From Master Gardener Jeff Daley: I love when the garden comes to life around the end of summer and is full of summer annuals at their peak of growth. Among perennial plants, one in particular is my poster child for versatile late-summer flowers: Rudbeckia, the black-eyed Susan. This North American native plant from the sunflower family is a beautiful ray of sunshine in the garden. It's one of my favorites, not only because of its distinctly bright yellow color, but also because it is a consistently reliable performer in the garden.
As you walk around campus, know that all the Rudbeckias you see originally came from only four flats of plants just a dozen years ago. This is a plant that can be easily divided and transplanted throughout your garden. Dividing them every spring can get you free plants to place everywhere, a cost-effective way to add beauty to the garden.
Being a late summer bloomer, Rudbeckias provide many pollinators their last bit of pollen and nectar before the leaves start to fall and we head into autumn. If you leave the flower heads on the plant, it will attract birds that come to eat the seed in early winter.
There are several varieties of Rudbeckia. What we have on campus is primarily Rudbeckia fulgida "Goldstrum," a great stand-alone perennial variety you can count on to return year after year.
At home, I grow the Rudbeckia hirta varieties. They are mostly an annual plant that produces by seed. If the winter is mild they might continue. With this variety, not only do you get a brilliant yellow color like the Goldstrum variety, but also some orange and rust-colored hues in the petals. It's fun when these flowers cross-pollinate because the seeds that germinate can turn into wild, new flowers you won't see in a nursery. Hirta varieties also have big double flowers that are absolutely gorgeous!
If you're looking for a taller variety to plant in the back of your flower bed, Rudbeckia herbstonne is an upright, clump-forming knockout that will grow from 5 to 7 feet tall, and 2 to 4 feet wide. This is the granddaddy of them all!
Rudbeckias will be happy in just about any sunny location with well-drained soil. They will tolerate drought better than they will overly moist, soggy soils. However, supplemental water during our dry months will be important. Choose a spot in the garden where your plants will receive ample air circulation, and try not to water directly on the leaves in the evening to avoid the development of powdery mildew that can form on the leaf surface.
Black-eyed Susans bring a dash of sunshine yellow outside as well as in the home. Consider adding them to a bouquet or cut flower arrangement for a touch of summer in your everyday life. (Select the link to see Rudbeckias around campus.)