I am not sure if you plan to use only wild flowers in your cutting garden or will accept others as well. This list of suggestions is far from complete, but will give you a start. Flowers such as roses and peonies can be dried of course, but are somewhat more difficult to handle. Flowers can be dried by several methods, including air-drying (the easiest), using a dessicant such as borax or "Flower-Dri", and with glycerine (usually used on leafy branches and woody plants. Ornamental and roadside grasses, yarrows, amaranthus, pearly everlastinng, artemisias, cock's comb and other celosias, globe thistle, baby's breath, strawflowers, thrift, annual statice, and salvias are all good candidates.