6 Tips for Growing Heads of Lettuce Through Summer Heat

Some aspects of growing summer lettuce can be challenging while others are pretty simple. Follow these tips for success in the garden.

by Jesse Frost
PHOTO: Shutterstock

Whether you are a market farmer or just a backyard gardener, head lettuce is a delicious and important crop for you all summer. Though we tend to think of lettuce during the shoulder seasons, there is a lot to be said about a fresh salad with sliced tomatoes and peppers or simply a fresh BLT throughout the summer. The good news? Growing good summer head lettuce is possible—if you do it the right way.

There are some elements of growing summer lettuce that can be challenging and some that can be surprisingly straight-forward, but heed each of the below tips and you can have head lettuce on your market or dinner table all summer long.

1. Select the Right Lettuce Varieties

Perhaps obviously, your favorite winter lettuce might not make the best summer lettuce. What works the best in the summer is a variety that has been bred to withstand high temperatures and very long days. Several varieties bill themselves this way in seed catalogs, so it is fairly easy to track them down by searching through your favorite seed purveyor’s catalog to find the exact crop you are looking for. Southern Exposure has some as well as Johnnys, high Mowing and Fedco. Our personal favorite is Muir, but the key here is to try several and not just bank on one or two. Your conditions will be different so hedge your bets!

2. Germinate Lettuce in a Cool Place

Lettuce does not really germinate in temperature above 75 degrees F, so it is critical for summer lettuce that you do not try to germinate it directly in the soil, or in the greenhouse. The ideal place is under cover or in your basement. In the heat of the summer we will put lettuce trays in our cooler overnight then germinate them in a shady area over the next two days. Make sure to get them into light immediately when you see sprouts and keep the moist.

3. Harden Off the Plants

When the plants are almost ready to transplant, leave them in direct the sun for a few days to harden them off. Make sure to keep them misted and cool during this period, but this will reduce transplant shock when they go in the garden.

4. Transplant in Wet Conditions

Make sure when planting that the ground and the soil block or cell with the lettuce in it are wet when transplanting. This will reduce transplant shock and ensure more success.

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5. Provide Shade

If you have some way to shade (even planting under a small tree) that can be a great way to get your plant established in those first two weeks. The first two weeks are critical for success. Once established, you can remove any shade cloth. Around 30% shade is fine for most areas.

6. Mist Often

We like to lightly mist our plants in the middle of the day to cool them off. Lettuce won’t just become bitter if it gets too hot, but it will also either bolt or get scorched. So that light misting will prevent that and also keep the plants at a temperature they like to grow (below 80 degrees F).

Follow those few rules and you can have heads of lettuce all summer long.

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