WATCH: Here Come the Sunflowers
Autumn's prettiest perennials strut their stuff
Every October brings a patch of cheerful sunlight to Grumpy's garden in the form of a native perennial called swamp sunflower (Helianthus angustifolius). No, Grumpy doesn't live in a swamp, although the 60 inches of rain so far this year sometimes make it feel that way. Swamp sunflower gets its name because it grows in boggy soil, but it doesn't need it. It does just fine in regular garden soil with normal moisture and plenty of sun.
Faithful readers familiar with this plant know that it comes with two problems. First, it spreads quickly by roots in moist soil and can take over. Second, it can grow 10 feet tall. Solving these problems is easy, though. Here's how.
In spring, you'll see a number of new stalks growing a foot or two away from the original clump. If you leave them, you'll soon have a big patch of swamp sunflowers. Don't want a big patch? Then just grip an unwanted stalk at its base while the soil is moist and yank. It'll come up easily. Toss it in the compost or share it with a gardening friend. Swamp sunflower makes a good passalong.
Controlling the height involves nothing more than cutting back the plant twice during the growing season. When it reaches three feet tall, cut it back to two. Then when it reaches four feet tall, cut it back to three. That's it – no more cutting. By fall, it will have topped out at 4 to 5 feet. An added benefit to the cutting is that each trimmed stalk branches into two stalks at the point of the cut. Each stalk produces clusters of bright yellow flowers about two inches across. So you get many more flowers. Pollinators love them. After the flowers fade, cut the plants to the ground.
Swamp sunflowers look great combined with other fall bloomers such as blue and purple asters, Mexican bush sage, forsythia sage, old-fashioned mums, goldenrod, pink muhly grass, and Japanese anemone. Deer don't eat it and I never fertilize or spray it.
If you can't find swamp sunflower in local garden centers, Digging Dog Nursery is a good online source. Order only one! That's all you need.