hydroponic lettuce nutrients

How to Grow Lettuce

Growing Lettuce in a Hydroponic System

Whether you are a novice grower or an expert gardener, lettuce is one of the easiest plants to grow in a hydroponic system. Lettuces require a relatively high amount of water, which makes them a great plant for any style of hydroponic system. In fact, lettuces are composed of nearly 95 percent water!

How to Grow Lettuce – Seeds or Starts

The first step in growing lettuce hydroponically is acquiring seeds or starts. If you are starting your lettuces from seed, it is best to first plant your seeds in a nursery flat under a humidity dome. By starting your seeds in a separate nursery flat, you will be able to choose the hardiest and healthiest lettuce starts to transfer into your hydroponic system.

Although you can start your lettuce seeds in almost any medium, you should consider selecting a medium that will work best for your particular hydroponic system. Commercial starter plugs can make the transplanting process smoother since they retain their shape better than loose mediums like soil or gravel. Peat moss, rockwool, and composite plugs all work well in hydroponic systems and provide a stable base for the seedling to grow its roots. Once the second set of leaves emerge on your lettuce starts, they are ready to be transplanted into your hydroponic system.

When you place your lettuce starts into the hydroponic system, make sure that you leave enough room for each start to develop into a full size head of lettuce. Otherwise the plants will overshadow each other and prevent the lettuces from getting enough light. Crowded plants can also become stressed, which increases the likelihood for pests or plant diseases.

How to Grow Lettuce – Light, Temperature, and Nutrient Requirements


Most lettuce varieties require approximately 15 to 18 hours of sunlight. However, lettuces can also bolt, or flower, when the temperature gets too high. For this reason, many outdoor growers will shade their lettuces during the hottest part of the day.


The temperature for lettuce should remain between 55 and 75 degrees Fahrenheit. However, some varieties will tolerate temperatures as low as 45 degrees. Check your local almanac to discover the best planting times for lettuce in your area.


Since it is a leafy plant, most lettuce varieties require a nitrogen-rich nutrient solution. There are different thoughts regarding pH on how to grow lettuce. Your best bet is to keep the pH between 5.5-6.5. However, you should always check the nutrient and pH requirements for your particular variety of lettuce.

How to Grow Lettuce – Harvesting

In approximately two months, your lettuce will be ready to harvest! However, you can stagger the planting of your lettuces to ensure that you have a constant supply of full-grown plants. Although lettuces can live longer than 130 days, the plant will start to bolt if left to grow to maturity. Bolting is when the lettuce prepares to flower by sending out a flowering stem. Although this is a great way for you to harvest your own lettuce seeds, it also creates a bitter flavor in the lettuce plant.

How to Grow Lettuce – Pests and Diseases

Lettuce is particularly susceptible to cutworms, nematodes, and aphids. For this reason it is recommended that you use an organic pest and plant disease prevention program in any type of lettuce garden. Ladybugs are excellent beneficial insect to introduce into any garden. Neem oil is an effective organic pesticide that has the added benefit of inhibiting many plant diseases. Happy growing!