questions About Hydroponic Lettuce
Can You Grow Lettuce Hydroponically?
Lettuce is one of the easiest crops to grow hydroponically. It thrives in many different hydroponic systems and will produce crops in as little as a few weeks.
How Long Does it Take to Grow Lettuce Hydroponically?
Some varieties of lettuce take only a few weeks to be ready for harvest. Others can take three or more months.
The good news is that you can clip mature leaves much sooner and leave the rest of the plant to keep growing. This is called “cut and come again” and is a great way to harvest small amounts at a time.
Is Hydroponic Lettuce Healthy?
Hydroponic lettuce is precisely as healthy as that grown in the field. It’s no superfood, but it does contain a lot of dietary fiber, Vitamin C, and iron.
Does Hydroponic Lettuce Taste Better?
The most important thing for taste is the type of lettuce, not how it was grown. The care the plants receive matters too.
For lettuce, that means keeping it at the best temperature and fertilizing well. Do it right, and hydro or field lettuce will taste equally good.
What Lettuce is Best for Hydroponics?
I love compact cultivars for hydroponics. The Mini Gem and Buttercrunch varieties are perfect for all types of hydroponics. They are small and mature in a way that allows for “cut and come again” harvest.
How long Does Hydroponic Lettuce Last?
The most wonderful thing about hydroponic lettuce is that if you leave it in the system, it will last for months. It beats refrigeration and produces fresh leaves every harvest.
Do I Need to Wash Hydroponic Lettuce?
Always wash your crops before you eat them. Even plants grown indoors in perfect conditions wind up with dust on their leaves. It’s worth the time.
Are there Disadvantages to Growing Lettuce Hydroponically?
Hydroponics isn’t for everyone. You need to have the space and money to invest in the system. It’s also very easy for things to go wrong.
Fungal diseases love getting into roots and devouring your crops whole. You also have to monitor constantly.
Thankfully lettuce is just about the easiest vegetable to grow in hydroponics. For most, the advantages far outstrip the risks.