Whether growing for your market garden or your own benefit, nothing beats the fresh crunch of hydroponic lettuce. This kitchen favorite goes well in salads, burgers, wraps, and more and is simple to grow from seed or seedling.
Lettuce thrives in a hydroponic environment. Hydroponic systems naturally provide conditions that keep their roots ideally moist but not too wet and stave off many of the pests and diseases that traditional soil-based gardeners face. Plus, it grows fast – that makes it an ideal choice for beginners just dipping their toes into hydroponics, with an almost guaranteed yield in just over a month that’s sure to inspire you to keep growing!
The Benefits of Growing Lettuce Hydroponically
This versatile veggie does exceptionally well in hydroponic conditions. Researchers have found that hydroponic lettuce holds its own against conventionally grown lettuce in terms of odor, taste, texture, and visual quality.
And there are a whole host of reasons to grow your lettuce hydroponically:
- Grow lettuce year-round: lettuce is usually a cold season crop that bolts and goes bitter quickly in hot weather. By carefully controlling the conditions your lettuce grows in, you can enjoy lettuce all year round.
- More energy where it matters: growing to gather oxygen, water, and nutrients from soil takes up the lettuce’s valuable energy. By growing it in a soilless medium, more of the plant’s energy can be devoted to growing the green leaves we want to eat.
- Take up less space: hydroponic gardening takes less space than traditional soil gardening. By providing your lettuce with nutrients in the water, they don’t need to reach as wide with their roots and can grow happy and healthy in a smaller area.
- Fewer pests: many of the pests and diseases that harm lettuce harvests are soil-borne. By growing without soil, you can avoid a lot of these challenges.
- Gain more control: hydroponic setups give you more control over your garden than traditional, outdoor growing. Once you’ve optimized the conditions for your lettuce, you can enjoy a reliable yield.
How to Grow Hydroponic Lettuce
Lettuce is a beginner-friendly hydroponic crop that will reward you with delicious crunchy greens in just over a month. Create the ideal conditions for your hydroponic lettuce for a bountiful harvest:
Light
Most varieties of lettuce are happiest in moderate to low light conditions. Too much light can cause slower growth, bitter leaves, burnt leaf edges (also known as tipburn), and bolting. Choose lower wattage to grow lights to protect those tender leaves, and don’t place the lights too close to your plants.
When starting from seed, give your little lettuces between 14 and 16 hours of low to moderate light each day. Once your seedlings sprout, switch the lighting to around 12 hours daily and monitor the plants closely to see if you should make further adjustments. Look out for muted colors, indicating that your plants want more light.
Water
Lettuce loves water! It’s essential to keep your lettuces moist but not drenched, so they do well in hydroponic systems.
Replace your water solution every two or three weeks.
Temperature
Lettuce is a cool-season crop – too much heat can cause the lettuce to grow bitter or bolt. Keep your hydroponic lettuce between 68- and 75-degrees Fahrenheit during the day and between 60- and 65-degrees Fahrenheit at night.
Humidity
The ideal humidity for hydroponic lettuce is 50%, so you should aim to keep your garden between 40 and 70 percent humidity.
Too much humidity can promote unwanted fungal growth on the lettuce heads.
Growing Medium
Lettuce does exceptionally well in the soilless growing mediums used in hydroponics and does best with good drainage to keep its shallow roots moist but not too wet. Popular choices include:
- Rockwool (also known as stone wool)
- Phenolic foam
- Coco Coir
- Peat moss
- Perlite
- Vermiculite
- Mixtures including any of the above
Spacing
The spacing your lettuce needs will vary depending on the variety you choose, but will range from around 6 inches apart for loose-leaf varieties to 12 inches apart for those with firm heads.
pH
The best pH for hydroponic lettuce is between 5.5 and 6.5.
Nutrients
The nutritional needs of hydroponic lettuce are simple and can be kept the same throughout its lifecycle since we eat its leaves and not the flower.
You should provide your hydroponic lettuce with:
- Nitrogen: lettuce craves ample nitrogen to stimulate plenty of leafy growth. Experienced hydroponic gardeners recommend including nitrogen around 5 (e.g., a nutrient solution of NPK 5-10-15). If your lettuce isn’t getting enough nitrogen, its roots will shrink, and it will eventually yellow.
- Phosphorus: phosphorus helps your lettuce reach maturity quickly. You should provide it at a level between 15 and 20 (e.g., a nutrient solution of NPK 5-18-20). If your lettuce doesn’t get enough phosphorus, its leaves will first turn dark green, then red or purple, and the leaves will deform.
- Potassium: for big healthy lettuce leaves, your plants need potassium. Provide it in the range of 20 to 40 (e.g., a nutrient solution with NPK 8-10-38). Your lettuce leaves will wilt, become spotty, and darken without enough potassium.
- Calcium: calcium helps lettuce avoid tipburn and grow crispy leaves. Your nutrient solution’s PPM (parts per million) should be between 100 and 150 (15-0-0 NPK). Without adequate calcium, you’ll observe darker, wavier lettuce with tipburn.
- Magnesium: magnesium activates certain enzymes inside the lettuce that are crucial to healthy growth. You should add about a quarter teaspoon of pure magnesium to your solution and look out for yellow “bleeding” on leaf tips that might indicate your lettuce needs more.
- Other Micronutrients: your hydroponic lettuce will also benefit from boron, chlorine, copper, iron, manganese, molybdenum, nickel, and zinc.
You should replace your nutrient solutions every two to three weeks.
Pruning
Lettuce doesn’t require pruning unless you notice disease or damage. If you see signs of either, trim off the affected areas.
Harvesting
One of the best aspects of growing lettuce is that you can harvest as much or as little as you want to eat at any time! Once your lettuce is mature (at about 6-10 weeks, depending on the variety you chose), you can either:
- Cut-and-Come-Again: this is a popular harvesting technique for home gardeners growing loose-leaf varieties and works precisely as it sounds. Once the outer lettuce leaves are about 4 inches long, cut them off, leaving the center of the plant intact. Your lettuce will keep growing, allowing you to come back again and again for a continuous harvest.
- Whole Head Harvesting: many crisphead and iceberg varieties are best when harvested all at once. To do this, check your seed packet or the guide above to determine when your plant will reach maturity and the ideal flavor. The center of the head should feel firm and compact, but the outer leaves should not yet have turned brown. Cut the head about 1 inch above the roots if you want to preserve the crown for a second harvest, or dig it up from the roots if you’re ready to grow something new in its place.
Storage
Your fresh hydroponic lettuce will taste its best as soon as you harvest it, but you can store it in the fridge if you have more than you can eat right now. Loose leaves last up to three days, but whole heads will last up to two weeks.
After washing harvested lettuce leaves, wrap them in a towel or coffee filter to absorb any excess moisture. Change the towel anytime it gets too soggy. Alternatively, if you harvested the whole lettuce head, you can place it in a bowl of water.
The best place in the fridge for lettuce is the crisper drawer. Keep your lettuce away from the frosty back of the fridge and away from apples, bananas, and pears which could speed up withering and decomposition.
You can give your lettuce a little added crunch by putting it in an ice bath for 15 minutes before serving it.
Best Types of Lettuce for Hydroponic Gardens
You can grow any variety of lettuce in your hydroponic garden. If you garden purely for enjoyment, it doesn’t matter which you choose – feel free to explore any varieties that appeal to you! But if you’re looking for more reliable, fast growth to feed your family or for the market, here are the nine best lettuce varieties to choose from for your hydroponic garden:
Salad Bowl Lettuce
Type: Loose Leaf
Time to Maturity: 40 – 50 days
Best for: rapid growth
Best way to harvest: cut-and-come-again
Salad Bowl lettuce is an oak-leafed heirloom variety that matures in as little as 40 days when grown hydroponically. It is tender, sweet, and prolific. Salad bowl is an excellent choice if you’d like to enjoy a quick and crowd-pleasing harvest. If you’re new to growing hydroponic lettuce, this is a great variety to start with.
Grand Rapids Lettuce
Type: Loose Leaf
Time to Maturity: 45 – 60 days
Best for: tipburn resistance and low light conditions
Best way to harvest: cut-and-come-again
Grand Rapids lettuce is tipburn-resistant, which helps overcome a common issue faced by many hydroponic lettuce growers where the edges of lettuce leaves dry up and brown under the grow lights. Grand Rapids lettuce also does very well in lower light conditions, so you can use less powerful grow lights.
Parris Island Cos Lettuce
Type: Romaine / Cos
Time to Maturity: 55 – 75 days
Best for: staying sweet
Best way to harvest: cut-and-come-again
Parris Island Cos is a short, reliable, and mildly flavored variety that maintains its sweetness longer than other varieties (which can quickly turn bitter if not harvested at the right time).
Buttercrunch Lettuce
Type: Butterhead / Bibb
Time to Maturity: 60 – 70 days
Best for: whole-head harvesting
Best way to harvest: the whole head
With its soft, buttery texture, Buttercrunch is a favorite for a good reason. It’s better for those who’d like to harvest whole heads rather than the cut-and-come-again approach.
Rouge d’Hiver Lettuce
Type: Romaine / Cos
Time to Maturity: 50 – 60 days
Best for: stunning color
Best way to harvest: cut-and-come-again
The gorgeous burgundy red of these lettuce leaves deepens in colder weather. It thrives in hydroponic systems, making it a fantastic choice to add some color variety to your salad mix.
Hanson Improved Crisphead Lettuce
Type: Iceberg / Crisphead
Time to Maturity: 70 – 80 days
Best for: great iceberg type
Best way to harvest: the whole head
Crisp and tasty, the Hanson Improved Crisphead is an ideal choice for hydroponic growers looking for iceberg-type lettuce to add to their garden.
Little Gem Lettuce
Type: Romaine / Cos
Time to Maturity: 50 days
Best for: tight growing spaces
Best way to harvest: the whole head
This dwarf variety is a fantastic choice for those short on space. You can fit a lot of the Little Gem’s tiny heads in a compact space, and they are excellent for slicing.
Muir Lettuce
Type: Loose Leaf
Time to Maturity: 50 days
Best for: disease resistance and heat tolerance
Best way to harvest: cut-and-come-again
Muir lettuce is a frilly, crisp, and mild-flavored loose-leaf variety with excellent heat tolerance. This variety will give you more room for error if you worry about controlling the temperature. It also boasts resistance against downy mildew and lettuce mosaic virus.
Winter Density Lettuce
Type: Romaine / Cos
Time to Maturity: 55 – 65 days
Best for: heat and frost tolerance
Best way to harvest: cut-and-come-again
This hardy variety produces compact, buttery leaves. Winter Density is a great choice for anyone who needs romaine-style lettuce that can manage well in various seasons.
What to Grow Next in Your Hydroponic Garden
If you love growing lettuce and are looking for more to grow in your hydroponic garden, check out the Ponics Life blog for more great guides. You can also join the Ponics Life club for notifications whenever a new guide is released, invitations to webinars and courses to help you grow your knowledge, and access to exclusive products.
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