If your yard is small or you don’t have much available space for growing (more) lettuce, you might be thinking about whether you can plant lettuce in a partially shaded area.
Lettuce not only thrives in partial shade, but during the hottest part of the year it is actually preferred to grow lettuce in a partially shaded area.
Light Requirements of Lettuce
Lettuce, like all leafy green vegetables, grows best in full sun. The more hours of sunlight your lettuce plants receive, the faster they will grow.
If growing lettuce under grow lights, use a light cycle (photoperiod) of at least 10 to 12 hours, up to 18 hours for optimal growth.
But also like most leafy vegetables, lettuce can tolerate partial shade or even temporary full shade. In some instances, it may be even more beneficial to grow lettuce in partial shade.
Can Lettuce Get Too Much Sun?
While lettuce grows fastest in full sun, lettuce does not tolerate high heat. Unfortunately, in the height of summer, full sun all day long also means exposing your lettuce to high heat.
What Heat Stress Does to Lettuce
Lettuce grown in hot and dry conditions will bolt (produce a flower stalk) relatively quickly. This is great for saving seeds but not for eating. Bolted lettuce is undesirable for us as gardeners because when it bolts, the leaves get smaller and more bitter.
An example of how quickly lettuce can bolt: I had spring-planted lettuce that lasted well over a month without bolting. In late June, I replanted some lettuce and in less than two weeks I noticed it was starting to bolt.
Reasons Why You Should Grow Lettuce in Partial Shade
Growing lettuce in partial shade protects your lettuce from the searing heat of the sun, especially in the summer months.
Even though lettuce grown in full sun will grow faster, you can actually get more harvests overall from partially shaded lettuce than those grown in full sun because you can harvest continually for a longer period of time.
My rule of thumb is to grow lettuce with as much sun as possible in the early spring and late fall months, when days are much cooler, and grow in partial shade in the summer. But this will vary based on your own climate.
Disadvantages of Growing Lettuce in Partial Shade
The main drawback of growing lettuce in partial shade is that your lettuce plants will grow more slowly and leaves may appear slightly more leggy.
For most people, this is a small price to pay for being able to harvest lettuce over longer periods of time.
How to Provide Partial Shade for Growing Lettuce
There are a few approaches to take when choosing a partially shaded area to grow lettuce. You can choose either an area that gets dappled light (patches of light passing through a taller plant) or an area that is fully or partially shaded for a part of the day.
An example of dappled light would be under a tree canopy or a trellis over a patio.
The other approach can involve planting your lettuce next to a fence or wall that will block the sun for half of the day. You could also plant on the west or east side of a row of taller vegetables. An example would be planting lettuce next to tomato plants, which will shade the lettuce for part of the day as they grow taller. Lettuce has a relatively shallow root system so it won’t compete with tomatoes as long as they’re planted more than a foot away from the tomato stem.
One benefit of growing lettuce in containers is that you can move your lettuce plants to areas with more or less shade depending on the conditions. For example, if you’re growing spring lettuce and a few days of a heat wave is forecast, you can move your container lettuce into a shady area until it passes.
What if you already have lettuce planted in the ground and in full sun? In this situation, you can use shade cloth, which is a woven netting, usually in black or green, which is designed to shade out a certain percentage of sunlight. For lettuce growing in the middle of summer, you can cover them with 30-50% shade cloth which will significantly reduce the amount of heat stress in your lettuce.
Can Lettuce Grow in Full Shade?
While lettuce can grow in full shade, you will have poor results. Fully-shaded lettuce will grow much more slowly while also producing fewer leaves and the ones they do produce will be smaller and narrower.