Answer: I'd pinch them off. It is normal for the oldest leaves to turn yellow and die. Your cucumber plant is putting its energy into producing healthy new leaves at the ends of the vines, and it is flowering and producing fruit. The oldest leaves are not needed as much as the newer leaves. I'd cut them off. Water your plant deeply twice a week during the hot weather and they should be fine.
Best wishes with your cucumbers!
Q&A Library Searching Tips