This is called bolting . It is a sign your plant is done with being harvested and is devoting its remaining energies to setting seed to carry its genetics onto the next generation . In most species of lettuces , leaves develop a bitter taste once the plant begins to bolt . It is best to remove these plants from the hydro system and start anew . Lettuce is a cool-weather crop and as such will bolt when the temperature gets too high or the hours of daylight are too long . It does best in temperatures below 70 ° F ( 21 ° C ). To slow down the onset of bolting , a shade cloth should be put up if grown in sunny areas or the grow lights should be adjusted if grown using artificial lighting . Eventually , all lettuce plants that are not harvested using the whole-head method will bolt , but by reducing the amount of light shining on your crop , it will slow it down to prolong harvests .
” So long as the root system is healthy , and the hydro system is circulating enough nutrients , the plant will regenerate .“
For continual loose-leaf harvests , several plants should be seeded at regular intervals . The amount and frequency will be dictated by space constraints as well as how much lettuce is wanted . However , it is possible to harvest fresh lettuce leaves every week by seeding new plants every two to four weeks and alternate the harvest on the mature plants . Another method of harvesting leaf lettuce is similar to head lettuce in that the entire plant is harvested , but unlike head lettuce , the roots remain in the hydro system . Not all types of lettuce are suitable for this type of harvest , but many are . Butterhead and romaine types do typically grow back well after the initial harvest , but many other varieties also do well . Those that do are sometimes referred to as cut-and-come again lettuces . With this method , the lettuce is cut down to about one inch above the roots . So long as the root system is healthy , and the hydro system is circulating enough nutrients , the plant will regenerate . Cut-and-come again types will have a second full flush of leaves , though not always quite as full as before the first harvest . Once they have achieved harvestable size , they can be cut again , down to about one inch . A third flush of growth should follow . It should be expected to not be as full as the first or even the second but should produce enough leaves of sufficient size for a third harvest . Not many types will generate enough for a fourth or even fifth harvest , and it does not always make fiscal sense to keep nurturing them along past their prime when younger plants will provide greater harvests .
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Maximum Yield