blackeyed susan (Rudbeckia hirta)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

COMMON NAMES:
black-eyed susan
gloriosa daisy
yellow daisy
blackeyed susan

 

SCIENTIFIC SYNONYMS:
Centrocarpha gracilis D.Don ex Sweet
Centrocarpha hirta D.Don ex Sweet
Coreopsis hirta Raf.
Rudbeckia serotina Nutt.

 

CONFIRMATION STATUS: Pending confirmation.

 

TAXONOMY: The currently accepted scientific name of blackeyed
susan is Rudbeckia hirta L. Rudbeckia hirta was first described by
Linnaeus in 1753 in Species Plantarum.  In 1904, O.A. Farwell described
the variety pulcherrima in the Annual Report of the Michigan Academy
of Science.  Then, in 1957, R. Perdue, Jr., published "Synopsis of Rud-

beckia Subgenus Rudbeckia" in which the four recognized varieties
included hirta, pulcherrima, angustifolia and floridana. These four
varieties are still recognized by most botanists. The Atlas of Virginia
Flora does not designate which of the two varieties of Rudbeckia hirta
occurs in Facquier County; for the Nature Guide variety pulcherrima
will be used.

 

NATIVE STATUS: Native, United States and Canada.

 

GENERAL BOTANICAL CHARACTERISTICS:

 

Habit: This is a native biennial or short-lived perennial plant that is about

1-2½' tall. Blackeyed susan has a complex life cycle - being at times an-

nuals, biennials and perennials. Varieties angustifolia and floridana are

known to undergo all three life cycles. Variety hirta is biennial or peren-

nial, and variety pulcherrima is annual or perennial. It occasionally branch-

es near the base, with each stem producing a single composite flower. The

stems have long white hairs.

 

Leaves: The alternate leaves are greyish green and covered with small stiff
hairs, providing them with a rough texture. The leaves are up to 7" long and
2" across, and lanceolate, oblanceolate, or ovate. Their margins are ciliate
and rather smooth, with or without a few blunt teeth. The basal leaves have
long hairy petioles, while the middle and upper leaves have short petioles
or clasp the stem.

 

Flowers: The upper stems are long and devoid of leaves, each producing

a single composite flower. This flower consists of many dark brown disk

florets, forming a flattened cone, surrounded by 8-20 ray florets that are

bright yellow (rarely with patches of maroon near the base). The style-tips

of the disk florets are slender and pointed. Each composite flower is about

2-3" across, and has no noticeable scent. Blackeyed susan blooms primari-

ly from early to mid-summer for about a month, although some plants will

bloom during the late summer or fall.

 

Fruit/Seeds: The achenes are black, oblong, finely nerved, and without

tufts of hair.

 

Roots: The root system consists of a central taproot and is without

rhizomes this plant reproduces entirely by seed.

 

REGENERATION PROCESS: Blackeyed susan propogates itself
by reseeding.

 

HABITAT TYPES: In native habitats, blackeyed susan occurs in mesic
to dry prairies, mesic to dry upland forests, particularly in open rocky
areas, as well as savannas and limestone glades. In developed areas, it
can be found in pastures and abandoned fields, areas along railroads and
roadsides, on eroded clay slopes, and miscellaneous waste areas. Black-
eyed susan colonizes disturbed areas readily, and recovers moderately
well from fires.

 

SITE CHARACTERISTICS: Black-eyed susan is naturalized in most
of the states east of Kansas and the bordering areas of Canada. It is adapt-

ed throughout the Northeast on soils with a drainage classification range

from well drained to somewhat poorly drained. It will perform acceptably

on droughty soils during years with average or above rainfall, but best

growth is achieved on sandy, well drained sites. It is winter hardy in areas

where low temperatures are between -30 ° and -20 °F.

 

SEASONAL DEVELOPMENT: Varieties floridana, hirta and
pulcherrima can be found in bloom from spring to fall, but variety
angustifolia has a shorter flowering period lasting from spring to
summer. Studies show that several factors including climate warm-

ing and day length can induce or delay the flowering cycle. Increas-

ing temperature seems to be correlated with an earlier onset of

blooming. If day length never increased in the spring, blackeyed

susan would never grow beyond its rosette, therefore never produc-

ing flowers.

 

GENERAL DISTRIBUTION: Blackeyed susan spans the entire U.S.,
except Arizona and Montana, and the southern reaches of Canada. Var-

iety pulcherrima can be found throughout this entire range, but the other

varietal populations are localized.  Variety floridana is isolated in south-

ern Florida, while variety angustifolia grows through the entire Gulf coast-

al plain.  Variety hirta is mostly found from the Appalachians to Illinois,

but it can be found along the entire U.S. Atlantic coast.

 

SKY MEADOWS DISTRIBUTION: To be determined.

 

IMPORTANCE AND USES: The composite flowers appeal to a wide
range of insects, particularly bees and flies, as well as some wasps, but-

terflies, and beetles. The bees collect pollen or suck nectar, and include

little carpenter bees, leaf-cutting bees, green metallic and other halictine

bees, andrenid bees, and others. Some andrenid bees, such as Andrena

rudbeckiae and Heterosarus rudbeckiae, prefer visiting the flowers of

black-eyed susan and closely related plants. Among the flies that visit

the flowers, syrphid flies, bee flies, and tachinid flies are well represent-

ed. The caterpillars of Chlosyne nycteis (silvery checkerspot) feed on the

leaves. Many mammalian herbivores are not particularly fond of the

coarse leaves – they have low food value, and there have been occasional

reports of this plant poisoning cattle and pigs. The seeds are eaten occa-

sionally by goldfinches.

 

Cultivars of Rudbeckia hirta have been hybridized with cultivars of
Laciniata, and many of the types commonly used in cultivation are,
in fact, hybrids. 'Kelvedon star', 'Gloriosa' and 'Irish eyes' are a few of
the more popular cultivars. Unfortunately, Rudbeckia hirta is especially
susceptible to powdery mildew. Black-eyed susan is an excellent choice
for prairie restorations, or the first-year planting of a wildflower garden,
as it may bloom during the first year from seed. Sometimes, this plant
will reseed itself with such abandon it can become aggressive, but it will
lose ground to the longer-lived perennial plants as they mature. Black-
eyed susan can be distinguished from other Rudbeckia spp. by its lance-

olate hairy leaves and the long hairs on the stems; most of the leaves

occur toward the base of each stem, and never have lobes. The species

Rudbeckia fulgida (orange coneflower) is quite similar in appearance, but

usually blooms later, and has style-tips that are shorter and more rounded.

 

 

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