I have never had any luck growing head lettuce and having it form a nice tight head. Has anybody else tried it and what kind of luck did you have and what was your procedure?
I had some luck one year by planting a heat resistant type and using transplants instead of sowing directly into the soil. They just don't like it if hot weather hits before forming a head.
I haven't had much luck with head lettuce. But I have sown leaf lettuce mixtures that contained nice thick tight plants, almost like an elongated head lettuce.