Growing Lettuce on the High
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
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
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
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.
TIME TO GROW
|Merveille des Quatres Saisons
||unusual bibb type, reddish
leaves with cranberry -red tips, pale light green heart; holds flavor in hot weather but
||60 to 70 days
||Shepherd's Garden Seed Co.
|Black seeded Simpson
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
|romaine; 10-12" deep red head, good flavor, crisp, slow to bolt;18th
||60 to70 days
||See Garden City Seeds above.
||head type; small crumpled green on globed heads; fine for hot
||55 to 67 days
||Ornamental Edibles 3622 Weedin Ct. San Jose, CA 95132
TIME TO GROW
||romaine; sweet delicious flavor; med-slow bolt; neatly folded
, slightly savoyed leaves with creamy center
||59 to 79 days
||Johnnys Selected Seeds
310 Foss Hill Rd. Albion, ME 04910 Free catalog (207)437-9294
||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,
||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
||head; disease and TB resistant large firm heads; developed
for hot dry areas for summer cultivation
||Nichols Garden Nursery
1190N. Pacific Hwy. Albany. OR
TIME TO GROW
||butterhead French heirloom; very cold hardy
||Abundant Life Seed Foundation
P.O. Box 772 Port
Townsend, WA 98368
||romaine; dk green 9-10" compact heads; tighly folded
rounded tops; sweet flavor
||54 to 64 days
||See Johnnys Selected Seeds andOrnamental Edibles above.
||head; hardy though does not stand heavy frost; firm light
green crinkled heads
||The Cooks Garden P.O. Box 535 Londenberry, VT 05148
||crisphead; magenta to light green leaves with excellent
flavor; vigorous; very cold hardy
||Pinetree Garden Seeds
box 300 New
Glouchester, ME 04260 (207) 926-3400
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