I would normally say that it's because of excessively hot dry conditions, but this is evidently NOT the reason that this week some of my young lettuces decided to bolt. In Fleet it has been wet, windy and much colder than you would expect in August. The rain has been torrential at times, night-time temperatures have sometimes been in single figures, and the daytime maximum temperatures have been in the region of 17 or 18. I suppose the poor old lettuces are as confused as we humans are by the vagaries of Climate Change!
When we say a lettuce has "bolted" we mean it has decided to run to seed prematurely. The lettuce produces a tall woody stem, (reaching a height of 2 or 3 feet) and the leaves go tough. New leaves produced are small and bitter. Eventually the plant will flower if you let it.
|A Cos lettuce that has bolted|
|A bolted "Yugoslavian Red" lettuce|
Once a lettuce has decided to bolt, there's not a lot you can do. The plant will not be nice to eat, so it's probably best to dig it up and put it on the compost heap, making room for something else.