BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Rudbeckia hirta | Black-Eyed Susan 



GENERAL BOTANICAL CHARACTERISTICS : 
Black-eyed Susan is a native, warm-season, annual, biennial or
short-lived perennial forb [26,34].  It has one to a few stems [4] 12 to
40 inches (0.3-1.0 m) tall [26], which are erect and sometimes sparingly
branched [33].  The lower leaves are 2 to 6 inches (5-15 cm) long [28],
alternate and petioled [34].  The upper leaves are mostly sessile [26].
The inflorescences are few to many flower heads on peduncles 2 to 8
inches (5-20 cm) long [34].  The fruit is an achene 0.06 inches (1.5 mm)
long; there is no pappus [33].  Black-eyed Susan has a taproot or a
cluster of fibrous roots [28].  It is a mycorrhizal species [43].


RAUNKIAER LIFE FORM : 
   Hemicryptophyte


REGENERATION PROCESSES : 
Black-eyed Susan reproduces sexually by seed [4,28].  It is pollinated
by bees and flies [15,22].  It also reproduces vegetatively [56] by
sprouting from the root crown [48].

In remnant tallgrass prairie in central Illinois, black-eyed Susan seeds
made up 2.4 percent of germinable seeds found in the seedbank.  Fifty
percent of black-eyed Susan seeds were in the upper 0.8 inches (2 cm) of
soil; the rest were in the next 3 inches (8 cm) of soil.  The seeds
occurred in high-density clumps rather than being randomly dispersed.
Black-eyed Susan was a very minor component of the vegetational cover.
There were more black-eyed Susan seeds in the seedbank than would be
predicted by its importance value [38].

Black-eyed Susan seed germination varies with area and time of
collection, and with germination conditions.

Black-eyed Susan seeds were collected from wild seed sources in central
Wisconsin in the fall of 1976.  The seeds were given cold, dry
stratification for at least 2 months, before germination testing.
Germination ranges were 0 to 38 percent.  When grown in soil in 1977,
none germinated; in 1978, germination in soil ranged from 10 to 24
percent.  The higher rate in 1978 was probably due to reduction in
dormancy and to higher germination temperatures than in 1977.  Light had
no marked effect on the germination of black-eyed Susan seeds in this
study.  Wild black-eyed Susan had a very wide range of Pure Live Seed
values [31].

In a germination study of Wisconsin tallgrass prairie plants, seeds were
collected from the southern tier of Wisconsin counties.  With 3 months
cold stratification, black-eyed Susan had a maximum of 46 percent
germination.  However, germination values for seeds collected in
different years fluctuated greatly.  In some years seeds would germinate
even though unstratified [29].

In trembling aspen (Populus tremuloides)-dominated vegetation in western
Colorado, black-eyed Susan seeds were collected September 2-3, 1981.
Germination tests were conducted within 6 months of collection.
Germination rates were very low in the absence of light and without
stratification.  Germination rates ranged from 24 to 36 percent for
moistened seeds grown in light and stratified 30 to 120 days [36].


SITE CHARACTERISTICS : 
Black-eyed Susan is found on clayey loam to sandy loam soils.  It has
low to moderate water requirements, and grows in full sun to partial
shade [51].  It is found in plains and open woods [18,19], sunny
roadsides and meadows [57], sandhills and bogs [12], and disturbed
places [35].

Black-eyed Susan occurs at the following elevations:

                   Elevation (feet)     Elevation (meters)

        CA            328-3,937           100-1,200  [34]
        CO          5,000-9,500         1,524-2,896  [17,33]
        WY              8,200               2,500    [17].               


SUCCESSIONAL STATUS : 
Facultative Seral Species

Black-eyed Susan is considered a pioneer species [31], and can be
dominant in early stages of succession [50].

Black-eyed Susan is part of the weed stage of abandoned fields in
central Oklahoma and southeastern Kansas [59].

At the establishment of the Curtis Prairie in south-central Wisconsin
between 1936 and 1941, black-eyed Susan plants were left intact, as they
already occurred in some fields.  They persisted a short time, spreading
opportunistically into other areas.  Areas originally dominated by
black-eyed Susan were invaded extensively by various more aggressive
species [52].

In a tallgrass prairie establishment effort in southern Wisconsin, begun
in 1974, black-eyed Susan appeared in 1975, though it had not been
seeded.  It was abundant in the surrounding area, however [60].


SEASONAL DEVELOPMENT : 
Black-eyed Susan is able to flower its first year [28], but flowers more
prolifically its second year.  By the end of the first year it may begin
vegetative reproduction, and show a distinct "bunching" effect with 2 or
more shoots [46].  Topgrowth dies back each year [36,42].  Biennial and
perennial forms sprout the next spring from the root crown [48].
Black-eyed Susan initiates growth in late spring and becomes dormant by
early fall [2].

Black-eyed Susan flowering times are:

                  Begin          Peak           End
                Flowering      Flowering     Flowering

     FL         May            ----          October   [12]
     IL         June           ----          September [44]
     KS         June           ----          August    [4]
     MI         June           ----          August    [22]
     MN         June           July          July      [15]
     MO         June           ----          August    [37]
     NC         May            ----          July      [48]
     ND         July           July          August    [11]
     SC         May            ----          July      [48]
     TX         June           ----          ----      [20]
     WI         June           ----          August    [16]
 Great Plains   May            ----          September [28]
 Northeast US   June           ----          October   [26].

Related categories for Species: Rudbeckia hirta | Black-Eyed Susan