How can I improve germination rate at the summer peak temperatures? I will be planting radich.
Do you use covers? If so, what kind?
Whether you mean Radishes or radicchio, both are cool season crops, and growing is usually suspended during the summer months even somewhere like the UK. If you live somewhere very warm, it's best to wait until temperatures are lower before sowing seed of either, unless you have a chilled greenhouse in which to grow them from germination to cropping.
Sanjihan, have you provided any cover to block some of the IR from the sun? What are your temperatures? Shade cloth, 30%, seems to help very well with bolting on a few of my crops. I also have major fans blowing because up to a certain point, usually 90 degrees F, plants photosynthesize hugely producing lots of O2 that needs to be blown away from the leaves to allow CO2 to be used for photosynthesis so the plant can continue to function. Be nice to chill the greenhouse but usually just blocking some of the IR and using fans can help just as well. Eat them before they decide to bolt...either radishes or radicchio lettuces.