Lettuce has been a staple of the dinner table for a very long time. Drawings of lettuce have been found in Egyptian tombs dating back to 4500 B.C. but it is thought that the plant was used for the oil extracted from the seeds instead of for salad. Three varieties are mentioned in the 350 B.C. History of Plants and only the richest Romans were familiar with 12 different varieties. Charlemagne is credited with bringing the seeds of lettuce to France in 780 A.D. and seeds were brought to the New World by Columbus. Dutch and English settlers brought lettuce to the northern part of American and it traveled with French explorers to Canada. Lettuce was a common garden crop in Colonial times. At George Washington’s Mount Vernon, 16 beds of the mapped out 61 were for lettuce alone.
Lettuce grows well in fairly cool weather. Ideal temperatures are between 45 and 70 degrees and therefore, should be planted in either early spring or late summer. Lettuce will produce seed stalks and the leaves become bitter and stunted in high temperature. If this happens some will say their lettuce bolted.
There are basically 5 types of lettuce:
Leaf – the easiest and fastest to grow with leaves growing loosely on a stalk
Romaine (sometimes called Cos) – Forms an elongated, upright head
Crisphead – require most care and only grow in the north because of high sensitivity to heat (iceberg is the most popular)
Butterhead – small and forms loose heads with tender soft leaves
Stem (or asparagus lettuce) – commonly used in Chinese dishes and have enlarged seed stalks.
Leaf, Romain, and Butterhead varieties can be planted in the spring as soon as the soil is dry enough to rake. Two more plantings can be done at 10 to 14 day intervals and will last until the middle of June when it will begin to get too hot for it to grow. Plant again in late August or early September for a fall planting. Seeds are very small so the earth must be raked well before planting. Any large clods of earth will inhibit growth. The use of 5-10-10 fertilizer can be used, but always do a soil test prior to application. Lettuce seeds must be watered well in order for germination to occur then later for establishment of plants. These varieties can be started indoors under lamps and transplanted in warmer spring weather with limited success. In general, it is better to wait and plant in the ground as soon as the soil can be worked.
With most varieties, seeds should be planted ¼ to ½ inch deep in single, double or triple rows about 14 inches apart. A good rule of thumb is to place 10 seeds per foot. Leaf should be thinned 4 inches apart, Romain and butterhead 6 to 8 inches apart. Seedlings that have been thinned can be transplanted or eaten. If trying crisphead varieties, they should be thinned 10 to 12 inches apart. Seeds should be purchased every year as viability isn’t good after the year is over. Store seeds to be used in the fall in the refrigerator and then throw away those that aren’t planted. Lettuce prefers loose soil with a slight acidic edge of about pH 6.0 to 6.5.
Lettuce has very shallow roots. Because of this it should be cultivated very carefully or you could pull up plants. Frequent light watering will cause leaves to develop rapidly; however, overwatering can lead to disease and burning of the leaves. Beds should be kept moist but not soggy. Mulch can help keep the soil temperature cool and help lettuce grow better. Growing lettuce in the shade of taller plants like corn or tomatoes can help growth in warmer weather.
Click here to see the second half of the lettuce article in How to Cultivate and Harvest Lettuce
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