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1
HortTechnology 11(1):26-30, January-March 2001
A Publication of the Amercian Society for Horticultural Science, Alexandria, VA 22314
Research Reports
Growth, Flowering, and Survival of Black-eyed Susan
from Different Regional Seed Sources
Jeffrey G. Norcini, Mack Thetford, Kimberly A. Klock-Moore, Michelle L. Bell,
Brent K. Harbaugh, and James H. Aldrich
A
DDITIONAL INDEX WORDS
. ecotypes, Rudbeckia hirta, wildflowers
S
UMMARY
. Growth, flowering, and survival of black-eyed susan (Rudbeckia hirta L.) from three seed
sources—northern Florida (NFL), central Florida (CFL), and Texas (TEX)—were evaluated under low
input conditions for one growing season at four sites in Florida. Two sites were in AHS Heat Zone 9
while the other two were in AHS Heat Zones 10 and 11. Growth, onset date of flowering, and number of
flowers at peak flowering varied by site. With few exceptions, plants tended to reach peak flowering at
about the same time. Flower diameter varied by seed source with TEX>NFL>CFL. While TEX plants
were perceived as the showiest, NFL and CFL plants persisted longer under the low input conditions in
Florida, and hence provided some evidence of adaptation to regional site conditions.
_________________
Florida Agricultural Expt. Station Journal Series No. R-07412. We thank Dr. Frank G. Martin for
assistance with the statistical analysis.
2
Black-eyed susan, Rudbeckia hirta, is a wildflower native to much of the United States
(Rickett, 1967), including Florida (Wunderlin, 1998). It is thought that through a process of natural
selection, populations of native wildflowers may perform better in one location (environment) than
another. The selection process involves not only climate but also soils, insects, and microorganisms - the
ecotype concept (Turesson, 1922).
Few published studies have focused on the ecotype issue with respect to native wildflowers.
Although black-eyed susan is considered an obligate long-day plant (LD) (Garner and Allard, 1925),
Beckwith (1991) observed that a Texas ecotype had a weak facultative LD flowering response, while a
northern ecotype was an obligate LD plant. Celik (1996) also noted a difference in flowering among
black-eyed susan ecotypes. In a study conducted in north Florida (Norcini et al., 1998), a northern
Florida ecotype of black-eyed susan flowered until the end of the study (mid-October) whereas a Texas
selection senesced and/or succumbed to disease by mid-August. There were no differences in the level
of insect damage (which was minimal) and neither ecotype exhibited any signs of drought stress. A
naturally-occurring selection from central Florida also outperformed two black-eyed susan cultivars
('Sonora' and 'Indian Summer') in a formal bedding plant evaluation conducted in central Florida (Howe,
1998).
Latitudinal effects on population adaptation are thought to occur in as little as 402 to 563 km
(250 to 300 miles) (S. Meyer, personal communication). There are latitudinal ecotypes of black-eyed
susan, as noted above, as well as of goldenrod (Solidago sempervirens L.) (Goodwin, 1944). However,
other environmental conditions such as temperature, moisture, and mineral nutrition can affect species
adaptation. Murfet (1977) points out several examples in which these factors affected flowering of forbs
or grasses. In mountainous regions, populations of a species can be adapted to different elevations
because of differences in climate (Meyer and Paulsen, 2000). Gordon and Rice (1998) as well as Kindell
3
(1993) provided strong evidence of an environmental influence on growth and/or fecundity of wiregrass
(Aristida beyrichiana Trin. & Rupr.) populations. Although evidence of genetic differences (based on
isozyme analysis) was lacking, results of a reciprocal transplant study implied that genetic differences
exist among wiregrass (Gordon and Rice, 1998).
The objective of this study was to evaluate, under low input conditions, the effects of site (four
sites in Florida, representing AHS Heat Zones 9, 10, and 11) and seed source (northern Florida, central
Florida, and Texas) on growth, flowering, and survival of black-eyed susan. Based on the ecotype
concept, black-eyed susan should perform better under conditions from which the seed were derived
than when seed were used from a different environment. Differences in growth, flowering, or survival
due to site or seed source could affect recommendations for landscape use of black-eyed susan.
Materials and methods
P
LANT MATERIAL
. A northern Florida ecotype (NFL) of black-eyed susan originated from seed
collected during 1997 from native populations located primarily in the Red Hills region of the Florida
panhandle and extreme south Georgia (AHS Heat Zone 9; USDA Hardiness Zone 8b). All collection
sites were upland. Populations from which seed were collected were growing under a high canopy of
slash, loblolly, or longleaf pine (Pinus elliotii Engelm., Pinus palustris Mill., and Pinus taeda L.,
respectively) that may have been subjected to periodic prescribed burns. Leaves and stems of NFL are
dark green with short, coarse hairs. The flowers are about 3.8 to 5 cm (1.5 to 2 inches) in diameter; ray
flower color is yellow-orange (Royal Horticulture Society [RHS] 12A) (Royal Horticulture Society
Colour Chart, 1991). Overall plant height in bloom is 0.46 to 0.61 m (1.5 to 2 ft) (Norcini et al., 1999).
A central Florida seed source (CFL) was a selection that originated from two plants purchased
from Viola Wildflower of Sarasota, Florida. It is a variant of black-eyed susan that has yellow ray
flowers (RHS 6A) and was named ‘Viola’s Lemonade’ by the grower. This selection originated from a
4
chance seedling collected by the grower in a mesic area of eastern Sarasota County in central Florida
(AHS Heat Zone 10; USDA Hardiness Zone 9a). In addition to a different flower color, CFL appears to
be slightly smaller overall, including flower size, compared to the NFL. Leaf and growth characteristics
are similar.
The third seed source was a selection of a Texas ecotype (TEX) that was produced by Wildseed
Farms, Fredericksburg, Texas (AHS Heat Zone 9; USDA Hardiness Zone 8a). This selection is much
larger than either NFL or CFL, with flowers, foliage, and overall size appearing to be 150 to 200%
greater than that of NFL (Norcini et al., 1998). Its foliage has lighter green leaves with longer, soft hairs
compared to NFL and CFL. Ray flowers are two shades of yellow-orange—RHS 17B on the basal part
of the petal and RHS 14A on the outer portion.
S
ITES
. Plantings were established at four sites that represented AHS Heat Zones 9, 10, and 11
(average number of days > 30
o
C [86
o
F] is 120 to 150, 150 to 180, and 180 to 210, respectively). The
sites were at four University of Florida/Institute of Food and Agricultural Sciences Research and
Education Centers (RECs)—West Florida REC, Jay (31.0
o
N, 87.2
o
W; AHS Heat Zone 9; USDA
Hardiness Zone 8b), North Florida REC, Monticello (30.5
o
N, 83.9
o
W; AHS Heat Zone 9; USDA
Hardiness Zone 8b), Gulf Coast REC, Bradenton (27.4
o
N, 82.5
o
W; AHS Heat Zone 10; USDA
Hardiness Zone 9b), and Ft. Lauderdale REC (26.1
o
N, 80.2
o
W; AHS Heat Zone 11; USDA Hardiness
Zone 10a). The sites at Jay and Monticello were less than 56 km (35 miles) apart in latitude (based on a
conversion factor of 111 km [69 miles] per degree latitude) but were over 483 km (300 miles) north of
Ft. Lauderdale and over 322 km (200 miles) north of Bradenton. Soil at all sites was sandy and of low
fertility (Table 1), and contained several nematode genera (Table 2).
C
ULTURE
. During the first week of Jan. 1998, seeds were sown in Metro-Mix 220 (Scotts Co.,
Marysville, Ohio) in cell packs. Seedlings were fertilized once per week after the first true leaves appeared
5
with N at 50 mg
•
L
-1
(ppm) (15N-13.2P-12.4K; Peters 15-30-15, Scotts Co., Marysville, Ohio), and once
with trace elements (DynaGreen at 530 mg
•
L
-1
(ppm); A.H. Hummert, St. Louis, Mo.).
Seedlings were transplanted during the first week of March 1998 to a 3.1 X 3.7-m (10 X 12-ft)
plot, with plants spaced 0.61 m (2 ft) on center. All sites were previously in turfgrass, had not been
recently cultivated, and were in full sun. Turfgrass was killed with a nonselective herbicide (glyphosate)
2 to 4 weeks before planting. At Bradenton, Ft. Lauderdale, and Jay all turfgrass was removed, and then
plots were rototilled and raked before planting. However at Monticello, dead turfgrass remained in the
rows and between plants, with a 20.3 - 22.9 cm (8 to 9 inches) ring of turfgrass-free soil maintained on
all sides of each plant. The entire 3.1 X 3.7-m plot at all sites was mulched with 5 to 7.6 cm (2 to 4
inches) of pine straw or shredded cypress bark (Ft. Lauderdale only). Weeds that emerged were
manually removed.
Plants were irrigated for 2 to 4 weeks after transplanting to aid in establishment. From mid-April
through mid-June, most of Florida experienced a drought that was exacerbated by unseasonably warm
weather in May and June (mean [± SE] departures from normal maximum temperature averaged over
sites: May - +2.7 ± 1.2
o
C [+5.1 ± 2.3
o
F], June - +3.6 ± 1.0
o
C [+6.5 ± 1.8
o
F]), so periodic
supplemental irrigation was necessary at one or more sites. No supplemental fertilizer was applied.
Pesticides were not used except for fire ant control, and for a major aphid infestation at Ft. Lauderdale
(no apparent preference for TEX, CFL, or NFL was observed) when imidacloprid (Marathon 1G;
Olympic Hort. Products, Mainland, Pa.) (1.3 g [0.5 oz]) at base of plant and watered in) was applied to
all plants.
P
ARAMETERS
. Total plant height (measured from the soil surface to the top of the plant) and two
widths (width at widest point, and width perpendicular to widest point) were recorded at transplanting,
and approximately every 30 days; all measurements included the contribution of inflorescences. A plant
6
growth index (GI) was calculated as follows: GI = (height + average width)/2, where average width was
the average of width at the widest point and width perpendicular to the widest point. For each plant, date
of first fully opened flower, number of fully opened flowers (once per week initiated at first flowering),
and diameter of three individual fully opened flowers were recorded. Percent survival was also
monitored monthly.
EXPERIMENTAL DESIGN AND ANALYSIS. The experimental design was a 4 (site) by 3 (seed
source) factorial arranged in a completely random design, with 10 single plant replications per seed
source per site. Due to a technical problem at Ft. Lauderdale, there were 3, 3, and 11 single plant
replications for NFL, CFL, and TEX, respectively. Data (except survival data) were subjected to
analysis of variance using the General Linear Model (GLM) procedures of SAS. Main effects means
(Site, Seed source) were separated using Tukey’s Studentized Range (
HSD
; α = 0.05). Significant
differences between two specific seed sources within or between sites were determined by the
LSMEANS/PDIFF option within the GLM procedure of SAS.
Results and discussion
G
ROWTH
. Increases in width and GI were significantly affected by site (Table 3). Plants tended
to grow more in the northern half of Florida (Monticello and Jay) than in southern half of Florida
(Bradenton and Ft. Lauderdale). TEX plants were perceived as larger than NFL or CFL because TEX
had 1) visibly larger leaves (data not shown) than either NFL or CFL, 2) the largest flowers
(F
LOWERING
, see below), and 3) flowers that were held only slightly above the vegetative growth in
contrast to NFL and CFL flowers which were held visibly higher above the mass of vegetative growth.
F
LOWERING
. Site affected date of first flowering in a manner analogous to the effect of site on
growth. Plants in the northern half of Florida (Jay and Monticello) generally started flowering about 1 to
2 weeks earlier than those in the southern half of Florida (Bradenton and Ft. Lauderdale) (Table 3). TEX
7
plants tended to start flowering later than either NFL or CFL, although seed source was not a significant
main effect at the 5% level for date of first flower (P = 0.092). However, peak flowering of TEX was
about 2 and 6 weeks earlier than CFL at Monticello and Ft. Lauderdale, respectively (Table 4). Peak
flowering dates of TEX and NFL at Monticello or Ft. Lauderdale were not significantly different (within
a site). There were no seed source differences in peak flowering date at Bradenton or Jay, nor were there
any trends in range of dates at which plants from different seed sources attained peak flowering.
The number of flowers at peak flowering was affected by site. Significantly (P = 0.05) more
flowers were produced on plants at Ft. Lauderdale, Jay, and Monticello compared to Bradenton but there
were no significant differences in number of flowers at peak among Ft. Lauderdale, Monticello, or Jay.
There was also a significant site by seed source interaction. However, within a site, the only significant
differences among seed sources were at Jay where TEX plants had substantially more flowers than
either CFL or NFL (Table 4). There were no trends in range of number of flowers at peak flowering.
Flower diameter was only affected by seed source (Table 3). TEX flowers (mean = 7.1 cm [2.8
inches] diameter) were 37% wider than NFL flowers (5.2 cm [2.0 inches] diameter) and twice as wide as
CFL flowers (3.6 cm [1.4 inches] diameter). The TEX and NFL results concur with the observations of
Norcini et al. (1998), while the average size of CFL concurs with the observations of Howe (1998). CFL
plants had the most consistent flower diameters (data not shown).
S
URVIVAL
. It was clear that NFL and CFL survived longer than TEX (Table 5) except at Jay.
None of the TEX plants at any site survived to November, and most of these plants were dead by the
beginning of September. This concurs with the findings of Norcini et al. (1998) who observed that most
TEX plants in north Florida were dead by mid-August. Furthermore, Norcini (unpublished observations)
has noted during the past few years that at least the top growth of TEX plants consistently dies in late
summer when plants are grown under low input conditions.
8
At Monticello, CFL survived better than NFL but there didn't seem to be any differences
between survival of CFL or NFL within other sites. Plants at Ft. Lauderdale were flooded for 3 days
(ankle-deep) in mid-September due to excessive rain. Because of the flooding, one of three NFL
survived and only three of 11 TEX survived. However, two of three CFL survived flooding, and while
flooded, new flowers even opened on CFL.
Conclusions
There are many factors that could have caused the plants to perform differently at the different
sites. Soil phosphorus level was very low at Bradenton (3.7 mg
•
kg
-1
[ppm]) compared to the other sites
(13 to 27 mg
•
kg
-1
[ppm] at the other sites). Researchers at Bradenton even observed purple foliage, a
sign of phosphorus deficiency.
Nematodes may have affected growth, flowering, and survival at Bradenton and Jay. Even
though black-eyed susan is unaffected by root-knot nematodes (Thetford and Kinloch, 1999), it could be
affected by other nematode species. Spiral nematode populations were very high at these sites compared
to other locations, especially at Jay, which had over two and a half times the number of spiral nematodes
compared to Bradenton (Table 2). This high spiral nematode level at Jay may have been the reason for
the relatively early death of CFL, NFL, and TEX compared to the other three sites. It does not seem
likely that root lesion nematodes caused a problem as McKeown et al. (1999) showed that black-eyed
susan was not infected by lesion nematodes (Pratylenchus penetrans [Cobb] Filipjev & Shuurmans
Stekhoven) after being exposed to it for 6 years in a prairie nursery; however, tolerance of black-eyed
susan to lesion nematodes (Pratylenchus spp. Filipjev) occurring in Florida has not been evaluated.
One factor that was not measured but could have had an effect on vigor and longevity was
disease. A preliminary pathological assessment indicated that TEX at Monticello succumbed to
9
Fusarium Synd. & Han. (J. Marois, personal communication). Work has begun to determine the relative
susceptibility of CFL, NFL, and TEX to Fusarium.
Photoperiod and temperature can have interactive effects on flowering of Rudbeckia (Murneek,
1940; Kochankov and Chailakhyan, 1986). The trend of plants from all three seed sources to start
flowering later at Bradenton and Ft. Lauderdale than at Jay and Monticello (Table 3) may have been due
to temperature (AHS Heat Zones 10 and 11 vs. 9). Since all three seed sources originated in the south,
plants may have had only a weak facultative LD response similar to what Beckwith (1991) noted about a
Texas ecotype of black-eyed susan. Hence, temperature may have had a greater effect on flowering
(Kochankov and Chailakhyan, 1986).
In conclusion, site had the greatest influence on growth and flowering of NFL, CFL, and TEX.
Those making recommendations or considering use of black-eye susan under low input conditions like
those in this study need to be aware of the variability that could occur at different sites despite apparent
similarities in environmental conditions and/or cultural practices. TEX plants were the showiest in
flower but plants from the two Florida seed sources were better able to survive the low fertility sites
under Florida conditions. This provides some evidence of adaptation to regional site conditions, and
hence, seed source should be considered when season-long persistence of black-eyed susan is an issue.
10
Literature Cited
Beckwith, D.D. 1991. Characterization of juvenility and photoperiodic responses of Rudbeckia
hirta originating from different latitudes. MS Thesis, Dept. of Horticulture, Va.
Polytech. Inst. and State Univ., Blacksburg.
Celik, M. 1996. Photoperiod and gibberellic acid effects on juvenility and flowering of
Rudbeckia hirta. MS Thesis, Dept. of Plant and Soil Sci., Miss. State Univ., Miss. State.
Garner, W.W. and H.A. Allard. 1925. Localization of the response in plants to relative length of
day and night. J. Agr. Res. 31:555-566.
Goodwin, R. H. 1944. The inheritance of flowering time in a short day species, Solidago
sempervirens L. Genet. 29:503-519.
Gordon, D.R. and K.J. Rice. 1998. Patterns of differentiation in wiregrass (Aristida beyrichiana):
Implications for restoration efforts. Restoration Ecol. 6:166-174.
Howe, T. 1998. Summary of flowering bedding plant trials spring 1998. Gulf Coast Res. Educ.
Ctr.-Bradenton Res. Rpt. BRA 1998-11. Univ. of Fla./Inst. of Food and Agr. Sci., Gulf
Coast Res. Educ. Ctr., Bradenton, Fla.
Kindell, C. 1993. Adaptive population differentiation in wiregrass in north Florida sandhills and
flatwoods. MS Thesis, Dept. of Biol. Sci., Florida State University, Tallahassee, Fla.
Kochankov, V.G. and M.Kh. Chailakhyan. 1986. Rudbeckia. In: CRC Handbook of Flowering,
Vol. V., A.H. Halvey (ed.), CRC Press, Boca Raton, Fla. pp. 295-320.
McKeown, A.W., J.W. Potter, M. Gartshore, and P. Carson. 1999. Long-term evaluation of
susceptibility of selected prairie species to the root lesion nematode Pratylenchus penetrans.
HortScience 34(3):521.
11
Meyer, S.E. and A. Paulsen. 2000. Chilling requirements for seed germination of 10 Utah species
of perennial wild buckwheat (Eriogonum Michx. [Polygonaceae]). Native Plants J. 1(1):18-
24.
Murfet, I.C. 1977. Environmental interaction and the genetics of flowering. Ann. Rev. Plant Physiol.
28:253-278.
Murneek, A.E. 1940. Length of day and temperature effects in Rudbeckia. Bot. Gaz. 102:269-
279.
Norcini, J.G., J.H. Aldrich, L.A. Halsey, and J.G. Lilly. 1998. Seed source affects performance
of six wildflower species. Proc. Fla. State Hort. Soc. 111:4-9.
Norcini, J.G, D.J. Zimet, C. Maura, S. Pfaff, and M.A. Gonter. 1999. Seed production of a
Florida ecotype of black-eyed susan. Fla. Agr. Expt. Sta. Circ. 1226.
Rickett, H.W. 1967. Wild flowers of the United States, Vol.2: The Southeastern states. McGraw-
Hill, New York, N.Y.
Royal Horticulture Society Colour Chart 1991. RHS Enterprises Limited, RHS Garden, Wisley,
Working, Surry, GU23 6QB England.
Short, D.E. 1994. Ground pearls in lawns. Univ. of Fla. Coop. Ext. Serv. Fact Sheet ENY-
322, 1 p.
Thetford, M. and R.A. Kinloch. 1999. Galling response of herbaceous and woody landscape
species grown in Meloidogyne incognita- and M. arenaria-infested soils. Res. Rpt. 1999-08,
Univ. of Fla./ Inst. of Food and Agr. Sci, W. Fla. Res. Educ. Ctr., Milton, Fla.
Turesson, G. 1922. The species and the variety as ecological units. Hereditas 3:110-113.
Wunderlin, R.P. 1998. Guide to the vascular plants of Florida. Univ. Press of Fla., Gainesville,
Fla.
12
Table 1. Soil characteristics (before transplanting) at the University of
Florida/Institute of Food and Agricultural Sciences Research Centers located at
Bradenton, Fort Lauderdale, Jay, and Monticello, Florida.
Soluble
salts NO
3
-N NH
4
-N P K
Site pH (mS•cm
-1
) (mg•kg
-1
) (mg•kg
-1
)
(mg•kg
-1)
(mg•kg
-1
)
Bradenton 5.01 0.08 1.00 2.70 3.70 3.7
Soil type: Eau Gallie fine sand (2 - 8% OM, 0 - 2 % slope) (Alfic haplaquod)
Ft. Lauderdale 6.74 0.30 9.00 5.00 27.00 3.7
Soil type: Margate fine sand (1.6% OM, nearly level)
Jay 5.85 0.12 1.00 3.30 20.50 41.7
Soil type: Orangeburg sandy loam (2.1% OM, 1% slope) (typic paleudult)
Monticello 5.66 0.10 5.50 2.00 13.00 7.4
Soil type: Fuquay fine sand (0.5 - 2% OM, 0 - 5% slope)
or Dothan loamy fine sand (<5% OM, 2 - 5% slope)
z
1.00 mg•kg
-1
= 1.00 ppm
13
Table 2. Nematodes and root insects present in the Florida evaluation sites before transplanting.
Nematodes and root insects Bradenton Ft. Lauderdale Jay Monticello
Lance (Hoplolaimus Daday) 0
z
0 0 7
Lesion (Pratylenchus Filipjev) 0 0 0 104
Ring (Criconemoides Taylor) 0 0 110 459
Root-knot (Meloidogyne Goeldi) 24 58 0 0
Sheathoid (Hemicycliophora 37 0 0 0
de Mann)
Spiral (Scutellonema Andrassy) 212 0 540 0
Sting (Belonolaimus Steiner) 3 0 0 0
Stubby root (Trichodorus Cobb) 0 10 0 0
Stunt (Tylenchorhynchus Cobb) 3 66 0 0
Ground pearls
y
(Margarodidae 0 0 N/A
x
56
Morrison)
z
No./100 cm
3
(100 cm
3
= 6.1 inches
3
) as conducted by University of Florida/Institute of Food
and Agricultural Sciences.
y
Ground pearls are scale insects that live in the soil and suck juices from roots; they are
generalist feeders (J. Rich, personal communication). Injury is most noticeable during periods of
plant stress (Short, 1994).
x
NA = Ground pearl analysis was not available for Jay.
14
Table 3. Effect of site and seed source on growth and flowering characteristics of black-eyed
susan.
Maximum increase in growth Date of first flower
(maximum minus initial) (days after transplant) Flower size
Ave.
Minimum/ Minimum/
Height
z
width
z
GI
z,y
maximum Diam maximum
Main effects (cm) (cm) (cm) Number values (cm) values
Site
x
Bradenton, Fla. 39.1 a 17.3 c 27.9 c 93.2 a 72 - 107 5.5 a 3.3 - 9.2
Ft. Lauderdale, Fla.
w
34.5 a 36.8 b 33.1 bc 87.7 ab 73 - 120 6.8 a 4.2 - 9.7
Jay, Fla. 47.1 a 28.6 b 38.2 b 80.5 b 60 - 95 5.2 a 3.2 - 13.0
Monticello, Fla. 47.3 a 50.7 a 48.1 a 80.8 b 64 - 111 4.9 a 2.5 - 9.8
Seed source
x
Northern Florida 45.0 a 27.9 a 35.4 a 81.4 a 60 - 101 5.2 b 3.2 - 8.5
Central Florida 37.9 a 32.1 a 34.6 a 83.6 a 67 - 120 3.6 c 2.5 - 4.8
Texas 45.2 a 37.7 a 40.9 a 89.8 a 60 - 107 7.1 a 4.4 - 13.0
Significance
v
Site NS *** * * N/A NS N/A
Seed source NS NS NS NS N/A *** N/A
z
Measurements were based on total plant size (vegetative + inflorescence); 1.0 cm = 0.39 inches.
y
GI = Growth Index = (height + average width)/2.
x
The interaction of site by seed source was not significant at P ≤ 0.05. Main effect means for site
are averaged over seed source, and seed source means are averaged over site.
w
Mean values for Fort Lauderdale, Fla. for northern Florida, central Florida, and Texas seed
sources were based on 3, 3, and 11 plants, respectively.
v
*, ***, NS - Significant at 0.05, 0.001, and nonsignificant, respectively.
15
Table 4. Effect of site and seed source on peak flowering characteristics of black-eyed susan.
Peak flower
(days after transplant) Number flowers at peak
Minimum/ Minimum/
maximum maximum
Site Seed source Number
z
values Number
z
values
Bradenton, Fla. Northern Florida 116.1 a 114 - 128 10.3 a 6 - 16
Central Florida 114.9 a 107 - 128 8.6 a 1 - 12
Texas 116.1 a 107 - 135 9.8 a 3 - 19
Ft. Lauderdale, Fla.
y
Northern Florida 124 .0 b 108 - 156 27.0 a 8 - 46
Central Florida 156.0 a 156 33.3 a 4 - 56
Texas 113.1 b 108 - 115 43.4 a 7 - 84
Jay, Fla. Northern Florida 113.6 a 89 - 160 19.8 b 9 - 35
Central Florida 112.1 a 110 - 124 19.0 b 10 - 32
Texas 105.1 a 89 - 117 48.0 a 32 - 71
Monticello, Fla. Northern Florida 99.7 b 88 - 104 23.2 a 7 - 55
Central Florida 113.8 a 102 - 171 28.3 a 17 - 47
Texas 96.9 b 92 - 104 34.3 a 14 - 56
Significance
x
Site NS N/A * N/A
Seed source NS N/A NS N/A
Site X seed source *** N/A * N/A
z
Means with different letters, within a site and column, are significantly different (P ≤ 0.05).
16
y
Mean values for Fort Lauderdale, Fla. for northern Florida, central Florida, and Texas seed
sources were based on 3, 3, and 11 plants, respectively.
x
*, ***, NS - Significant at 0.05, 0.001, and nonsignificant, respectively.
17
Table 5. Summer and fall 1998 survival of black-eyed susan from different seed sources.
Percent of plants surviving to the beginning of:
Seed source June July August September October November
Bradenton, Fla. (AHS Heat Zone 10)
Northern Florida 100 100 100 80 80 70
Central Florida 100 100 100 100 90 90
Texas 100 100 80 30 0 0
Ft. Lauderdale, Fla.
z
(AHS Heat Zone 11)
Northern Florida 100 100 100 66 33 33
Central Florida 100 100 100 100 66 66
Texas 100 100 64 9 9 0
Jay, Fla. (AHS Heat Zone 9)
Northern Florida 100 100 100 0 0 0
Central Florida 100 100 100 0 0 0
Texas 100 100 100 0 0 0
Monticello, Fla. (AHS Heat Zone 9)
Northern Florida 100 100 100 80 60 20
Central Florida 90 90 90 90 90 90
Texas 80 80 80 20 0 0
z
Percentages for Fort Lauderdale, Fla. for northern Florida, central Florida, and Texas seed
sources were based on 3, 3, and 11 plants, respectively.
