Every single one of them has bolted.
Ironically, both of my two endive varieties are ones supposedly ideal for Summer cultivation. They are both ones I bought in France. I want to quote you some words from the packets. The variety "Chicorée Frisée de Meaux" says "...resistant bien à la chaleur et àla sécheresse", which translates as "...has good resistance to heat and dryness". The other one is "Caillard" which simply says "Pour recolte d'Été" (for Summer harvest). Hmmm.
I'm not giving up though. I have another lot coming on. Maybe they'll do better.
In fact, I have a third batch as well, though they seem to be fated too. I sowed the seeds thickly in some pots, and then thinned them out when they had formed their first pair of leaves. However, the day after I thinned them, one of the pots was decimated by birds (presumably pigeons), and then the second pot was attacked by slugs! Slugs and snails don't often go for Endives, on account of their bitter taste, but I guess sometimes they enjoy a change!
Still, I had enough left, so it wasn't a disaster. Nevertheless I felt that it would be a good idea to get them into the ground ASAP, so I have removed the bolted Endives and replaced them with a mix of young Endives and Lettuces of various sorts.
Over there on the left you can see my row of Spring Onions too (rather beaten down by recent heavy rain). I have never had much success with Spring Onions, but these ones don't look too bad. They are still very small, but doing OK so far, so you never know...
Prompted by the completion of this task, I also sowed a tray each of Radicchio and (more) Endives for growing in the Autumn. My successional sowing this year has been spot-on, hasn't it?!