They are native to North America and though most species are perennial, the most familiar species, the large flowering common sunflower (Helianthus annuus), is an annual. This species has been hybridized extensively and now there are lots of wonderful varieties with tremendous color variations available for the garden.
Many beautiful perennial Helianthus varieties are available as well. These are less well known and sadly, I think underutilized in our perennial gardens. My favorites are the very tall Helianthus angustifolius and the slightly shorter, but equally striking Helianthus salicifolius. Both of these species form robust clumps of attractive foliage that make a wonderful backdrop for other perennial flowers and some of the shorter ornamental grasses. The masses of dazzling golden yellow flowers that appear in September are almost neon in their intensity. They truly stand out from a distance!
Butterflies of all kinds find the masses of yellow flowers irresistible in the fall. Your garden will literally come alive with the flitting of these colorful visitors. Bees, too, enjoy the sweet nectar of the sunflowers.
There are many wonderful varieties of perennial sunflowers. A nice tall variety, Helianthus angustifolius 'Gold Lace' grows from 5-6 feet tall. This attractive perennial virtually "explodes" with vivid golden-yellow blooms in the early fall. A stunning addition to any sunny garden if you have the space! Need a shorter form? Helianthus salicifolius 'First Light' grows to a mere 48" tall! Shorter still is a new dwarf form, Helianthus 'Low Down', which tops out at only 12"-18" tall. There are many other wonderful cultivars available and they are all terrific in the garden.
Helianthus are easy to grow because they aren't too picky! They prefer full sun and grow best in moist, well-drained soil but they will tolerate a wide range of soil conditions except very dry soils. Sometimes the taller varieties need staking especially if they are not growing in full sun. To avoid this, they can be cut back by half or a third of their height in June. This not only keeps them more compact and bushy in the garden, but also improves flowering by allowing more flowering stems to be produced.
Helianthus are stunning when grown en masse in a large perennial border, although they produce such a profusion of blooms that even a single specimen in a smaller garden makes quite an impact! They combine well with ornamental grasses, asters, daylilies, Rudbeckia, goldenrods, Russian sage, coneflowers, and the vibrant blue late blooming Salvia azurea.