Many times in this column we’ve taken a look at unusual plants that you’ve possibly never heard of, in the hopes you might find them to worthy of consideration for your garden. This month, however, we’ll talk about a plant that almost every one is familiar with, the black-eyed Susan, Rudbeckia hirta.
Rudbeckias get their name from Olaus Olai Rudbeck, a Swedish physician with a botanical interest. The genus Rudbeckia is native exclusively to North America, although the black-eyed Susan has naturalized in China. Although Rudbeckia hirta is indeed a common wildflower, there are many other species and varieties that are less well known.
First, a closer look at R. hirta. It’s commonly referred to as the black-eyed Susan, even while other members of this genus may also be called by that name. To add to the confusion, the Rudbeckias are also sometimes referred to as coneflowers, although I prefer to apply that name to the Echinaceas, especially the purple coneflower, E. purpurea. In hopes of avoiding even more confusion, I’ll refer to species by their scientific names, as well as by their common names.
If you’re thinking about buying a R. hirta plant, you might want to reconsider. According to various sources, it’s referred to as an annual, a biennial, or a perennial. Take your pick, although most people come down on the side of annual. Allan Armitage, retired from the University of Georgia and author of Herbaceous Perennial Plants, opines, “regardless of claims to the contrary, they should be treated as annuals.” Which certainly doesn’t mean that they won’t come back from seed in your garden.
If you want something more colorful than the ordinary R. hirta, the Gloriosa Daisies are definitely flashier. Sometimes considered to be varieties of R. hirta, they may actually be hybrids of uncertain ancestry. Their larger flowers typically have splotches of orange or russet toward the center. One source touts them as the “perennial form of black-eyed Susan,” but, hey, you have been warned. (See Armitage, above.)
Notwithstanding all these caveats, there are truly perennial Rudbeckias out there. Native to the eastern and central U.S., the Orange Coneflower (R. fulgida) grows to about 30”; flowers are really more a golden yellow than the orange that the name implies. Most commonly seen is the cultivar ‘Goldsturm’, with thick dark green leaves and 3-4” deep yellow flowers that appear from late July well into September. Reportedly deer-resistant, ‘Goldsturm’ spreads by both rhizomes and seed. Dividing the clump every few years will keep the plant healthy and prevent a hostile takeover of your garden.
Being inordinately fond of tall perennials, there are a couple of vertically-enhanced Rudbeckias that have found a place in my garden. (And tall perennials do have a place in the garden, serving as exclamation points in what could otherwise be a monotonous swath of shorter plants.) Cutleaf coneflower (R. laciniata) is clothed with deeply incised leaves that are reminiscent of those on a scarlet oak. The species may grow only to about three feet, but the cultivar ‘Herbstonne’ can reach seven feet. The light green, very faintly striped stems are topped with 3” flowers with drooping yellow petals; the central disk is green, rather than the typical brown or black eye of other Rudbeckias.
Another tall Rudbeckia is the Giant Coneflower, R. maxima. In addition to its seven foot height, the Giant Coneflower—which could be referred to as Rudbeckia-On-a-Stick—is known for its distinctive powder-blue-green foliage. The basal clump’s paddle-shaped leaves can be up to a foot long and eight inches wide, but become increasingly smaller and sparse toward the top of the stem. The yellow flowers develop a two-inch tall “cone” at their center as they ripen. The other day I noticed a couple of goldfinches checking them out.
Tall Rudbeckias can flop somewhat in strong winds or heavy downpours. You can counteract this by staking, a somewhat tedious process, or by using grow-through supports. (I hope to try those next year. By this time of year it’s too late to install them.) Alternatively, planting your Rudbeckias or other tall perennials near sturdy shrubs can give them some friends to lean on.
In the last few years some interesting Rudbeckia x Echinacea hybrids have come to market. Called EchibeckiasTM, they purportedly provide the color and fast growth of the former genus and the hardiness of the latter. They’re available in cultivars such as Summerina Brown, really more of a russet color, and Summerina Yellow. I’ve had mine in the ground only a few weeks, so the jury is still out. The rabbits seem to like them, however.
Rudbeckias as a group prefer full sun and average to moist soil conditions, but generally tolerate drought. The foliage on R. laciniata in my garden droops in mid-day heat, even with abundant soil moisture, then perks up when the sun moves on.
From a design perspective, Rudbeckias—as well as many other wildflowers—show best in a bed mimicking a prairie, with native grasses inter-planted. Cultivars of Panicum virgatum, namely ‘Shenandoah Red’, ‘Northwind’ or ‘Cloud Nine’ would be good choices. To take in such a planting might give a hint of the pre-European American tall-grass prairie in its high-summer glory.