Plants range from 6 to 50 inches tall and have bristly oval leaves. The large-flowered zinnias are the ones that capture most gardeners' fancies. These big bloomers benefit from deadheading, weekly if possible, and may need staking for extra support. They resist common foliar diseases and tolerate heat and drought. Growing in loose mounds and reaching 8 to 18 inches tall, they can serve as annual ground covers, and are also attractive in hanging baskets or at the front of a border.
Interspecific crosses are low-maintenance zinnias that have been introduced over the last decade.
They combine the flower colors of garden zinnias with the durability of spreading zinnias. The Pinwheel series now includes flowers in gold, orange, pink on white, and white. They grow about 15 inches tall, covering the old flowers with new leaves and buds, and thus eliminating the need to deadhead. Small zinnias make good edgers for summer annuals, filling in after spring pansies. I particularly like 'Rose Border Beauty' with 'Purple Wave' petunias.