Leaf and Mixed Lettuce
·
·
·
·
·
·
·
·
·
·
·
·
·
·
The salad has been around since ancient times, named for the
Latin for salt (sal), in which the greens were seasoned with salt. As an
American food, salads were relatively unimportant until the back to
nature movement of the 1960’s.
·
In 2005, Yuma producers grew over 8,000 acres of leaf lettuce valued at over $120 million. Leaf lettuce is the 3rd ranking crop
grown in the county, based on gross farmgate receipts.
Most of Yuma’s leaf lettuce is shipped by refrigerated truck to markets throughout the US
and Canada.
In the 1970’s, salad became a national obsession as salad bars sprung up everywhere. Along
with increased interest in salad came widening choices of ingredients and more variety in
salad dressings. Tuned-in restaurants served salads and sandwiches bulging with alfalfa
sprouts and avocados, perhaps the two ingredients most identified with salads at that time.
The 1990’s initiated the decade of convenience, with the emergence of the grocery store
"salad mix," pre-cut, pre-washed greens for an easy mixed green salad.
Lettuce is one of the most common cool season vegetables and is a close relative of sunflowers, artichoke, chicory, endive and sunflowers.
Leaf lettuce is a descendant of the weed Lactuca serriola (prickly lettuce), which probably
originated in the region stretching from Asia Minor into modern day Iran. This wild lettuce
now may be found in many places around the world. The wild form is quite bitter, a characteristic that may be attributed to its milky sap. This sap contains lactucarium which is similar to opium in that it has narcotic qualities. There are reports that the Romans ate lettuce to
induce sleep. But don't dive into the salad bar looking for a high. Our modern lettuce doesn't
contain any significant levels of this component.
Thanks to horticultural work from the Roman period on to the present we are now enjoying
around 2,000 years of work in developing our modern improved types and varieties of leaf
lettuce.
Leaf lettuce (often called loose-leaf lettuce) forms loose rosettes of leaves that come in a
range of colors from various shades of green to burgundy including speckled types.
Lettuce is fairly cold hardy and will tolerate light frosts with little or no damage.
In the United States, lettuce is the second most popular fresh vegetable.
Lettuce is believed to be one of the first vegetables brought to the new world by explorer
Christopher Columbus and has been grown in the United States since colonial times.
Per person consumption of all lettuce varieties has been increasing since 1960. In 2004 total
lettuce consumption reached a record high of 34.5 pounds per person.
One of the most common varieties of loose-leaf or bunching lettuce, green leaf lettuce
branches from a single stalk producing a loose bunch and does not form a tight head. This
type of lettuce is also called loose-leaf and Simpson lettuce and varies in color from medium
to dark green. The vivid medium to dark green curly leaves are softer than iceberg, but not as
soft as butter head leaves. A little meatier than iceberg, the flavor of the smooth tender crisp
leaves is delicately mild.
Good-quality green leaf lettuce will have fairly large, loose heads and thick, "crumpled"
leaves. The leaves will be medium to dark-green in color blending to nearly white ribs or
veins. Scratch the stalk and smell. A sweet or bitter smell means sweet or bitter flavor.
Iceberg lettuce doesn't offer much nutritionally, but loose leaf lettuce is nutrient rich. In fact,
loose leaf lettuce provides 5 to 6 times the amount of vitamin A and five to ten times the vitamin A compared to iceberg. Butterhead types are also are good sources of folate, which
helps prevent birth defects and may decrease risk of heart disease.
·
·
·
·

·
·
·
·
·
·
·
·
·
Leaf lettuce is a cool season crop with distinct temperature requirements. The optimal
growing temperatures are 73◦ F during the day and 45◦ F at night. If the temperatures get too
high, the plant may bolt and form a seed stalk. At freezing temperatures, the lettuce is not
necessarily damaged but, the growth slows.
Leaf lettuce grown in Yuma County is produced by planting pelleted seed at 3 inch spacing
on 42 inch rows.
Leaf lettuce grows best in a rich sandy loam soil which provides good drainage and warms
up readily in the cooler days of winter.
Because lettuce is so perishable, it is harvested by hand in the field, packed into boxes or
bins and immediately transported to a cooling facility or fresh cut salad factory.
Leaf lLettuce is also fun to use as a wrap. Add grilled chicken and salsa for a healthy entrée.
Any of several varieties of lettuce with leaves that branch from a single stalk in a loose bunch
rather than forming a tight head. The leaves are crisper and more full-flavored than those of
the Iceberg varieties.
Depending on the variety, leaf lettuce can range in color from medium to dark green; some
have red-tipped leaves. Among the more popular leaf lettuces are oak leaf, frilly red leaf and
crinkly green leaf.
In general, leaf lettuce is more perishable than head lettuce. Choose bunches with crisp,
evenly colored leaves with no sign of wilting or yellowing. As with all greens, leaf lettuce
should be washed and either drained completely or blotted with a paper towel to remove any
excess moisture before being refrigerated in a plastic bag. It will keep this way up to about 3
days.
California and Arizona account for approximately 97% of the U.S. leaf lettuce production.
Production of leaf lettuce in Yuma has increased over 20% from 1998.
Most lettuce seed is coated (i.e., pelletized) with a clay type mixture to provide a small pellet
of uniform size and shape to facilitate precision planter use. Seed treatments (i.e., priming)
are included with some coatings to assist in germination, especially during hot weather conditions.
Because an excess of seed is planted, thinning is required to establish the final stand which
usually ranges between 31,000 to 26,000 plants per acre.
Water cut-off, or the final irrigation, is a critical process in the production of lettuce, as it can
have significant effects on yield and crop quality. Following the last irrigation, all irrigation
related equipment is removed from the field, and the Grower-Shipper, or Shipper, assumes
control of all operations related to harvest.
Most of the leaf lettuce produced in Yuma is harvested into cartons in a "naked" form with
24 heads to a carton.
Kurt Nolte is an area agriculture agent with the Yuma County Cooperative Extension. He can be
reached at 928-726-3904.