Try to figure out why all my lettace bolted

[dirtclod]

Three Spring and Fall plantings in diffterent areas. The only thing in common was the seed. But I can't rule out a soil condition...I just don't know what. All the other cold crops that produce heads (brussel sprouts and cabbage) did fine. The lettace started getting purple fringes on the leaves while still small. I read somewhere this is a sign it will bolt - but they said blue, not purple (maybe their color vision was off) but didn't specify a cause except heat. Heat has not been a problem on two of my plantings. I thinned them in a timely manner but they bolted anyway. Any ideas?

BTW - the variety is iceburg from Bunton Seeds.

[pharmerphil]

Iceberg lettuce will bolt if the temperatures gets over 70 degrees for even a few days.
best to spring/fall plant only
and lettuce; any type, does not need full sun, you can plant in the shade of taller crops to protect it from direct sun, or plant in an area that only gets morning sunlight
you can plant varieties that are more heat tolerant and slower to bolt, try Black Seeded Simpson, Salad Bowl, Little Gem or Red Sails.
Even here in Minnesota, we have pretty much given up on headed varieties.
because it will go from Brrrr cold in the spring, to 90° in a days time

[jal_ut]

Lettuce likes cool weather. Plant early in the spring. I like to plant 3 or 4 seeds in a group each foot in a row, then when it comes up, thin the bunch to one plant. If you give lettuce some room like this, it will make a nice head. I always plant lettuce in full sun.

Hot weather, the time it has been growing, the fertility of the soil, the available water, the length of day, all have a bearing on when the plant will bolt. This is the natural thing for the plant to do. Bloom and make seed. You want to encourage good early growth so it will make a nice head before it decides it is time to bloom. Plant early in fertile soil, keep it damp, and give it room to grow and you will succeed.

Edit to add: try some of the leafy type lettuces. Black-seeded Simpson, and Romaine are my favorites. Thin these just the same as above.