Any areas of long grass where wildflowers have been established will be dried by now. The dead stems can collapse and smother seedlings and flowers so it’s wise to cut back the dead growth. It will also remove nutrients from the soil if you clear away the dead grass, which is beneficial to the flowers and will slightly weaken the grass. By now any seed heads will have shed their seeds and autumn rains will help these germinate, so a wider range of flowers should bloom next year.