by David Hillock • agriculture.okstate.eduVegetablesYou have all of September to plant cool-season vegetables like spinach, leaf lettuce, mustard and radishes, and until the middle of September to plant rutabagas, Swiss chard, garlic and turnips.FlowersPlant cool-season annuals like pansies, ornamental cabbage or kale, snapdragons and dusty miller when temperatures begin to ...