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Growing Lettuce on the High Desert

By Sheri Hunter, Master Gardener, Colorado State University Cooperative Extension, Denver County

Lettuce has been grown and used by the Greeks and Persians since 500 B.C.

Today, a huge number of varieties of Lactuca sativa have been bred from early wild forms. Suitable for gardens large and small, ornamental or edible, these varieties are grown from the far north to the south of the North American continent.

The Seed Savers Exchange Garden Seed Inventory (fourth edition) lists 381 varieties of lettuce. Choice abounds. Do you want to grow leaf varieties, romaines or heads with foliage frilly and notched or broad and wavy? Available colors include deep green, white, yellow, bronze, deep red, or burgundy. Some produce perfect compact heads, while others form bright, informal leafy hedges. All add a sort of elegance rare in a vegetable garden.

Lettuces are not only esthetically appealing, nutritionally they are good sources of calcium. Green leafy varieties also supply vitamins A, C, B1 and B2.

Unfortunately, many lettuces are difficult to ship and preserve for marketing purposes. Commercial growers annually supply only a few varieties. In some months of the year lettuce becomes expensive, scarce or altogether unavailable.

There are many reasons to grow lettuce. Considering its popularity in salads, it is a wonder that lettuce isn't more prevalent than ornamental cabbage in Denver gardens.

The answer may lie in the problem of cultivating lettuce in our high desert plain. Lettuces require fertile soil, high in organic matter. Some lettuces prefer cooler, more humid conditions and become tough, scorched or bitter in harsh sunlight and heat.

For the vegetable gardener determined to enjoy the rewards of growing lettuce, here are the keys to success. In Colorado, soil amendment and water conservation are essential. Beyond that, it is simply important to plant the right lettuce, in the right place, at the right time of year.

Soil Amendment and Drip Irrigation

A fertile soil that retains moisture yet drains well, is ideal for growing lettuce. Most Colorado soils will require ample organic matter such as composted, coarse, fibrous material to shoulder apart soil particles. This enables moisture to drain and oxygen to filter into the root zone. Added nitrogen in some form--well-composted manure, or cottonseed meal--is important for the rapid leafy growth that produces the best lettuces.

Even soil moisture and constant surface humidity promote tender lettuce leaves. While overhead watering and surface irrigation enable slugs to travel and fungus to grow, a special technique provides for tender growth while conserving water resources in our arid environment.

Install a soaker hose an inch or more beneath the soil surface in a slightly mounded row before planting seed. This technique keeps the soil surface dry reducing the chances of predation and disease caused by birds, slugs, fungi, and other pests associated with moist conditions.

After seeding, cover the area with a floating row cover tunnel. Leave this tunnel in place throughout the growing season, removing it only to thin or harvest. Thin lettuce progressively. That is, keep the lettuce growth dense rather than widely spaced. Thin plants only as they develop and leaves begin to crowd. Lettuce thickly grown under a row cover holds in humidity for tender leaves even in warm conditions

Lettuce throughout the Year

Lettuce is generally sown directly into the soil, 1/4 to 1/2 inch deep.

Temperature is extremely important when growing lettuce. Generally, lettuces prefer cool temperatures. Lettuce seed sprouts best at 60-65 degrees Fahrenheit. At 80 degrees and above, lettuce seed will sometimes not germinate at all.

Once plants are up and growing, different temperature responses are also seen. Some types bred for northern areas tolerate very cool temperatures--even light frost--but wilt upon sustained exposure to cold. On the opposite end of the temperature spectrum, certain varieties do well in warmth while others bolt or become bitter. Consequently, it is important to select the right lettuce for the right time of year.

Lettuce planted in full sun, especially in south or southwest facing gardens, may experience a sudden rise in leaf temperature, producing a scorched appearance. Moderating this temperature change with floating row cover reduces leaf scorch. Lettuce can be successfully grown in partial shade during hot summer months. Winter lettuces grown in cold frames with southern exposure do produce well. However, gardeners may need to ventilate the frame during the midday hours of warmer days.

With an extra bit of effort at planting time, bountiful lettuce yields are possible on a year-round basis. The esthetic and nutritional, if not the economic reasons for growing lettuce make it a smart and rewarding choice for any Denver garden. The tables below offers a few suggestions of varieties for growing lettuce year round.

Spring/Fall Lettuces





Merveille des Quatres Saisons unusual bibb type, reddish leaves with cranberry -red tips, pale light green heart; holds flavor in hot weather but bolts 60 to 70 days Shepherd's Garden Seed Co.
Black seeded Simpson leaf; light green crumpled leaves; slow to bolt; withstands some heat and drought 40 to 65 days Garden City Seeds 778 US Hwy 93 N. Victor, MT 59840 406-961-4837
romaine; 10-12" deep red head, good flavor, crisp, slow to bolt;18th century variety
60 to70 days See Garden City Seeds above.
Bronze Mignonette head type; small crumpled green on globed heads; fine for hot weather 55 to 67 days Ornamental Edibles 3622 Weedin Ct. San Jose, CA 95132

Summer Lettuces





Romulus romaine; sweet delicious flavor; med-slow bolt; neatly folded , slightly savoyed leaves with creamy center 59 to 79 days Johnny’s Selected Seeds                   310 Foss Hill Rd. Albion, ME 04910 Free catalog (207)437-9294
Sangria butterhead; fancy somewhat wavy leaves tinted with warm rosy read, interior heart blanch pale yellow; slow to bolt and tipburn 55 to 72 days Lockhart Seeds, Inc. P.O. Box 13613 North Wilson Wy Stockton, CA 95205

Free catalog

Red Sails leaf; bronze red leaves form a full rosette, delicately ruffled; mild flavor; holds quality in heat; highly nutritious 40 to 50 days Bountiful Gardens 18001 Shafer Ranch Rd.                   Willits, CA 95490 (707)459-6410

Free main catalog; rare seed catalog

Vista head; disease and TB resistant large firm heads; developed for hot dry areas for summer cultivation 50 days Nichols Garden Nursery           1190N. Pacific Hwy. Albany. OR 97321

Winter Lettuces





Brune d’Hiver butterhead French heirloom; very cold hardy 53 days Abundant Life Seed Foundation          P.O. Box 772     Port Townsend, WA 98368               (360) 385-5660
Winter Density romaine; dk green 9-10" compact heads; tighly folded rounded tops; sweet flavor 54 to 64 days See Johnny’s Selected Seeds andOrnamental Edibles above.
Arctic King head; hardy though does not stand heavy frost; firm light green crinkled heads 80 days The Cook’s Garden P.O. Box 535 Londenberry, VT 05148
Red Grenoble crisphead; magenta to light green leaves with excellent flavor; vigorous; very cold hardy 55 days Pinetree Garden Seeds                   box 300             New Glouchester, ME 04260        (207) 926-3400

Free catalog



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Date last revised: 01/05/2010