Gardeners can grow many types of lettuce

| Friday, March 29, 2013, 8:57 p.m.

Lettuce has been a favorite garden crop since Colonial times. Today, each American downs about 30 pounds of it per year. It's no wonder, really, that this leafy vegetable is so popular. It's full of antioxidants and vitamin K, contains plenty of vitamins C and A (especially darker-colored types), and is a good source of foliate. It's also unbelievably easy to grow.

Commercial lettuce production focuses largely on a small handful of lettuce varieties that are uniform in growth, have a decent shelf life, and are shippable. But for home gardeners, the choices are far more extensive.

Lettuce is generally categorized into five distinctive groups:

• Romaine, or Cos, lettuce forms an upright, elongated head (think Caesar salad).

• Loose-leaf or leaf types have leaves of various shapes, loosely arranged around the stem.

• Crisphead lettuces form a dense, compact head, surrounded by a few looser leaves (iceberg fits in this category).

• Butterhead (also commonly called Bibb, Boston or Buttercrunch) varieties form very loose heads of tender, sweetly flavored leaves.

• Stem lettuce has elongated leaves with a very bitter flavor and is commonly used in Chinese cuisine.

But no matter what type (or types) of lettuce you decide to grow, a few simple steps will ensure your success. First and foremost, lettuce is a cool-season crop, growing best when the daytime temperatures are between 60 and 70 degrees. For those of us in Pennsylvania, that means planting lettuce from early to late spring and then again at the beginning of fall. Lettuce dislikes heat and will bolt (or go to flower) when temperatures rise and the days lengthen.

Position lettuce where it receives a minimum of six hours of direct sun (though summer-grown crops tolerate, and may even prefer, full shade) and amend the soil with plenty of organic matter. Lettuce grows best with a soil pH of 6.0 to 6.5. Test your soil every few years and adjust it accordingly.

The easiest way to grow lettuce is by seeding it directly into the garden. Seeds can be sown according to package instructions when soil temperatures range from 40 to 70 degrees. My first lettuce crop of the season usually gets seeded into the garden in late March or early April and I continue to sow more seeds every two or three weeks until the heat of summer arrives.

Many gardeners who sow seeds of lettuce directly into the garden, plan to harvest them in the “baby” stage. These young, undeveloped greens are meant to serve as a “cut-and-come-again” salad and they are sown very thickly. If, instead, you want to grow full heads of lettuce, plan to sow the seeds 1 to 3 inches apart and then thin the resulting seedlings so they are spaced 6 inches apart.

Keep your lettuce plants well-watered, providing them with a minimum of an inch of water per week. They have a very high water content and moisture stress promotes early bolting and bitterness. Mulching lettuce plants with compost, leaf mold, straw or hay keeps moisture levels stabilized and cuts down on necessary watering. If you can, irrigate in the morning to discourage fungal issues and pest woes. Fertilize with a water-soluble liquid fertilizer like fish emulsion or liquid kelp every two to three weeks until harvest.

In next week's column, I'll share some of my favorite lettuce varieties with you.

Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio. She is the author of several gardening books, including “Grow Organic” and “Good Bug, Bad Bug.” Her website is

Send your gardening or landscaping questions to or The Good Earth, 503 Martindale St., 3rd Floor, D.L. Clark Building, Pittsburgh, PA 15212.

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