Dahlias, with their strong stems, long-lasting blooms, and substantial, attractive foliage, make striking cut flowers. Through centuries of hybridizing and selection, dahlias have become tremendously diversified, available in numerous flower types and flower sizes (from 2 to 12 inches across) and all colors but true blue. Pictured: Dahlia ‘Jitterbug,’ available through Swan Island Dahlias, dahlias.com.