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THESE Are the Nutrients Your Hydroponic Lettuce Needs

THESE Are the Nutrients Your Hydroponic Lettuce Needs

Growing hydroponic lettuce is a rewarding practice, but unlike growing it in soil, you need a clear understanding of exactly what nutrients it needs.

What are the best nutrients for hydroponic lettuce? Calcium, potassium, and magnesium are the main nutrients that hydroponic lettuce needs to grow and develop in a healthy manner. Nitrogen and phosphorus are also crucial nutrients for hydroponic lettuce. Calcium is perhaps the most important nutrient as a lack of it causes burned or wilted leaves.

Few things are more rewarding than growing your own food, and when you can do that hydroponically, all the better.

However, your best efforts will be for naught if your lettuce isn’t receiving the nutrients required for optimal growth.

As you read through the following, you’ll discover what nutrients are required the function they serve, signs of deficiency, and recommended amounts.

Soon you’ll be well on your way to enjoying healthy, thriving, productive lettuce plants! 

5 Essential Nutrients for Healthy Hydroponic Lettuce Growth

A gardener lifting a head of green oakleaf lettuce from an aquaponic system.

Hydroponic lettuce requires five essential nutrients to be as happy and healthy as possible: nitrogen, phosphorus, potassium, calcium, and magnesium.

Below, we discuss each one in detail, including how much is recommended and common signs of a nutrient deficiency:


Nitrogen is one of the most important nutrients to think about when growing hydroponic lettuce.

It not only directly affects how tall (and quickly) plants’ leaves grow, but it also impacts the level of food production and processing occurring in the growing plants.

As lettuce are plants that basically consist of nothing but leaves, nitrogen is an absolutely essential nutrient.

Recommended Amount: 

The most recommended nitrogen amount for your hydroponic lettuce nutrient solution is approximately 5 (for example, an NPK of 5-10-15).

Signs of Deficiency:

A lack of nitrogen in hydroponic lettuce plants shows up first as a slight shrinking of roots.

The longer your lettuce is lacking proper nitrogen levels, the leaves begin changing color from healthy, vibrant green to lighter shades of green and eventually yellowing completely.


Phosphorus is a crucial nutrient for most hydroponic plants, including lettuce. It affects the speed of growth and healthy development of the plant.

Phosphorus aids plants in storing and transferring energy from processed food/sunlight. As far as hydroponic lettuce goes, a higher level of phosphorus is required than with other crops.

That said, hydroponic lettuce grows more rapidly from start to finish than other crops as well.

Recommended Amount: 

The most commonly recommended phosphorus ratio for hydroponic lettuce is between 15 and 20 (for example, an NPK of 5-18-20).

Signs of Deficiency:

If your hydroponic lettuce is lacking phosphorus, the first signs are typically the plants’ leaves turning from bright green to dark green in color.

Prolonged phosphorus deficiency sees lettuce leaves with purple or red margins. The leaves also take on odd shapes and may develop gnarly stems also.


Potassium is another main nutrient needed by most plants, including hydroponic lettuce. It is responsible for plants producing large and healthy leaves.

As lettuce is literally all leaves, out of all of the essential nutrients your hydroponic lettuce needs, potassium is required in the largest amounts by far. 

Recommended Amount: 

The recommended amount of potassium needed to grow hydroponic lettuce ranges from 20 to 40 (for example, an NPK of 8-10-38).

Signs of Deficiency:

When hydroponic lettuce is lacking efficient levels of potassium, this particular deficiency shows up in the form of wilting and spotted leaves that also darken in color (from bright green to dark green).

The margins and tips of the lettuce may also turn slightly gnarly and develop chlorotic spots.

Several young hydroponically grown lettuces on grow tray against a black background.


One of the most essential micronutrients for growing healthy hydroponic lettuce is calcium, believe it or not.

In the garden, lettuce absorbs large amounts of calcium from natural sources like decaying snail shells and eggshells as well as from fertilizer and the soil itself.

In hydroponic lettuce, a proper level of calcium promotes crisp leaves with little to no tip burn.

Recommended Amount: 

Hydroponic lettuce requires a healthy dosage of calcium, the PPM of your system should read between 100 and 150 (15-0-0 NPK).

Signs of Deficiency:

Hydroponic lettuce with a calcium deficiency is easy to notice: it’s darker than it should be, possibly wavy, and has tip-burn.

New growth lacking calcium shows up as young leaves speckled with brownish-gray spots.


The second micronutrient that’s super critical for healthy hydroponic lettuce is magnesium.

It’s the nutrient that is responsible for activating certain enzyme systems in the plant as well as managing a healthy chlorophyll process.

Recommended Amount: 

Hydroponic lettuce water requires approximately a quarter-teaspoon of pure magnesium.

Signs of Deficiency:

The most noticeable signs of a magnesium deficiency in hydroponic lettuce appear as greenish and yellowish “bleeding” on leaf tips and margins.

As the deficiency continues, the veins continue to worsen and entire leaves curl down.

Micronutrients Needed for Hydroponic Lettuce

Aside from the two micronutrients already listed above (magnesium and calcium), hydroponic lettuce (and aquaponic lettuce too) benefits from a nutrient solution that includes any of the following:

  • Boron
  • Chlorine
  • Copper
  • Iron
  • Manganese
  • Molybdenum
  • Nickel
  • Zinc

Best Nutrient Solution for Hydroponic Lettuce

There is no one brand or product that is perfect for feeding every plant species, including hydroponic lettuce.

That said, after careful research, we’ve uncovered one nutrient solution that we feel is best suited for hydroponic lettuce:


The PowerGrow MASTERBLEND Kit is one of the best products currently available online for hydroponic lettuce growers.

The kit comes with three sealed bags of powder-based water-soluble components; one contains a potent mix of nutrients for lettuce, one is a bag of pure calcium, and the remaining bag is Epsom salts. 

The MASTERBLEND recipe is 12 grams nutrient mix, 12 grams calcium nitrate, and 6 grams of Epsom salt per 5 gallons of nutrient solution/water.

Each ingredient requires individual mixing (the ingredients do not mix together – they each go into the water individually).

The solution is 100% water soluble, making it easy for plants to absorb, and it includes everything your lettuce needs to grow and thrive.

The blend is so successful for hydroponic lettuce that it is utilized by both amateur and professional hydroponic growers from all over the world. 

NPK(S): 4-18-38 (MASTERBLEND) and 15.5-0-0 (Calcium Nitrate)

Package Contents: Three separately sealed components: 1 pound of MasterBlend nutrients, 1 pound of calcium nitrate, and 0.5 pound of Epsom salt.

Multiple rows of hydroponically grown lettuce floating in their grow tray.

Related Questions:

Does Lettuce Need a Lot of Nitrogen?

Most leafy greens, such as lettuce, kale, and spinach, benefit from extra-high levels of nitrogen.

It not only affects the speed of growth in leaves but affects the overall size they are capable of reaching as well.

Proper nitrogen levels may be achieved through manure, rich organic compost, or through a product like PowerGrow MASTERBLEND.

What’s the Best Hydroponic System for Lettuce?

When it comes to growing hydroponic lettuce, the Kratky system is hands-down the best due to its low build cost and easy-to-maintain design (not to mention it takes no electrical components!).

Ebb-and-flow and NFT systems, as well as aeroponic systems, are all close runner-ups to the Kratky system.

A Final Word About Hydroponic Lettuce Nutrients

The most important nutrients for hydroponic lettuce are calcium, magnesium, potassium, phosphorus, and nitrogen.

As long as your plants have a steady supply of these essential nutrients, proper lighting, and a stable pH, they should be as big and tasty as can be.

Using a product like PowerGrow MASTERBLEND is one of the surest ways to provide hydroponic lettuce with the nutrients it needs to grow and thrive.