How to Grow Butter Lettuce Hydroponically

By: Chris | Last Updated: June 27, 2021

Lettuce, more specifically butter lettuce, is one of my absolute favorite plants to grow. It was my first hydroponic love. It grows fast, and I eat it every day. It is the perfect “first grow” for beginners, and a constant staple in hydroponic gardens, regardless of skill level.

It is easy to grow, hard to kill, and will produce in just about any situation. Even though it is a hardy plant, there are some tips I’ve developed that help increase the yield of hydroponic butter lettuce.

The Best Way to Grow Lettuce

The best way to grow lettuce is obviously hydroponically. All joking aside, hydroponic systems are perfect for water-loving lettuce.

Common question:
“What kind of hydroponic system do I need to grow lettuce?”

My honest answer:
“If you have a hydroponic system, lettuce will grow in it.”

Vertical and NFT systems are popular choices, but I still grow lettuce in a 2-foot by 4-foot ebb and flow system. That 2 by 4 system grows around 24 to 28 heads of lettuce with no problem.

Quick Tips to Grow Butter Lettuce

If you just need the highlights, these quick tips will get you started. Save this Growing Hydroponic Butter Lettuce Tip Sheet for future reference.

Most Suitable Hydroponic Method: Any
Best Grow Medium: Any seed plug/cube
Time to Germinate: 1 to 3 days
Time to Maturity: 27 to 35 days
Optimal pH Range: 5.5 to 6.5
Light Cycle: 12 to 16hrs
EC Range: 0.8 to 1.2 mS
Germination EC Range: 0.6 to 0.7 mS
Growing Difficulty: Very easy

Need more detailed information? Keep reading!

How to Grow Lettuce from Seed

Growing lettuce from seed is easy, and here are five simple steps that prove it. It takes longer to read these five steps than it does to get your first batch of lettuce ready to germinate!

Materials for Germinating Lettuce


Step 1: Mix Nutrient Solution

Start by adding 1 gallon of distilled or reverse osmosis water into a container. I use at least a gallon of water because it makes it easier to measure out and mix nutrients.

Measure and mix nutrients into the water until the solution has an EC of 0.6 to 0.7 mS. Since this is such a weak mixture, it’s important to start with water that has almost zero total dissolved solids (distilled or RO). Tap or well water can have an EC of close to 0.5 mS before you’ve even added nutrients.

Once you’ve hit the nutrient strength target, check the pH of the solution and adjust it to 6.0 using either pH UP or pH DOWN. If you’re using distilled water, you’ll likely need to use pH UP.

Note: If you’re using a 3-part nutrient system, make sure you use all three parts.

Step 2: Fill the Seed Tray

Okay, fill is not really the best word. Add enough nutrient solution to the tray that the bottom 1/8th inch of the seed starter plug will contact the solution. The amount of water needed will depend on the size of your tray and the depth of your insert.

In 1020 trays with a Grodan insert, I normally add close to 3 quarts of solution.

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Recently, I tried out a net cup insert made by Bootstrap Farmer and was really impressed with it. It fits perfectly in a 1020 tray, and the net cups sit low in the tray which means you won’t need to add as much nutrient solution to the tray. This is super handy since it’s a lot easier to move a full tray without spilling nutrient solution everywhere.

Step 3: Soak the Seed Starter Plugs

The soaking method will depend on the type of starter plugs or cubes you use. I use Rapid Rooter plugs, so that’s what I’ll be describing.

Using the solution left in the mixing container, soak the Rapid Rooter plugs. It doesn’t take long; dunk them under the solution for around 30 seconds to make sure they’re fully soaked.

Step 4: Sow the Seeds

Place one seed into each starter plug, and then place each plug into the insert in the tray.

I know what you’re thinking; everyone recommends sowing multiple seeds and then thinning. Honestly, if you have good seeds, that’s a waste. The germination rates in hydroponic gardening are super high. I very rarely ever have a lettuce seed that fails to germinate.

Pro Tip: Use high-quality seeds!

Step 5: On With the Humidity Dome & Lights

Once you’ve planted all your seeds and placed your plugs into the insert, it’s time to cover the tray with a humidity dome. Make sure the vents on top of the dome are closed. Also, place the tray under a fluorescent or LED grow light.

Yep, you read that right! Go ahead and stick that tray under a light right from the beginning. Your lettuce seeds will reward you by sprouting within 24 hours.

Once each seedling has shown its seed leaves – normally around the second day – open the valves on top of the humidity dome. The dome can be removed the next day to prevent damping off.

Alternative Lettuce Germination Method

If you’re low on gardening supplies, this paper towel germination method works great! Be careful transplanting the seedlings into grow cubes. This used to be my go-to method, but it seems to shock the seedling a bit when transplanting. Nothing too serious, but it does slow down growth by a few days.

Grow Butter Lettuce Hydroponically

Be forewarned; what I’m about to share with you is the way I grow butter lettuce hydroponically. These methods may not always mesh with what you read elsewhere. They work.

Grow Butter Lettuce Hydroponically

It doesn’t matter what hydroponic system you use. Manage the nutrient strength, pH level, light intensity & intervals. Give the plants room to grow, and air to breathe. Lastly, try to keep algae, mold, and mildew at a minimum. These are the basic components of growing big, fat, happy lettuce. Now let’s get down to the details!

Hydroponic Butter Lettuce Spacing & Transplanting

Transplanting Size: 1.5 to 2 inches | Plant Spacing: 6 to 10 inches

The general recommendation for spacing butter lettuce is 8 to 10 inches between plants. Personally, I operate in the 6 to 8-inch range and have been happy with the results.

Spacing is important, not just for the size of the plant but also for proper transpiration.

What is Transpiration?
You can think of transpiration as a hot, steamy breath. If you place a plastic bag over a plant, that bag will start to look like the windows of a car parked at “Makeout Point.” Some of the water absorbed by the plant’s roots is released in the form of vapor from the plant’s leaves.Airflow helps improve transpiration and replaces that steamy damp air around the plant with dry air. If you place lettuce close together, make sure you have good fans for airflow; otherwise, it’s gonna be a sticky, sweaty mess in there!Want to learn more?
Evapotranspiration & the Water Cycle (External Link – USGS.gov)

I normally wait until lettuce seedlings are 1 ½ to 2 inches tall before transplanting into my system. This gives them time to develop their first set of true leaves and build a decent root system. The most important thing is to make sure the roots will reach the nutrient solution in the hydroponic system.

How to Transplant Butter Lettuce

Personally, I transplant new lettuce into a hydroponic system with a full-strength nutrient solution. Some people prefer to slowly increase the strength of their solution, but I’ve never found a need for it with butter lettuce. If anything, it only slows down growth until the plant starts receiving the proper level of nutrients.

Hydroponic Lettuce Nutrients

Nutrient Strength: EC 0.8 to 1.2 mS (800 to 1,200 μS) | pH: 5.5 to 6.5

Pro Tip: You don’t have to go crazy with supplemental nutrients when growing lettuce. Basic nutrients aimed at promoting vegetative growth are all your lettuce needs to thrive.

Adding nutrient salts to water will adjust the pH of the mixture. Wait until you’ve mixed the solution to adjust the pH.

When mixing nutrients for butter lettuce, aim for a solution with an EC of 0.8 to 1.2 mS. If you’re using a multi-part nutrient formula, stir each part into the water thoroughly before adding the next part.

If the solution is too strong, add water. If the solution is too weak, mix in more nutrients.

My formula for growing hydroponic butter lettuce is a pH of 6.0 and a nutrient strength of 1.2 mS. I use General Hydroponics Flora Series nutrients, but any good nutrient system will work.

General Hydroponics FloraNova Grow - 1 Qt

One part hydroponic nutrient system

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If you want an easy-to-use option, FloraNova Grow might be perfect. It’s a single-part liquid fertilizer: no multiple-step measuring and mixing. Simply measure out a dose and mix it into your water.

Light Settings for Lettuce Production

Lighting Type: Fluorescent or LED | Light Height: 15 inches | Duration: 14 to 16 hrs ON / 8 to 10 hrs OFF

For hydroponic lettuce, I use 2 100W LED grow lights. The grow lights hang 15 inches above the growing surface. I’ve tested this height for over a year with great results, and have not had any issues with leaf burn, wilting, or spotting. I leave the lights at this height through the entire growing cycle.

Pro Tip: Watch the lettuce. It will tell you if the light is right. If the lettuce looks like it’s stretching out toward the light (legginess), move the light closer to the plant. Alternatively, if the lettuce looks like the light is burning it, move the light further away. 

Grow Light Height for Hydroponic Lettuce 15

I have both lights plugged into an electric timer. The timer runs the lights for 14 hours per day and is off for 10 hours per day. I use this lighting duration for everything except germination.

During the germination process, the lights run a 12 on/12 off schedule until the seedlings are transplanted into the hydroponic system.

Why two small lights instead of one big light? I don’t always plant the entire grow bed at one time. Having two lights allows me to split the bed in half and only provide light to the side that needs it.

Fluorescent or LED lighting makes the most sense for small to medium indoor gardens. Both have relatively low heat outputs and are inexpensive to run on a daily basis.

Most 100W LED grow lights will easily handle up to 2’x2′ gardens. If you’re planning a 2’x4′ garden, you can use two 100W grow lights or a single 200W light.

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09/21/2021 01:53 pm GMT

The market for LED lighting is extremely competitive. Prices continue to fall while quality rises. One of my favorite “budget” brands is VIPARSPECTRA. Their lights are evaluated by third-party labs, and they openly share that lab data.

If you’re just getting started, I recommend going with the VIPARSPECTRA P1000. It’s a 100W full spectrum grow light with a dimmable driver and high-quality diodes.

If you choose to go the fluorescent route, pick a light with the same footprint as your garden. If you’re planning to grow leafy greens, like lettuce, use 6500k bulbs. If you want more info about grow lights, check out: Beginner’s Guide to Grow Lights.

Airflow & Temperature

Temperature: 60 to 75°F (70 to 75°F Germination)

Make sure you provide good airflow across the lettuce to reduce the risk of mold, mildew, tip burn, and other plant problems. Airflow also helps promote transpiration. In the 2’x4′ bed, I use two small 6-inch clip fans.

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09/21/2021 10:13 pm GMT

Butterhead lettuce is more adapted to warm temperatures than many other lettuce varieties. Optimal temperatures range from 60 to 75°F. For germination, a slightly warmer temperature range of 70 to 75°F will produce seedlings quicker.

These temperature ranges make butterhead lettuce an ideal indoor plant.

My Favorite Hydroponic Lettuce Varieties

I love growing a variety of butter lettuce. After all, it’d be boring if all your lettuce looked exactly the same. The varieties below will give you an awesome color combination in the garden and on your plate.

In addition to their distinct visual differences, each of these varieties will deliver subtle differences in flavor and mouthfeel. I hope you love them as much as I do!

If you’re looking for the quintessential butterhead lettuce, start with the Buttercrunch from True Leaf Market.

True Leaf Market

High Mowing Seed Co.

Harvesting Butter Lettuce

The “smartest” way to harvest butter lettuce is by using the pick and come again method. Simply remove the larger outer leaves of the plant, leaving the rest of the plant to continue growing. This method stimulates rapid growth, and a single butter lettuce plant will continue to produce for a couple of months using this method.

If you’re growing multiple plants, remove three or four leaves from each plant for an almost endless supply of lettuce.

You can start harvesting those luscious leaves once they reach around 3 to 4 inches in length. Don’t worry about pulling out a tape measure; just eyeball it. When they look big enough to eat, they are.

Why I Love Hydroponic Butter Lettuce

Simply put, it’s hard to kill. Butter lettuce will withstand wide pH shifts, a fairly broad range of nutrient strengths, and will grow with inexpensive grow lights.

Since it doesn’t flower or fruit, you won’t need a bunch of different supplements. Plus, if you’re growing indoors, you’ll barely have to worry about bugs or other pests.

Hydroponic lettuce grows fast! Following the same steps I’ve shared here, butter lettuce can be harvested 27 days after planting seeds.

Finally, butter lettuce is the ultimate confidence builder for new gardeners. It germinates and matures quickly, and it will tolerate a lot of mistakes along the way. If you’re on the fence about hydroponic gardening, climb down and start growing lettuce!

Fact Sheet - How to Grow Hydroponic Butter Lettuce

FAQ

How Long Does it Take Lettuce to Grow From Seed?

27 to 80 days. How long it takes lettuce to grow from seed depends on the variety being planted. Butterhead varieties can be harvested in as little as 27 days after planting, while head lettuces can take up to 80 days to reach full maturity. Leaf and romaine varieties reach maturity within 45 to 60 days of planting.

Can you Grow Butter Lettuce Indoors?

Yes, you can grow butter lettuce indoors. Butter lettuce or butterhead varieties of lettuce grow exceptionally well year-round indoors thanks to the reduction of pests, diseases, and a climate-controlled environment. Not only will lettuce grow indoors, but it will also normally produce a higher yield when compared to outdoor planting.

What is the Best way to Grow Lettuce?

The best way to grow lettuce is by using whatever method you have available. Lettuce is possibly the easiest vegetable in the world to grow. As long as it has basic nutrients and slightly acidic soil or water, it will grow. If you don’t have a grow light, put it in a sunny window and watch it grow.

How to Plant Hydroponic Lettuce

Wet a seed starter plug with a weak nutrient solution. Place a lettuce seed in the starter plug. Cover the start plug with a humidity dome or plastic bag to keep the humidity level high. Make sure the starter plug stays damp with nutrient solution. When the lettuce develops its first set of true leaves, it’s ready to transplant into a hydroponic system.

How to Store Hydroponic Lettuce

Once harvested, fresh hydroponic lettuce can be stored in a refrigerator at a temperature of 32 to 38°F for 2 to 3 weeks. Leafy greens, like lettuce, prefer high humidity. If your refrigerator has a crisper drawer, place lettuce in the drawer and close the drawer vent completely to raise the humidity level.

When to Transplant Hydroponic Lettuce

Hydroponic lettuce can be transplanted into a hydroponic system as soon as the roots can reach the nutrient solution in the system. In nutrient film technique, ebb and flow, and Kratky systems, lettuce can be grown from seed in the hydroponic system itself. Alternatively, you can wait until lettuce seedlings reach a height of 1 ½ to 2 inches before transplanting.

How to Grow Lettuce Faster

The easiest way to make lettuce grow faster is to increase the lighting duration. There is a noticeable difference in growth when switching from a 12-hour light cycle to a 14 or 16 hour light cycle. Make sure you leave some sleepy time in the dark for your lettuce. It needs its rest too!

How to Grow Lettuce Year-Round

The easiest way to grow lettuce year-round is by growing indoors. A climate-controlled environment with a temperature of 60 to 75°F is ideal for lettuce production. In most cases, additional lighting will be needed for indoor growing.

Lettuce can be grown in a greenhouse during the colder winter months in some areas, but greenhouses can become too hot in the summer months without additional climate control.

How to Grow Lettuce That is not Bitter

To keep lettuce tasting sweeter longer, keep it cool. Lettuce, along with other leafy green vegetables, develop a bitter taste as soon as they start to bolt. Most varieties of lettuce won’t tolerate temperatures over 75°F for long periods of time. Exposure to higher temperatures will cause lettuce to bolt prematurely.

Beyond temperature, lettuce can become bitter when it’s not getting enough water. That’s not a problem if you’re a hydroponic gardener… Unless your reservoir runs dry.

Chris Cook started Happy Hydro Farm to share his passion for hydroponic gardening! Growing your own food is incredibly rewarding both physically and mentally. His mantra - "Take excellent care of your plants, and your plants will take excellent care of you."