How to grow Lettuce in the Tower Garden

How to Grow Lettuce in a Tower Garden year-round! Simple hacks to blow your mind!

While lettuce may not be one of the most exciting crops to grow in a Tower Garden, it certainly is one of the easiest, if not the easiest crop to grow. It loves the cool weather, while also growing in the heat of the summer, making it a great crop to grow year-round throughout most of the US. Stick with us as we go over how to grow lettuce in a Tower Garden. These simple hacks will blow your mind!

Lettuce is one of the most commonly consumed leafy vegetables in the world, and for good reason. Lettuce, a ubiquitous leafy green in salads and sandwiches, packs a punch not only in flavor but also in health benefits and nutritional value. Rich in vitamins and minerals, particularly vitamins A and K, lettuce contributes significantly to overall well-being. Vitamin A promotes healthy vision, skin, and immune function, while vitamin K supports bone health and blood clotting. Additionally, lettuce contains antioxidants such as beta-carotene and flavonoids, which help combat oxidative stress and reduce the risk of chronic diseases like heart disease and cancer. Furthermore, lettuce is an excellent source of dietary fiber, aiding in digestion, promoting gut health, and contributing to feelings of fullness and satiety.

There are four things to consider when growing lettuce

  • Variety
  • Water
  • Minerals
  • Tips for growing in the summer or winter

Types of Lettuce

There are five main types of lettuce, and you can grow all of them in the Tower Garden

  • Crisphead – These have a tight, round shape and are crisp and crunchy. An Iceberg lettuce falls into this category. While it may not be as nutrient-dense as other varieties, iceberg lettuce is still a good source of vitamins A and K, as well as water content, making it a refreshing addition to salads and sandwiches.
  • Butter Lettuce – They are round, like Crisphead, but the leaves are not as tightly packed. High in vitamins A and K, as well as folate and potassium, butterhead lettuce adds a touch of luxury to salads and sandwiches. Its soft leaves are ideal for creating lettuce cups or wraps filled with savory fillings. Our Bibb, Adriana, and Red and Green Salanova lettuce seedlings fall into this category.
  • Loose Leaf – The leaves on this variety are loosely held together which allows you to cut off individual leaves vs harvesting the whole head, as you would a crisphead or butter lettuce. These varieties are known for their tender, frilly leaves and mild, slightly peppery flavor. Rich in vitamins A, C, and K, as well as antioxidants, leaf lettuce adds a pop of color and flavor to salads and sandwiches. Its delicate texture also makes it a popular choice for garnishes and plate decorations. Our Cherokee, Magenta, Muir, Starfighter, and Spring Mix lettuce seedlings fall into this category.
  • Romaine – Also known as Cos lettuce, is known for its long leaves with a slightly bitter taste. Rich in vitamins A, C, and K, as well as folate and potassium, romaine lettuce offers a nutritional boost to any dish. Its hearty leaves make it an excellent choice for wraps and salads that require a sturdy base. Coastal Star, Bluerock and Breen are varieties of red and green romaine lettuce seedlings that we offer.
  • Specialty Lettuce – Finally, there are specialty varieties like arugula, mizuna, and radicchio, each offering a distinct flavor profile and nutritional benefits. We’re not going to get into growing these in this article though.

When Can You Start Growing Lettuce?

Unlike growing in a traditional garden, you can start growing lettuce on almost any day of the year almost anywhere in the US in a Tower Garden. Lettuce is a pretty fast-growing crop and you’ll go from a seedling to a full head of lettuce in about 4 weeks, under ideal conditions. If you live in an area with harsh summers (>100°) or harsh winters (<30°)try to plant your lettuce at least 4 weeks before those temperatures are expected to hit. If you’re growing inside with Grow Lights you can plant your lettuce whenever you want!

Selecting a Variety of Lettuce to Grow

When selecting a variety, it’s important to consider the climate. Lettuce is a cooler weather crop that thrives in temperatures below 80, but some varieties grow well in the heat of the summer in temperatures up to around 95! You’ll find our heat-tolerant lettuce seedling varieties here.

Personal preference plays a part too! Different lettuces have slightly different tastes, textures, and colors, so pick the varieties you like. If you’re not too sure, try one of each to start!

Starting Lettuce Seeds

Starting lettuce seeds is no different from starting any other.

  1. Soak the Rockwool in pH-balanced mineral solution water for approximately 20 minutes. You can either remove a few cups from your Tower Garden reservoir or fill a gallon jug with filtered water and add 10ml (2 teaspoons) of both Mineral Blends A and B. This helps to neutralize the pH of the Rockwool.
  2. Add the appropriate amount of seeds to each Rockwool cube. (See chart below)
How to Gow Lettuce in the Tower Garden How many seeds
  1. Place the tray in full sun, or under lights if you are growing inside. Light is CRITICAL for seedlings, especially in the early days. If they are not getting enough direct sunlight, light from grow lights, or the grow lights are too far away, your lettuce seedlings will start to stretch as shown in the image below. Sadly there is nothing you can do to reverse this if it happens.
Weak Tower Garden Seedlings
Weak lettuce seedlings stretching for light
  1. When your lettuce seedlings are around an inch in size you can transplant them to the Tower Garden. It will usually take between 7 and 14 days for them to reach this size.
Tower Garden Lettuce Seedling
Strong healthy Bibb Lettuce Seedling

Adding Water and Minerals to the Tower Garden


So a quick 101 on water.

You don’t want to use softened water, hard water or, reclaimed water in your Tower Garden, no matter what crops you are growing. Well water is fine, providing it isn’t softened. City water is where it can sometimes get tricky. You may see or hear of some growers that use city water straight from the tap and they’re not experiencing any problems. Our experience (since 2009) is very different. We’ve had customers drive to our farm, purchase strong healthy seedlings and then drive home. Within minutes of transplanting them to their Tower Garden, they begin to wilt. Every time this happened the customer told us they had used city water but they didn’t use a filter. Hmm, so what could be happening?

Some municipalities add Chlorine, which dissipates after about 24-48 hours in the sun, while others add Chloramine. Chloramine is a mixture of Chlorine and Ammonia and unlike Chlorine, Chloramine does not easily dissipate. Chlorine and Chloramine can cause additional stress to all crops, especially in the hot summer months.

For that reason, we recommend filtering city water with an inexpensive filter like this.


One of the biggest mistakes I see new and experienced Tower Gardeners make is adding too much mineral blend. Seedlings don’t require a whole lot of minerals, so if you are starting a Tower full of seedlings you can just use half-strength, which is 10ml of each A and B.

Use the chart below when adding minerals to the Tower Garden. Pay special attention to the temperature! On hot days plants need more water but they don’t need more minerals. That coupled with some evaporation means the mineral solution will get concentrated over time and it’s why we say to add half-strength, and sometimes even quarter-strength, when topping up your Tower Garden. You are much better off slightly under-feeding than over-feeding.

Adding Minerals to the Tower Garden - How many ml

It’s also important to empty your reservoir every 60-90 days. Over time, minerals can build up in the reservoir and excessive and unbalanced minerals in the reservoir can cause tip-burn in lettuce on both indoor and outdoor Towers.

How to Grow Lettuce Tip burn

How to Grow Lettuce in the Summer Months

We’ve met many Tower Gardeners over the years who have struggled to grow lettuce in the summer months. We have grown a few different lettuce varieties through the summer months in both Central and South Florida. Providing you take the right steps you’ll be able to grow all summer long.

  1. Grow a heat-tolerant variety
  2. Use an additional seed or two for leafy varieties to get more lettuce in less time.
  3. Filter city water
  4. Use the correct amount of minerals depending on the temperature.
  5. Harvest lettuce sooner, before it has time to bolt.

We have some other general Summer Time Growing Tips here too.

How to Grow Lettuce in the Winter Months

As I’ve mentioned, lettuce is a crop that thrives in cool weather. It’s a delicate crop so you’ll need to protect it from a frost and temperatures that are below freezing. Thankfully, there are many easy ways to do this.

  1. Use a submersible heater in the reservoir. Set to 68°.
  2. Use a frost cloth on nights when a frost is forecast.
  3. Use a pop-up greenhouse. Check the dimensions fit the number of Towers you are growing.
  4. Grow inside with grow lights.

We have more Winter Growing Tips here too.

How to Harvest Lettuce

There are many ways to harvest lettuce.

  1. Pick or cut individual leaves.
  2. Cut the whole lettuce (Romaine and leafy lettuces only)
  3. Remove the whole head.

The video below will show you how. The most important thing to remember when cutting the whole head is to ensure you are cutting at least two inches above the rockwool cube. Cut it too low and the lettuce will not grow back.

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