We prefer the smaller, white “salad” turnips. We eat them raw or sometimes cooked. Although we’ve grown the normal purple tops too. We have better luck sowing in spring, a shorter season type, then in later July - avoiding the really hot part of the summer. Try sowing in succession too, like you would for a radish- that way you have them at the just-right size for a longer period. They can handle some shade too,I "WILL" master turnips this year