I agree with Aunty about strong light discolouring the curds, so I always fold the leaves over as soon as I can see them developing. I just snap the outer leaves towards the centre. I grow mine under scaffold netting supported by hoops to keep out the butterflies, but last year when it was so hot for extended periods I also just threw another double layer of netting over the top to give shade and this worked. I removed the extra netting as things cooled down a bit. This year I've had really good, large, tasty caulis from Zaragoza, a variety I hadn't grown before, but I'll certainly do it again next year.