Perennials: Rudbeckia

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‘Little Goldstar’

In 1999, the Perennial Plant Association chose ‘Goldsturm’ rudbeckia (Rudbeckia fulgida var. sullivantii ‘Goldsturm’) as Perennial Plant of the Year. It was an ideal candidate—simple to grow and care for, adaptable to nearly every part of the United States, and profuse-blooming with a compact, garden-friendly habit. Not new by any means, ‘Goldsturm’ was discovered in 1937 at a nursery in the Czech Republic.

For decades, ‘Goldsturm’ was the gold standard in garden rudbeckias. Sadly, just a few years after being named perennial of the year, a perfect storm of problems began to unfold for ‘Goldsturm.’ Three diseases—Septoria leaf spot, angular leaf spot, and downy mildew (different than the much more common and benign powdery mildew)—began to disfigure ‘Goldsturm’ plantings everywhere. The plants, which once provided great swaths of golden color, became masses of ugly foliage, marred by patchy purplish-brown spots that coalesced to encompass entire leaves. Flowering was diminished by the downy mildew, which, in addition to causing foliar lesions, also resulted in stunting and deformation of flower buds. To add insult to injury, an insect (rudbeckia psyllid) started to show up more frequently. Its nymphs feed on the underside of the leaves, resulting in the development of large purplish raised patches on the upper leaf surfaces.

So serious was this trifecta of diseases

(plus an insect) that nursery growers and gardeners found it nearly impossible to grow good specimens of a plant that for decades had been lauded as a top garden performer. In fact, my nursery made the difficult decision in 2008 to remove and destroy all ‘GoldKaren Bovio sturm’ plants, both in nursery pots and in our gardens, in an attempt to eliminate the spores and overwintering insects from our property.

Oddly for an American genus, the name honors the Swedish botanist Olof Rudbeck (1630-1702) and his son Olof Rudbeck the Younger. The genus was named by Carl Linnaeus, the younger Rudbeck’s very famous student.

Rudbeckias are sometimes referred to as coneflowers, and at one time, the genus Echinacea (aka coneflower) was included within the genus Rudbeckia. Their close kinship can be seen in the new intergeneric hybrids (Echibeckia) that are now making their way into garden centers. Be aware that this new man-made genus is comprised exclusively of annuals (non-hardy perennials) at this point.

Eric Hofley / Michigan Gardener

‘Indian Summer’

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‘American Gold Rush’

As research into the devastating rudbeckia diseases progressed, plant breeders took notice of the characteristics that imparted better disease tolerance. Rudbeckia selections with narrow, softly hairy leaves were typically more resistant.

Growers and breeders also took a closer look at older cultivars—the 15- to 18-inch, narrow-leafed variety ‘Viette’s Little Suzy’ (R. fulgida var. speciosa) stood out—and started working in earnest to develop more ‘Goldsturm’ replacements. They also sought to deliver more options in regard to height and habit. ‘Little Goldstar’ (R. fulgida var. sullivantii) arrived in 2011 and filled the niche for a truly compact fulgida-type rudbeckia. It stays under 16 inches with equal width, and its narrow, dark green leaves are practically disease-free. In 2020, All-America Selections named the rudbeckia ‘American Gold Rush,’ a recent hybrid with more complex parentage, as an AAS winner. It forms a profuselyblooming dome, 24 inches tall by 44 inches wide, composed of narrow fuzzy leaves that show no signs of foliar disease.

Although the Rudbeckia fulgida varieties exemplify the quintessential black-eyed Susan look, there are many other good rudbeckias for the garden. These other species round out the usefulness of the genus, with different growth habits, flower colors and shapes,

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‘Herbstsonne’ (‘Autumn Sun’) continued from page 15

and site preferences. The genus is comprised of 25 to 30 North American species, with a half dozen or more figuring prominently as garden plants.

The humble meadow wildflower commonly known as black-eyed Susan is R. hirta. The name means “hairy,” which describes its somewhat bristly leaves. The true species has simple, golden daisy flowers with the traditional black eye, and grows in fields as a shortlived perennial or biennial. But it is the R. hirta hybrids that are the most garden-worthy.

Gardeners should, however, be somewhat leery of the claim that these hybrids are perennials. They often fail to return after a typical Michigan winter, although they may selfsow. The ease with which they can be grown from seed has led to their extensive use as bedding plants. They may be sold in garden centers in packs or small pots, but due to their substantial size, you are more likely to find them offered in one-gallon or larger containers, misleadingly placed on nursery shelves alongside the true perennial types.

Nonetheless, R. hirta hybrids are beautiful garden plants and are available in a wide range of colors: traditional gold with a black eye (‘Indian Summer’), gold with a pronounced dark eyezone (‘Denver Daisy,’ ‘Sonora’), burgundy red (‘Cherry Brandy’), yellow with green eye (‘Irish Eyes,’ ‘Prairie Sun’), russet shades (‘Cappucino,’ ‘Autumn Colors’), as well as mum-like double forms (‘Cherokee Sunset,’ ‘Maya’) and quilled-petal types (‘Chim Chiminee’).

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Rudbeckia hirta hybrids are available in many heights, from dwarf 12-inch varieties, to tall three-footers. They look best from June through about mid-August, after which they may suffer from powdery mildew and decline quickly. In my experience, the only remedy is the early institution of a regular anti-fungal spray program, along with attention to proper watering needs—stress really increases powdery mildew susceptibility.

R. laciniata (aka green-headed coneflower) is a native to all but three of the western U.S. states. A five-foot tall plant with dissected leaves and true yellow flowers with green cones, it is found in the wild in moist soil meadows and along streams, growing in sun to partial shade. It and its naturally occurring double form (var. hortensia) are perhaps best left in the wild, due to their extremely aggressive rate of spread.

The double form, which bears fluffy yellow flowers, has been tamed somewhat in the variety ‘Goldquelle,’ which stays shorter at about three feet tall. It has a somewhat less rambling habit, although it suffers from floppiness due to the weight of its big flowers, in the same way that large double peonies flop after a rain.

A better choice, by far, is the hybrid ‘Herbstsonne’ (aka ‘Autumn Sun’ in English), which is most likely a cross of R. laciniata and R. nitida. This is a flawless selection and perhaps one of the best rudbeckias in cultivation, regardless of species or type. The plants are large and substantial, with broader, glossier dark green leaves and sturdier flower stems than its parents. Each stem is topped with many large single, canary yellow daisy flowers with green cones. The flowering display lasts from mid-July through September. Best of all, it has a clumping habit, rather than spreading. Expect plants to attain a height of at least 5 feet, with a clump width of 4 feet.

When not in flower, many gardeners would not recognize this plant as a rudbeckia. Its broad, waxy, blue-green leaves are unlike those of any other rudbeckia. The fanciful, descriptive common names Dumbo’s ears and cabbage-leaf coneflower provide clues to its appearance, although most wildflower references simply call it great coneflower. It has very large yellow flowers with drooping ray florets, borne singly atop leafless, arrowstraight stems up to seven feet tall. The dark brown cones elongate as they mature and are filled with large seeds that goldfinches adore. Great coneflower is adaptable to many soils and can even tolerate flooded soils for short periods of time, along with alternating periods of drought, making it a good candidate for a rain garden.

Eric Hofley / Michigan Gardener

‘Henry Eilers’ continued from page 18

This midwestern native is seldom used in gardens. It doesn’t have any particularly outstanding characteristics to make it worth the space it would take, unless perhaps used as a specimen in a native planting. However, two variants of the typical form are sought and used by gardeners for their very unique flowers.

The first was discovered by plantsman and naturalist Henry Eilers, growing along a stream bank in south-central Illinois. Rather than the typical yellow daisy flowers, this plant had very narrow, strongly quilled ocher-yellow flowers. Named after its discoverer, ‘Henry Eilers’ grows 4 to 5 feet tall, its upper stems bearing clusters of the smallish but long-lasting flowers. It makes an excellent fall cut flower, blooming in early September in Michigan. However, the large mature plants will generally require staking. A smaller three-foot version called ‘Little Henry’ was later introduced. Gardeners might find this shorter-statured variety a more practical size for the garden.

The common names of three-lobed coneflower, branched coneflower, or simply browneyed Susan are all descriptive. The plants grow 3 to 4 feet tall, with broad lower leaves and smaller upper leaves, often parted into three lobes. The small golden flowers are only 1 to 2 inches across, but are borne profusely in clusters at the ends of many thin branches. A mature plant will bear hundreds of flowers. A short-lived perennial, it is prone to self-sowing. This tendency can be used to advantage in naturalistic plantings and informal gardens, where precise location of each plant is less important than impact of color. The plant habit is quite upright and non-flopping, making these plants easy to accommodate in any garden.

Be aware that the heavy flower production may compromise the plant’s perennial nature. Cutting back the flower stems once they fade can encourage the plant to produce a basal rosette of foliage in the fall that will overwinter successfully. If allowed to flower uninterrupted, R. triloba will easily bloom from late July through most of October. Be on the lookout for seedlings in the spring and position them where you would like to see a bold display of color in two years’ time.

In the early 2000s, a significant color variation, now named ‘Prairie Glow,’ was discovered in an Iowa field. The flowers range in color from burgundy to russet to orange, all of which are variously tipped in gold or yellow, looking like miniature versions of the colorful flowers on the R. hirta hybrids. Since ‘Prairie Glow’ is grown from seed, each plant will be slightly different, with varying color patterns. Buying green plants prior to bloom is a bit like choosing from a grab bag—great fun for gardeners who like surprises!

Rudbeckia species, varieties and cultivars are often lumped together in garden references, with generalized advice and descriptions like “easy for beginners,” “long blooming,” and “low-maintenance perennials.” While it is true that some generalizations about appearance and culture can be made (rudbeckias usually have yellow, daisy-like flowers; rudbeckias prefer full sun), broad statements like these don’t do justice to the diversity of the genus, nor do they educate the gardener about the finer details of growing them.

A common misconception is that rudbeckias are drought-resistant. Anyone who has seen a planting of R. fulgida ‘Goldsturm’ in the middle of a drought would disagree.

Rudbeckias, with the exception of the R. hirta hybrids, are late-summer and early-fall bloomers. Their yellow and gold color palette suits the season well, making rudbeckia a perfect bridge between summer and autumn. To create harmonious combinations, it is worthwhile to make a distinction between the golden-hued rudbeckias and the true yellow ones.

Bright gold can be harsh when juxtaposed with pink or rose-toned flowers, but can be used to great effect when contrasted with blue or purple. Gold-toned rudbeckias like perennial black-eyed Susan (R. fulgida) and brown-eyed Susan (R. triloba) pair perfectly with the tan and taupe colors of ornamental grasses. Golden rudbeckias also look great with burgundy-foliage sedums or those with coral-toned flowers, like ‘Autumn Joy’ sedum.

The true yellow-colored rudbeckia ‘Herbstsonne’ would be smashing with red cardinal flowers (Lobelia), hibiscus, and a dark-leafed cimicifuga (Actaea) like ‘Hillside Black Beauty’—if you have a garden large enough to accommodate them all! Great coneflower (Rudbeckia maxima) is at home with other bottomland native plants such as turtlehead, great blue lobelia (Lobelia siphilitica), and any of the tall ironweeds.

Pair any rudbeckia, regardless of flower color, with Russian sage, agastache, Joe pye weed, and late-blooming lilies and daylilies that share the late-summer bloom period. Rudbeckias also provide a late-season nectar source in butterfly gardens. Plant them with other butterfly favorites like allium, butterfly bush, coneflower (Echinacea), blazing star (Liatris), Culver’s root (Veronicastrum), goldenrod, and veronica.

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‘Prairie Glow’

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It droops and wilts badly. We also know that cutleaf coneflower (R. laciniata) and sweet coneflower (R. subtomentosa) are found in nature in moist sites—the gardener should not be deceived into planting them, or their cultivars, in sandy, dry soils.

The species R. hirta (black-eyed Susan) and R. triloba (brown-eyed Susan) are more drought tolerant, but even they may develop powdery mildew if allowed to dry out too many times. I made the mistake of planting the great coneflower (R. maxima) in dry, sandy soil, only to discover that its native habitat is river bottomland. Only when I planted it in wetter soil did it develop the big, rounded leaves and dramatic flower stems for which it is known. It is worthwhile to do a bit of research about the specific rudbeckias you have chosen. If the perennial in question is a native plant or a hybrid of a native, consult a book or website about natives to learn about its natural habitat. Let Mother Nature guide you.

The story about the demise of the classic variety ‘Goldsturm’ also contradicts the old saw that all rudbeckias are low-maintenance perennials. It takes a lot of work to keep a disease-prone plant healthy and attractive. I am loath to malign a variety with such a long history of outstanding performance, but it has been superseded, as was necessary, with the advent of the debilitating disease trio mentioned earlier. It is now easy to find good substitutes with a similar look but far fewer disease and maintenance problems. Additionally, the other rudbeckia species described in this article are not susceptible to the same fungi that plague ‘Goldsturm.’

Most but not all of the rudbeckias mentioned produce fertile seed, and the issue of self-sowing must be considered by each gardener. Native rudbeckias are typically more fertile than hybrid cultivars, but be aware that even hybrids can produce fertile seeds. Deadheading can help reduce self-sowing, but will deprive songbirds of a favored food source.

Proven Winners (2)

Limelight Prime hydrangea shares the same qualities of the classic ‘Limelight’ hydrangea, while adding several attributes. It has a denser, more compact habit that creates a lush, full look. This smaller size can be a better fit for many home landscapes and gardens. Strong, sturdy stems won’t flop over, even under the weight of very large blooms. Limelight Prime blooms earlier and has better flower color, from its early summer lime green phase all the way through to pink and red tones in the fall.

Height: 4-6 feet. Width: 4-5 feet. Light: Full sun to part sun. Zone: 3.

Electric Love has a straightforward claim to fame: it is the first red-flowered, dark-leaved weigela on the market. Vibrant red flowers are contrasted against nearly black foliage for a striking look. Because of its compact size, Electric Love is useful along a walkway, or it can be planted in the front of mixed garden beds.

Height: 1-2 feet. Width: 2-3 feet. Light: Full sun. Zone: 4.

Star Roses & Plants

Petite Knock Out is the first-ever miniature Knock Out rose. It has the same easy care as the other roses in the popular family, but in a very compact size. Not only is the overall plant petite, but the fire engine red blooms are commensurately sized and dainty at roughly 1-1/2 inches in diameter. Plant this rose in containers on your porch or patio, or in mass for a low patch of bold red color.

Height: 18 inches. Width: 18 inches. Light: Full sun. Zone: 4.

Plants Nouveau

‘Haas’ Halo’ (Hydrangea arborescens) boasts sturdy stems, deep bluish-green, glossy foliage, and huge, white, lacecap flowers. In fact, each bloom is up to 14 inches in diameter. As a bonus, they make lovely dried flowers. While it would enjoy moist soils, ‘Haas’ Halo’ can also handle droughts and a summer full of heat and humidity. It is beautiful planted as a specimen and just as pretty in groups along a woodland edge.

Height: 3-5 feet. Width: 3-5 feet. Light: Full sun to part shade. Zone: 3.

Virginia sweetspire (Itea virginica) is a solid performer for many reasons: lovely fragrant flowers, adaptability to both wet soils and shade, and striking shades of red and purple foliage in the fall. Scentlandia improves on the classic species. First, it grows in a more compact and refined habit. Next, better hardiness—important since Virginia sweetspire blooms on old wood. Improved hardiness assures that, even in the colder parts of its hardiness zone, flowering (and thus fragrance) will be reliable. Speaking of fragrance, Scentlandia perfumes the air with notably fragrant flowers.

Height: 2-3 feet. Width: 2-3 feet. Light: Sun to shade. Zone: 5.