Lettuce is a plant of the composite family which was grown long before the beginning of our calendar, by Persians as well as Egyptians and Greeks. Selective breeding for several thousand years of a common weed, barb lettuce (Lactuca serriola) is probably its origin. The Romans, who spread many vegetables across Europe, took over lettuce-growing from the Greeks. It wasn"™t just perpetual lettuce of various colours, but also lettuce heads, oblong loosely knit heads, so-called Cos-lettuce, named for the Greek island where the Romans found it, lettuce was used as both food and medicine. Our common head lettuce turns up during the Middle Ages and has, after a tentative beginning, become the most commonly grown lettuce, now together with the later kinds, iceberg- and Batavia lettuce.
Lettuce can be grown on most kinds of soil, but the best result comes from a humus-rich, loose and moist soil. It has an inordinate need for nutrients and access to phosphorus and potassium is far more important than nitrogen. The latter is the cause of big loose heads if it is present in excess. Lettuce is a plant for cool weather and warm, dry periods often cause it to get tip-burn on the leaves and interior rotting, especially if there is too much nitrogen in the soil, the ideal temperature is 16"“18°C.
It prefers an airy plot, yet out of the wind. It mustn"™t dry out and needs some shadow during hot, sunny days. It is a good idea to grow lettuce in the company of carrots, radishes, strawberries, cucumbers and onions, but not fennel or Thalictrum.
Attacks by insects are uncommon. Plant lice, if any, can be combated with repeated powerful showers of water, algomin, wood-ash, fresh nettle water, tea of common tansy or wormwood etc. During rainy periods the slugs can cause great damage. Control them by different traps, emptied every day and repeated sprinkling of lime, wood-ash, soot, rock-flour, algomin or salt.
To prevent and reduce attacks by fungi, which is a much greater threat to lettuce than the above, crop rotation is important. Most spores of mildew and rot are bound to the soil so spraying both soil and seedlings with extract of algae and/or tea of horsetail is efficient.
SOWING: Sow thinly about 0.5 cm deep! The seeds need light and a temperature below 18oC to germinate. A higher temperature causes late and bad germination. Lettuce can be forced very early in a green-house (soil temperature at least 5°C) or sown indoors and in hotbeds 3-5 weeks before handle several degrees of frost. Direct sowing can take place as soon as the soil is ready. Water the row before sowing if the soil is dry. That lowers the temperature some when sowing in high summer. To get a supply of lettuce all through summer and autumn, sow successively or several kinds of different growth times! Autumn sowing for wintering could succeed.
SPACING: Thin out early! Head lettuce, especially iceberg lettuce, need a mutual space of 25-30 cm to be able to form heads, other sorts need 20-25 cm, 35 "“ 50 cm between the rows.
HARVEST: The lettuce heads should be harvested as soon as they have made heads, perpetual lettuce gradually as the leaves grow or as whole fully grown plants.
SEEDS: 700-1100 seeds/g, a normal portion sows 5-10 m outdoors or yields 100-250 seedlings for setting and 5 g for 100 m if sowing directly and 20 g yield seedlings for 1000 m2. 50-100 g sows 1000 m2 directly.
(MTO)= the seed has been tested for mosaic virus.