Plant Taxonomy of Black-Eyed Susans:
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).
Black-eyed susans are valued as long-blooming plants, 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 species name, 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
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.
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
Outstanding Characteristic of Black-Eyed Susans:
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:
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." Note, however, that although the purple coneflower (Echinacea purpurea) is related, it is not a Rudbeckia. Such common names can be confusing, which is why we use scientific names for plants.
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 tri-colored flowers:
- A dark cone stands at the center.
- A rust-colored ring surrounds this cone, at the base of the petals.
- 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.