SELECTED VEGETABLE CROPS [continued]
Ch. 10, pp. 100 - 103
Crops: intro |
brussels sprouts |
sweet corn |
eggplant | lettuce |
herbs | herb
||Sunny, tolerates shade; prefers shade where
summers are hot.
||Well-drained, loose loam.
||6.0 to 7.0
||Cool (60 to 70° F).
||Moist, but not waterlogged; frequent, light
||Seed leaf or butterhead types as soon as
soil can be worked in the spring, or in late summer. Crisphead
and cos types may be transplanted in early spring or fall.
Start seeds indoors 5 to 7 weeks prior to this date.
||4 to 10 inches by 12 to 24 inches for leaf,
cos, or butterhead. 12 to 15 inches by 18 to 30 inches for
||Hardy perennial, should be mulched in autumn
in areas of Arizona where the soil freezes.
||Medium-heavy feeder, use starter solution on
transplants, sidedress if nutrient deficiencies are noted.
Lettuce, a cool-season vegetable crop, is one of the easiest to
grow. Lettuce withstands light frost; however, sunlight and high
summer temperatures usually cause seedstalk formation (bolting)
and bitter flavor. Slow-bolting or heat-resistant varieties are
available and are recommended for extending the lettuce-growing
season. There are several types of lettuce commonly grown in
Crisphead, also known as iceberg, is the lettuce most
widely available as a fresh market type. It has a tightly
compacted head with crisp, light green leaves. Many gardeners find
this type difficult to grow because it requires a long season and
some of the most advertised varieties are not heat-resistant and
tend to go to seed as soon as temperatures go up. Select a
slow-bolting variety and start seed indoors in late winter or late
summer for best results. Transplant in early spring or fall to
take advantage of cool weather and mulch well to keep soil
temperatures from fluctuating and to hold moisture in. An organic
mulch is more suitable than black plastic after soil warms up.
Mulching also keeps soil off the leaves, reducing chances of
disease from soil-borne organisms.
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, requiring a short
growing time. One head of this lettuce is about right for one or
two services, so this is one lettuce to plant in succession, about
two weeks apart. It may be started indoors for an even longer
season. Bibb lettuce will develop bitterness readily if
temperatures get too high.
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, attractive leaves.
Most gardeners who grow lettuce raise the leaf type,
either with green or reddish leaves. This type is fast-growing,
long-lasting lettuce used for salads, sandwiches, and in wilted
lettuce salads. Leaf lettuce basically needs only to be planted
Sow leaf varieties in rows, 10-20 seeds per foot, in
rows 8-12" apart. Thin individual plants 4-8" apart,
depending on variety. Leaf lettuce also grows very successfully in
a wide bed arrangement; seedlings are thinned to 4-8" on all
sides. Cos and head types should be sown or transplanted 12-18"
apart. If in rows, allow 30" between rows.
Cultivate carefully as lettuce is shallow-rooted. Use
frequent, light waterings to encourage rapid growth, but do not
over water, as this may cause disease of roots or leaves. Overhead
watering should always be done in the morning to give plants time
to dry off. As mentioned above, mulches are helpful in maintaining
soil moisture and keeping leaves off the ground.
Lettuce planted in very early spring should be given
full sun so that the soil will warm enough for rapid growth. For
long-season lettuces, plant so that crops such as sweet corn,
staked tomatoes, pole beans or deciduous trees will shade the
lettuce during the hottest part of the day when temperatures are
over 70º. Inter-planting, i.e., planting between rows or
within the row of later-maturing crops like tomatoes, broccoli,
and Brussels sprouts, is a space-saving practice. Some lettuces,
like Tom Thumb and leaf lettuces, are attractive in flower
Lettuce is best planted in succession, or using
different varieties that mature at different times. Thirty heads
of iceberg lettuce harvested at once can present a major storage
problem! Leaf and Bibb lettuces do well in hotbeds or greenhouses
during the winter and in cold frames in spring and late fall.
||Stem, leaf, and root rots, mosaic virus, big
vein, lettuce drop, downy mildew, bottom rot.
||Aphids, root aphids, whitefly,
cabbagelooper, beet armyworm, leafminer.
||Tip burn from irregular moisture, or lack of
calcium; bolting, bitterness due to high temperature or lack
of moisture; leaf rots due to soil and/or water on leaves.
HARVESTING AND STORAGE
|Days to Maturity:
||40 to 80 days, depending on type.
||Leaf lettuce can be used as soon as plants
are 5 to 6 inches tall. Use the older, outer leaves which
contain high levels of calcium first. You may wish to harvest
every other one of the largest plants to accomplish thinning.
Bibb lettuce is matured when the leaves begin to cup inward to
form a loose head. The heads will never become compact. Cos or
Romaine is ready to use when the leaves have elongated and
overlapped to form a fairly tight head about four inches wide
at the base and 6 to 8 inches tall. Crisphead is matured when
leaves overlap to form a head similar to those available in
groceries; heads will be compact and firm.
Crisphead lettuce will keep about two weeks in the
refrigerator. Leaf and Bibb will store as long as four weeks
if the leaves are dry when bagged. If lettuce is to be stored,
harvest when dry, remove outer leaves but do not wash, place
in a plastic bag and store in the crisper drawer.
||5 to 10 pounds per 10-foot row.
|Amount to Raise:
||5 to 10 pounds per person.
||Cool (32° F), moist (95% relative
humidity) conditions for 2 to 3 weeks.
||Cool, moist refrigeration; canning and
freezing not recommended.