"Coneflower" is a common name, and it has been applied to many different plants. Flowers from three genera, Echinacea, Ratibida and Rudbeckia, are called coneflower, and there are many species in each genus. Some of them are wildflowers, while others are cultivated as garden plants. They are called by the same common name because they have similar flowers, and they all flower from late summer into fall.
All coneflowers have a flowerhead with a round central disk surround by long, thin petals. The petals stretch out in a circle, forming a ray pattern similar to that of a sunflower. The disk is usually black or dark brown; it can be flat or columnar in shape. The color of the ray is different in each genus.
Although the flowerhead of a coneflower looks like a single entity, it is actually a cluster of tiny individual flowers. Each tiny flower in the central disk is pollinated individually and develops its own individual seed.
Echinacea purpurea, commonly called purple coneflower, is a perennial. The flowers in the species are a light blue-purple, but both red and white cultivars are available commercially. According to an article from Purdue University’s Department of Horticulture and Landscape Architecture, Echinacea purpurea "Magnus" was named perennial of the year by the Perennial Plant Association in 1998.
Plants in the Ratibida genus are commonly called prairie coneflower. The flowerhead disks in this genus have a columnar form. The rays can be yellow or brown, and they curve back from the disk toward the stem of the plant. Ratibida columnifera "Mexican Hat" is available commercially and is a garden favorite in the American Southwest.
There are many species of Rudbeckia, all called coneflowers or black-eyed Susans. They can be perennials, annuals or biennials, depending on the species. These coneflowers have flat black or dark brown disks and bright yellow or orange rays. Many cultivars are available commercially, but "Goldsturm" is the best known. It was named perennial of the year by the Perennial Plant Association in 1999.
In recent years, plant breeders have been developing new types of Echinacea to grow in the garden. A wide range of flower colors is now available, with over 30 cultivars on the market. These new cultivars are more expensive than the original Echinacea plants, because they are propagated by tissue culture in laboratories. This is the fastest way to make new plants widely available to gardeners. Otherwise, nurseries would have to wait several years until the first plants were large enough to divide and sell.