Cool Weather: Just Right for Lettuce

It’s History

In temperate U.S. regions, these are the cooler weather months, a time in which leafy greens can thrive. We want to spotlight lettuce, one of the easiest to grow leafy green options. It has a starring role in one of our culinary courses, the salad, and if tended properly, can produce a continuous, bountiful harvest before the appearance of extreme heat.

Lettuce was first cultivated by ancient Egyptians. Plants were grown so that their seeds could be pressed for their oils, and of course, for their tasty leaves. The oils have been used by Egyptian herbalists and folk medicine to relieve pain, and as a sleep aid. Lettuce was also used in spiritual ceremonies. The tale is that lettuce was what lent the reproduction god, Min, endless vigor for procreation, and thus, lettuce leaves were also presented as offerings to images of Min and during ceremonies to honor him. Depictions of lettuce for these tributes were to no surprise, somewhat phallic, a representation of what we today call the romaine type lettuce. Egyptians introduced Greeks to lettuce, who then introduced them to Romans, and as they say, the rest is history.

Lettuce Varieties

Lettuce is a member of the daisy family, Asteraceae. It is rich in vitamins A and K, and also a source of iron and folate. The most common types include romaine (AKA cos lettuce), head (AKA iceberg or crisphead), and looseleaf (AKA cutting lettuce). However, there is also butterhead (AKA Boston or Bibb lettuce), red leaf, summercrisp (AKA Batavian or French crisp), oilseed, and celtuce (AKA stem or Chinese lettuce) types. The latter two types are lettuces cultivated for their oil, and stems, respectively.

Browse Purchase Options

You can find any number of lettuce choices at your local nursery and online stores. We have had great success with Vivian lettuce (a more tender romaine variety) and Burpee’s Looseleaf Blend. Select the buttons below to view some other purchase options.

Temperature Requirements

Most lettuce grows best at temperatures between 60 and 65 degrees. The closer temperatures get to 80 degrees or sudden extreme jumps in temperatures can cause lettuce to bolt. When this occurs, lettuce produces a large center stalk, flower and eventual seeds in response to distress. At this point, the lettuce is often bitter and too tough to be palatable.

There are some varieties that are cultivated for greater heat tolerance, but still there are limitations. Summercrisp types of lettuce have bolt-resistance, but the flavor profiles and smaller size of other lettuce varieties make gardeners return to them instead, year after year.

So, starting lettuce in early spring and/or late summer/early fall is best for temperate climates. I recommend sowing indoors first if temperatures have not yet consistently reached ~50 degrees in the spring, and if temperatures have not dropped to ~70 when preparing for fall crops.

Best for Containers

Lettuce types best suited for planters/pots are looseleaf, romaine, butterhead and red leaf due to their spacing requirements. The other advantage to growing these types is early gratification! Who wants to wait months before they can harvest because they picked a variety that requires them to wait until a head has formed? Not me! Not to mention, these harvest-as-it-grows types are more nutritious. My favorites are salad bowl lettuce, a looseleaf type and Vivian lettuce, a romaine type that has the texture of butterhead.

What Do I Need to Get Started?

Choose your location. Lettuce does like direct sunlight but will last longer if it is at least partially in the shade during the hottest part of the day.

Choosing the Right Container

You will need a food-safe pot that is at least 6-8 inches deep. Some gardeners use long rectangular planters akin to deck rail planters or window boxes. Others use round pots or whatever they have at their disposal. It is just important that the planter you select, permits you to space your lettuce plants at least 4-6 inches apart for adequate space to grow. If using round pots, those with diameters at least 8-12 inches will permit you to house multiple plants. I have used terra cotta pots, as their permeability helps decrease the likelihood of overwatering and root saturation. Click here for our planting guide.

Planting and Care

It is recommended that you practice succession planting with lettuce. By sowing seeds every 2 weeks, you will have continuous harvest opportunities vs. numerous plants reaching maturity and harvest-ready at once. If you have already started you seedlings indoors, harden them off for transplanting. Otherwise, get your seed selection and directly sow into pots. If using seed, you can sprinkle seed generously about 1/4 inch below soil surface or space out and plant several seeds in mini-hills, and thin them out later.

You may cover with garden mesh for insect/pest control and/or plant among potted marigolds, highly fragrant herbs like basil, thyme, rosemary, lavender, geranium to deter insect pests. You may also plant in shadow of larger plants for shade during hotter hours of the day to slow the occurrence of bolting.

Now, just keep the soil moist (not sopping), watering at the soil line vs. on the foliage when possible and monitor for pest issues. If aphids appear, spray leaves with jets of water to clear, knock them off into container of soapy water, or spray with water and mild soap mixture or other natural insecticide spray. Click here for more about safe pest control spray options.

Harvesting

As soon as your lettuce plants have enough exterior leaves, that are large enough to suit your culinary purposes, you may either gently snap or snip these outer leaves (with shears), just above where they connect at the base. Make sure you use clean tools. These leaves will continue to grow back so long as your plant is healthy and in its growing phase. If you wish to harvest the entire plant (usually not desired until nearly full or maturity, you can cut about 1-2 inches above the base, or cut the head (if applicable) at the soil line, just below the outer leaves. In some instances, if the temperatures and conditions permit, new leaves may grow.

Submerge and then rinse harvested leaves in cool water and then cold. Gently shake or “run through” salad spinner to mostly dry. Wrap leaves in or layer between damp paper towels and insert in a food storage bag. Do not close bag entirely. Refrigerate and store in your vegetable crisper/drawer.

Let’s Collaborate!

Are you growing lettuce? Let us know which varieties you selected, share a couple of pictures, and/or maybe even a review of your selections. Enjoy the journey!