";s:4:"text";s:2969:" Butter lettuce, or butterhead, is one of the four main types of annual lettuce (Lactuca sativa) widely available in the … The leaves are colorful, mainly in the green and red color spectrums, with some variegated varieties. These plants are all so similar, however, that these tiny oblong radicchio heads can be used interchangeably with traditional white Belgian endive. Red Chard. Oak Leaf lettuce (Red/Green) Another loose-leaf lettuce, Oak leaf has very attractive serrated, deep-green leaves sometimes tinged with red. Lettuce is one of the most versatile and valuable crops to grow in a polytunnel in the UK. Additionally, this type of lettuce is an excellent source of beta carotene, which may be indicated in reducing risk for developing cataracts. It packs a high nutritional value, far superior to iceberg lettuce, into very few calories, about 15 per a 12-ounce (340.2 grams) serving. Lettuce's native range spreads from the Mediterranean to Siberia, although it has been transported to almost all areas of the world.Plants generally have a height and spread of 15 to 30 cm (6 to 12 in).