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The gardener’s guide to rudbeckia

Rudbeckia

One in an occasional series of guides on growing popular plants. Other guides include azalea, redbud, Lenten rose, peony, elephant ear, coleus, lantana, coneflower and savory calamint.

A common name for rudbeckia is coneflower, not to be confused with purple coneflower. Its most culturally resonant member is the biennial wildflower known as the black-eyed Susan, but we will focus on the longer lived hardy perennials that are well suited to garden use. As with the calamint, rudbeckia is valued for its long season of flowering at the hottest time of year.

(iStock)

The best known of these is the Rudbeckia fulgida and the selection known as Goldsturm, with each plant presenting loads of big yellow daisies from July onward.

Size

Goldsturm and other fulgida varieties grow to about 30 inches high and 24 inches wide. In rich soils and in time, clumps spread wider and may need narrowing. Other rudbeckias discussed below grow to eight feet or more.

Use and Placement

Just a few clumps can spread to 10 or 12 feet, so they should be planted in spacious borders and beds. They are effective in combination with fine textured ornamental grasses such as pennisetum, calamagrostis and panicum.

Planting and Care

Rudbeckia fulgida will endure average dry soils, but it is more vigorous and robust in fertile, humusy soil that retains moisture but is well drained. Plants will take partial shade but need a site with good air circulation. This is because a fungal leaf spot disease named septoria can become established and quickly mar the foliage. Preventive fungicide sprays are effective, but the better remedy is to plant rudbeckia in open, breezy locations and to make sure that all fallen leaves and stalks are removed at the end of the growing season.

Varieties

Other varieties of R. fulgida besides Goldsturm include Goldschirm, Pot of Gold and Viette’s Little Suzy. The last grows to just 15 inches and is useful in small gardens.

An alternative garden-worthy species is Rudbeckia triloba, named for its three-lobed leaves. Its flowers are smaller but profuse and handsomely clustered. Triloba is short-lived but seeds prodigiously, allowing a colony to sustain itself. Unwanted seedlings can be removed in spring, but avoid planting with other coneflowers to avoid confusion. The triloba will take over.

Rudbeckia triloba. (Mt. Cuba Center)
Rudbeckia subtomentosa Henry Eilers. (Mt. Cuba Center)
Rudbeckia maxima. (Mt. Cuba Center)
Rudbeckia Goldsturm. (iStock)
TOP LEFT: Rudbeckia triloba. (Mt. Cuba Center) TOP RIGHT: Rudbeckia subtomentosa Henry Eilers. (Mt. Cuba Center) BOTTOM LEFT: Rudbeckia maxima. (Mt. Cuba Center) BOTTOM RIGHT: Rudbeckia Goldsturm. (iStock)

The flower of the giant coneflower, Rudbeckia maxima, consists of drooping yellow petals around a purple-brown cone — a clear echo of the blooms of other rudbeckias. But the similarity ends there. The giant coneflower is marked by large blue-green oval leaves that yield to a wiry, branched stalk bearing the blooms as high as eight feet or more. Although each plant is relatively narrow, it shouldn’t need staking. It does prefer more moisture than its lower brethren and as a garden plant, it should be planted in groups to rise up and over neighboring perennials and shrubs. A single plant would look awkward and lonely.

A much underused coneflower is Rudbeckia subtomentosa, best represented by a variety named Henry Eilers. Its blooms have a pinwheel effect because each of the petals is rolled into a tube. This is another imposing member of the clan, growing to six feet, and blooming for weeks in midsummer. It needs soil that retains moisture but is not wet.

The cutleaf coneflower, Rudbeckia laciniata, is another large, garden worthy species, especially the cultivar Herbstsonne (Autumn Sun), which blooms from the end of July well into October. It is a valuable part of the perennial and ornamental grass border planted to take the garden from late summer into fall.

Lead illustration by Washington Post Staff/iStock/Mt. Cuba Center. Icon illustrations by Jeannie Phan.

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