Get It Growing for 09/25/26

If you take a drive down the highways and byways of Louisiana in the coming weeks, you might notice large masses of golden-yellow flowers on the side of the road. This very likely is Helianthus angustifolius, better known as the swamp sunflower.

Native to Louisiana and much of the United States, swamp sunflower is one of our most reliable flowering perennials. It blooms from early to mid-fall, peaking in October.

This plant will grow almost anywhere. It favors wet environments — such as the roadside ditches where it’s so often seen this time of year — but is highly adaptable. It’s an outstanding performer in both natural settings and home gardens, where the towering plants work well in the back of beds.

Swamp sunflower’s daisylike flowers typically measure 2 to 3 inches across — smaller than the blooms you’ll see on the common sunflower (Helianthus annuus). Their yellow color is just as cheerful, however, and they’re highly attractive to seed-loving birds and pollinators seeking nectar and pollen.

A couple of other features distinguish swamp sunflower from other sunflowers. Instead of a single flowerhead at the top of a stalk, swamp sunflower stems tend to be branched and display multiple flowers. And its foliage is strappy, almost needlelike, with a rough texture.

Swamp sunflower can reach 6 to 8 feet tall, sometimes even more. It looks its best and puts on the most blooms when grown in full sun. In the shade, plants become leggy.

Propagation is easy. If you look at the base of swamp sunflower plants, you’ll likely see a number of plantlets emerging. You can divide these from the mother plants in late winter or early spring to plant in a new area or to share with friends.

Swamp sunflower also is a prolific seed producer, a trait that allows it to regrow year after year in nature. If you want to collect the seeds to plant in a specific location, cut off mature flowers and allow them to dry for a few days. Then, shake out the seeds and store them for planting. Like many native perennials, planting the seeds in late fall or early winter is best.

Learn about swamp sunflower with LSU AgCenter horticulturist Jason Stagg.

Swamp sunflower’s golden-yellow flowers appear from early to mid-fall in Louisiana. Photo by Olivia McClure/LSU AgCenter

Pollinators are attracted to swamp sunflower blooms. Photo by Olivia McClure/LSU AgCenter

Swamp sunflower plants grow quite tall, typically reaching 6 to 8 feet. Photo by Olivia McClure/LSU AgCenter

A bee visits a swamp sunflower plant. Photo by Olivia McClure/LSU AgCenter