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Black-Eyed Susans

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Picture of Rudbeckia flower.

Picture of Rudbeckia flower.

David Beaulieu

Plant Taxonomy of Black-Eyed Susans:

Plant taxonomy classifies black-eyed susans as Rudbeckia hirta.

Plant Type:

Rudbeckia hirta flowers can be either annuals, biennials or short-lived herbaceous perennials, depending upon variety and growing conditions.

These distinctions are sometimes lost on the casual observer, since the plants re-seed readily: if you see the seedlings sprouting up in the same place year after year, you could easily gain the impression that you have a perennial (even if you do not, in fact, have a perennial type).

Characteristics:

Black-eyed susans are valued as long-blooming perennials, putting out numerous flowers non-stop for most of the summer and into early autumn. The cheerful flowers consist of golden petals that radiate from a dark cone (thus the common name, even though the color is more of a dark brown). Small hairs cover the stems and leaves, accounting for the specific epithet, hirta (Latin for "hairy"; think "hirsute"). When in bloom, black-eyed susans stand 2-3 feet tall, with a spread of up to 2 feet.

Planting Zones for Black-Eyed Susans:

This member of the aster family can be grown in planting zones 4-9. Indigenous to North America, they are native to or have become naturalized in wide swaths of territory across the U.S.

Sun and Soil Requirements for Black-Eyed Susans:

Plant in full sun (or partial sun in the South) and in an average, well-drained soil. These cheerful plants are drought-tolerant perennials once established but perform better if watered during dry spells. I grow my own in a nook of my garden that I hardly ever water. I get blooms every year and sufficient color to satisfy me in this area, although the display would be enhanced if I bothered to irrigate during hot, dry spells in the summer.

Uses for Black-Eyed Susans in Landscaping:

Black-eyed susans are often massed together in perennial borders and are effective at erosion control. Like 'Becky' shasta daisies, they also make fine cut flowers. Popular in wildflower gardens, this is one type of wildflower that almost everyone knows, even non-plant lovers.

Care for Black-Eyed Susans:

Black-eyed susans are susceptible to powdery mildew. To prevent an infestation, keep your Rudbeckia flowers thinned out. If the powdery mildew is already present, treat with a fungicide. Black-eyed susan flowers can also profit from deadheading. To propagate and/or rejuvenate, divide in spring.

Outstanding Characteristic:

It's difficult to say if the best feature of these plants is the abundance of their flowers or the fact that they bloom for such a long time. But I do find the latter quality especially appealing: plant black-eyed susans in a corner of your garden, and for half of the growing season you're sure to have color there.

Wildlife Attracted to Black-Eyed Susans:

Black-eyed susans are plants that attract butterflies, as well as birds.

Other Types of Rudbeckia Flowers, Confusing Common Names:

There are many types of Rudbeckia flowers, another popular species being fulgida. Many grow the cultivar, 'Goldsturm' (Rudbeckia fulgida var. sullivantii 'Goldsturm').

Rudbeckia flowers are sometimes referred to as "coneflowers," but that common name is more typically applied to Echinacea, which includes the coneflowers such as the old standby, purple coneflower (Echinacea purpurea) and newer types such as the orange coneflower that I grow. While related, plants in the Echinacea genus are a distinct group from those in the Rudbeckia genus. Such common names can be confusing, which is why we use scientific plant names when specificity is paramount.

Another common name that can create some confusion is "Gloriosa daisy." Sometimes used synonymously with "black-eyed susan," I prefer to restrict its usage to references to Rudbeckia hirta 'Gloriosa.' The latter bears bi-colored flowers ("tri-colored" flowers if you count the central cone):

  1. A dark cone stands at the center.
  2. A rust-colored ring surrounds this cone, at the base of the petals.
  3. The remaining 2/3 of each petal is golden

For a picture of Gloriosa daisy, click on the photo above to access the mini-photo gallery.

Related Video
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