Plant type: Tall, late-blooming perennial
Hardiness: USDA Zones 6 to 9
A relative of the annual sunflower, this perennial sunflower has smaller flowers but blooms for a longer period of time. Golden-yellow blooms cover this plant in late summer into fall. Blooms are daisy-like with yellow-black eyes and are two to three inches wide. The narrow, deep-green leaves with burgundy stems are coarse to the touch. Salt tolerant; good for coastal regions. Mature size is six to 10 feet tall, four to five feet wide. Native to the U.S.
How to use it: In masses or as a specimen plant, the swamp sunflower is prized for its stature. Use in the back of a mixed perennial border. Also good in a wildflower garden, a bog garden or native wetland plantings.
Culture: Swamp sunflower prefers a moist site in full sun to partial shade. If grown in shade, plants aren't heavy bloomers and tend to get leggy and fall over. Good for boggy or swampy sites. Will tolerate dry conditions if provided with enough hand watering. Also tolerates a variety of soil types. When planting, space plants about 12 to 18 inches apart. To produce bushier, more compact plants that will not lodge, cut back by a third in June. Dies down to the ground after a good freeze. Cut back dead stems to about six inches tall. Primarily propagated through seed and division. No serious pest or disease problems; can be susceptible to powdery mildew and spittle bugs.
Special Notes: Valued for its late blooming golden yellow flowers, salt tolerance, ability to grow in dry to waterlogged conditions, and verticality in the landscape. Attracts native butterflies, bees and birds. Deer resistant. Tolerates swamp and salty conditions. This plant is a threatened plant in native areas in New York and Illinois.
Warning: In ideal conditions (full sun, rich soil and enough water), swamp sunflower may spread by underground rhizomes and be potentially invasive.