Who doesn’t adore black-eyed susans (Rudbeckia spp.) for their non-stop flowering and strong constitutions? Most cultivars sport bright shades of yellow and gold but tender varieties come in coral, rust, bicolors and even red. If you’re looking for long-lasting summer color to cheer you up, rudbeckia will do the trick.
Black-eyed (and brown-eyed, and green-eyed) susans are also commonly called coneflowers, a name that can refer to echinacea as well. To avoid confusion I’ll just call it rudbeckia here.
Rudbeckia comprises 25 species of North American native wildflowers in the sunflower family Asteraceae. Two or three in particular have been hybridized heavily and dominate the trade.They are fulgida and hirta, and to a lesser extent, laciniata.
While the flowers look similar, each species performs very differently in the garden, so it helps to know which is which. All have daisy-like rays surrounding a prominent cone, hence the “eye” in the name.
Fulgida and laciniata are hardy perennials. Hirta and its cultivars are tender outside of zone 9/ 10, acting like an annual or biennial, or even short-lived perennials (typically living 3 years). Then a few are genuinely biennial. Stay with me here– it gets confusing fast!
Let’s start with the perennials, cultivars you can count on season after season.
Goldsturm
You may already grow everyone’s favorite, rudbeckia fulgida var. sullivantii Goldstrum. A powerhouse of color, this cultivar (German for ‘gold storm’) is the most widely grown rudbeckia on the market today. It truly is a “gold storm” in bloom. Starting in July, Goldstrum produces a profusion of sulphur yellow flowers, covering the plant. Mass it, and you’re assured an ocean of color from midsummer on.
This is the ubiquitous black-eyed susan we’re most familar with, time-tested and well recommended, for anyone wanting to start out growing rudbeckia. You can’t go wrong with Goldsturm.
Goldsturm does well just about anywhere in full sun. It will also self-seed and spread readily unless you deadhead. At 20 – 24 inches with smooth, deep green foliage, it is a versatile must-have that flowers continuously for up to two months. Even in winter, after its dead growth has been cleared away, new shoots with baby leaves will emerge and stay semi-evergreen until really frost-killed.
Its only downside, as far as I can tell, is a propensity to develop blackened and marred foliage unless it has excellent air circulation. The petals may also get nibbled and ragged from slugs as the season progresses. Otherwise, it’s usually trouble-free.
Golden Glow, the “Outhouse Plant”
I’m old enough to remember when Golden Glow or Rudbeckia laciniata Hortensia was the only (cultivated) late-flowering yellow perennial available to rural gardeners in my area. Also known as Cutleaf Coneflower, it has graced many an outhouse along with hollyhocks and lilacs. At my childhood home it bloomed next to an old cistern where a windmill once stood. It’s still useful today for back of the border color, but unfortunately it is very susceptible to powdery mildew. Give it good air circulation and treat it with sulphur powder to help ward off mildew.
Henry Eilers (Rudbeckia subtomentosa Henry Eilers) also gets five feet tall and has unusual quilled petals. The massed effect is like looking at pinwheels!
Of course, not everyone can accommodate such tall choices.
Want something shorter?
Little Goldstar (Rudbeckia fulgida var. sullivantii Little Goldstar) might be just the thing. At ten to fourteen inches tall, its nearly dwarf size works nicely as a groundcover or edging. Its petals are thinner and the blooms slightly smaller than Goldstrum, but the display is still full. (Mine got nibbled after being open a while, but were still nice.)
Viette’s Little Suzy (Rudbeckia fulgida var. speciosa Viette’s Little Suzy) is a medium-compact variety reaching 18 inches tall. A versatile, strong performer that works well with many other flowers. A good choice for all-around performance. Notice the orangey coloring close to the eye.
That’s it for the most common perennial forms.
Rudbeckia hirta, a terrific native
The yellow wildflower often seen in fallow fields and roadsides, Rudbeckia hirta is indigenous to all fifty states and Canada. This tender yet resilient species has a hairy basal rosette with sparsely arranged leaves arising on wiry stems. Its blooms look very similar to Goldsturm, but that’s where the similarity ends.
Hirta is actually a tender perennial that behaves like an annual or biennial outside of zones 9/ 10. Occasionally it may survive as a short-lived perennial. While hirta is perfect for meadows and informal borders, it’s not the best choice for color blocks. It has an airy habit and typically tops out at 30 – 36 inches. I use it on my bank along with other natives. It’s been remarkably trouble-free for me, except for the deer — they love to browse the foliage, unfortunately, and constantly eat it down to nubbins. So perhaps skip it if you get deer visiting regularly.
Most hybrids have hirta in their parentage, presumably for its superior disease-resistance. That means they behave as either biennial or annual in colder zones. So be forewarned: They are not going to last multiple seasons.
(Lesser-known native species like triloba and ratibida are better suited for western and xeric landscapes; I don’t recommend them for Pennsylvania, so I’m not covering them here.)
Annuals, Biennials and Tender Perennials
Hirta hybrids are often called Gloriosa Daisies, which can be annual or biennial. I’m sure you’ve heard of Gloriosas. Most nurseries carry multiple varieties. Here are just the most popular cultivars.
Indian Summer is a biennial or short-lived perennial that performs superbly in our heat and humidity. It’s big in every respect: size, color, substance. At 24 to 30 inches tall they rival daylilies with their heft and presence. Because the color is intense and the flowers are 4 to 6 inches across, one plant is often enough! Mix these in with cool white, blue or purple companions to balance the screaming hot color.
Sahara is a pretty double that comes in a mix of copper, pink, pale red, burgundy bicolor, and yellow. These frilly beauties resemble calendulas. Sahara is billed as “half-hardy annual” which simply means it’s going to behave like an annual in most zones, so don’t expect it to over-winter.
Cherry Brandy is a two-foot tall Gloriosa with stunning 4-inch red blooms and a chocolate eye. Pretty with burgundy foliaged companions or variegated green-white shades, such as heuchera or euphorbia. An interesting selection that would offer amazing cut flowers! Treat it like an annual.
UPDATE, Summer of 2023: I planted a single Cherry Brandy plant that I purchased from a local nursery. I was very disappointed. Poor, stunted growth and faded looking color was the result, not at all like the photo below. Based on this experience I can’t recommend it. Sorry!
Other “short-lived” Gloriosas include Chim Chiminee, a 30-inch variety with quilled petals; Cherokee Sunset, a 24-inch double in burnt sienna tones; and Prairie Sun, a 30-inch green-eyed bicolor in orange and lemon. The latter two are very similar to Indian Summer with large, 4-inch blooms on very robust plants.
Fresh and neat looking! Expect these to last anywhere from one to three seasons.
Growing Rudbeckias
As noted earlier, the biggest problem with rudbeckias is their susceptibility to powdery mildew. Most hybrids are much more resistant than the older varieties, but any of them can succumb. It all depends on the weather.
To keep mildew at bay, ensure good air circulation and water regularly during dry periods, but don’t over-water. Rudbeckias prefer things on the dry side. (You may still get mildew no matter what you do.) Mildew normally won’t kill the plant, but it can affect vigor.
The other caveat is not to fertilize. Rudbeckias prefer nutrient-poor to average soil. Clay is fine, and so is a slightly alkaline or acidic ph. By and large the less you do, the better they thrive. Deadhead to prevent self seeding. Otherwise, cut the whole plant to the ground in fall, and transplant any newly emerged baby plants in early spring if desired.
So now you know why Gloriosa daisy lifespans are frustratingly short, and which cultivars you can count on year after year. I hope you make room for a few of these color machines. You’ll be glad you did!
The only reason Rudbeckias are not a five-star plant is that so many cultivars are short-lived, and their issue with mildew.
