Lettuce (Lactuca sativa) is a temperate annual or biennial plant of the daisy family Asteraceae. It is most often grown as a leaf vegetable. It is eaten either raw, notably in salads, sandwiches, hamburgers, tacos, and many other dishes, or cooked, as in Chinese cuisine in which the stem becomes just as important as the leaf. Both the English name and the Latin name of the genus are ultimately derived from lac, the Latin word for “milk”, referring to the plant’s milky juice. Mild in flavour, it has been described over the centuries as a cooling counterbalance to other ingredients in a salad.
Lettuce plants should be grown in a light, sandy, fertile, humus-rich soil that will hold moisture in summer. A soil pH of 6.5 is preferred (this slight acidity in fact goes against the common ph nature of the aquaponic system, but it is interesting to note that lettuce has been grown aquaponically throughout the years. so the acidity itself sometimes is not that critical.); lime may be added for this purpose. For best eating quality, water is essential; the plants prefer the soil to be moist at all times.
- ph = 6.5
Lettuce plants prefer cool weather, ideally with day temperatures below 75 degrees Fahrenheit (this is asbout 25 C, ok for fish of most kinds) and night temperatures above 40 degrees Fahrenheit. Hot, sunny, or dry conditions may cause the plants to turn bitter and produce a flower shoot, a process known as bolting. Therefore, lettuce is often grown in the coolness of spring and autumn in the Northern Hemisphere; lettuce sown in summer is often grown in light shade. In addition, bolt-resistant summer cultivars of lettuce may be recommended as temperatures increase.
- temp = 25C
Lettuce can be direct sown in the garden, but lettuce plants are often started in cold frames or greenhouses, and the resulting seedlings transplanted to the garden or field. This allows an earlier start, or allows more efficient use of garden space, (but of course this assume labor cost is less than the space cost as the case in China) as the lettuce can be transplanted when growing rapidly, avoiding the use of garden space for germination of seeds.
- seedling is slow, so only grow more mature lettuce in the commercially precious field. in fact this shuld be the best practice for most plants, it is common that germination takes time and farming space should be saved only for the last stage of the growing.
As another way to allow an earlier crop in cold weather, lettuce is sometimes given glass protection, known as a cloche, or protected with spun material known as a floating row cover. In sufficiently mild-weather climates, these same protective devices (greenhouses, cold frames, cloches, row cover) may be used to protect lettuce throughout the winter, allowing harvest even in near-freezing or freezing weather. Lettuce is hardy to Zone 6.
Lettuce is often grown between rows of slower growing plants like brussel sprouts or broccoli. This is called a catch crop. It allows more efficient use of garden space, and also provides the lettuce with needed shade in warm weather.
try to avoid this – lettuce bolting –