Lettuce (Lactuca sativa) is one of the easiest
cool-season vegetables to grow. Although it withstands light frost,
sunlight and high summer temperatures usually cause seed stalk formation
(bolting) and bitter flavor. Slow-bolting or heat-resistant varieties
are available and are recommended for extending the lettuce-growing
Most gardeners who grow lettuce raise the loose-leaf
type, with either green or reddish leaves. This type is a fast-growing,
long-lasting lettuce used for salads and sandwiches. Leaf lettuce
basically needs only to be planted and harvested.
Butterhead or Bibb lettuce is a loose-heading type with
dark green leaves that are somewhat thicker than those of iceberg
lettuce. Butterheads develop a light yellow, buttery appearance and are
very attractive in salads. A miniature variety of butterhead, Tom Thumb,
is very easy to grow and requires a short growing time. Bibb lettuce
will develop bitterness readily if temperatures go above 95 F.
Romaine or cos is less commonly grown by gardeners but
is a very nutritious lettuce that deserves attention. It too is
relatively easy to grow, forming upright heads with rather wavy,
Crisphead, also known as iceberg, has a tightly
compacted head with crisp, light green leaves. Many South Carolina
gardeners find this type difficult to grow due to high temperatures.
Lettuce is a cool-season crop that prefers temperatures
of 55 to 65 F for optimum growth. This crop prefers a loamy soil with a
high organic matter content. Lettuce seedlings should be protected from
the wind because the young plants are rapidly dried out from the wind.
The optimum soil temperature for seed germination is 60
to 80 F. Raw lettuce seed will not germinate at a soil temperature above
95 F. Use primed seed if possible.
Primed seed will ensure optimum seed germination at
varying temperatures. Buy only certified fungicide-treated seed from a
Dec. 20-Feb. 5
Plant leaf lettuce in rows 1 to 2 feet apart with seed
one-quarter inch deep and 6 to 10 inches apart in the row. It is
difficult to space this small seed precisely at the desired spacing;
therefore, it will usually be necessary to plant thicker and thin the
planting. Leaf lettuce should be thinned when the plants are 1 to 2
inches tall. Leaf lettuce can also be planted in 12-inch-wide beds with
the seed broadcast over the bed.
Head lettuce should be planted in rows 3 feet apart with
12 inches between plants in the row. It is best to grow head lettuce
from transplants purchased from a reputable garden center.
The soil should be well-prepared to provide good
seed-to-soil contact and ensure rapid stand establishment of this
small-seeded crop. Soil crusting over the developing seedlings may make
it difficult to obtain a good stand, especially on heavy clay soils.
Covering the seed with potting soil instead of garden soil will
eliminate crusting problems.
Green Leaf – Green
Ice, Simpson Elite
Red Leaf – Red
Sails, Lolla Rosa
Head – Ithaca,
A soil test is always the best method
for determining the fertilization needs of a crop. Follow the results of
a soil test to maintain a soil pH between 5.8 and 6.5 and optimal
fertility levels. Information on soil testing is available in HGIC 1652,
If a soil test has not been taken,
apply 5-10-10 at 3 pounds per 100 square feet before planting. Lettuce
should be sidedressed once during the growing season. Sidedress with
ammonium nitrate (33-0-0) at 1 pound per 100 feet of row or calcium
nitrate (15-0-0) at 2 pounds per 100 feet of row. More frequent
sidedressing may be required if the garden is sandy or if leaching rains
occur. Nitrogen is important for these crops to produce a high-quality,
dark green product.
Water the garden frequently to maintain a uniform
moisture supply during growth. The garden should be watered in the
morning so that the foliage is dry before dark. Water the garden
sufficiently to moisten the soil to a depth of 6 inches. Light
sprinklings will encourage shallow rooting of the plants. The most
critical period for moisture is during stand establishment. It is
important to have a constant uniform moisture supply to produce a
To have a continuous supply of leaf lettuce during the
spring and fall, it is best to grow several plantings during each
season. Head lettuce is generally more difficult to grow than leaf
lettuce. Lettuce does not tolerate hot weather. If this crop is exposed
to temperature or moisture stress, the lettuce will usually have a
Lettuce seedlings are poor competitors with weeds,
therefore weed control is very important with this crop. Cultivation for
weed control should be shallow to prevent root injury.
Tipburn is a physiological disorder that can
occasionally occur on lettuce. It is related to calcium nutrition.
Proper soil pH and watering will help avoid this problem.
By using clear or black plastic mulch, wire hoop and
clear plastic row covers, excellent lettuce can be grown all winter in
South Carolina. On extremely cold nights it may be necessary to cover
the clear plastic with a spunbond-type row cover material.
HARVEST AND STORAGE
Leaf lettuce should be ready to harvest about 75 days
after planting. It can be used as soon as plants are 5 to 6 inches tall.
Bibb lettuce is mature when leaves begin to cup inward to form a loose
head. Cos or Romaine is ready to use when the leaves have elongated and
overlap to form a fairly tight head about 6 to 8 inches tall.
Head lettuce can be harvested as early as 55 days,
depending on the variety. It is mature when leaves overlap to form a
head similar to those available in the stores.
Store in the refrigerator in the coolest area. Crisphead
lettuce can be stored for two weeks under optimal conditions. Leaf and
Bibb will store as long as four weeks if the leaves are dry when bagged.
Insect problems that may be encountered with this crop
include aphids, cabbage looper, corn earworm and leafhoppers. Diseases
include gray mold, Rhizoctonia bottom rot and Sclerotinia drop.
Excerpted from Home Vegetable
Gardening, EC 570, 2002.