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Jeffrey G. Norcini, James H. Aldrich, Mack Thetford, Kimberly A. Klock-Moore, Michelle L. Bell, and Brent K. Harbaugh

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 American Horticultural Society (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.

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Clydette M. Alsup and Pamela B. Trewatha

In two experiments, seedlings of black-eyed susan were transplanted into 15-cm pots and after 1 week received one of the following treatments: media drench application of 0.1, 1, 10, or 100 mg·L-1 of paclobutrazol or pinching back of terminal growth once, twice, or three times. After plants reached salable size, plant height, lateral branch length and number, and flower counts were taken, and plants were harvested for dry weights. In the first experiment, all pinching treatments and 10 mg·L-1 paclobutrazol reduced plant height and increased lateral branching. Flower count at harvest was enhanced by paclobutrazol and reduced by pinching, due to delayed development of inflorescences. Lateral branching and flower bud count were greatest in the second study on plants receiving three pinches. The 100 mg·L-1 paclobutrazol-drenched plants had lowest height, dry weight, and bud count and were severely stunted. The most attractive plants appeared to be those that received the 10 mg·L-1 paclobutrazol drench treatments.

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Amy M. Fay, Mark A. Bennett, and Steven M. Still

Low-vigor seeds of black-eyed Susan (Rudbeckia fulgida Ait.) primed in aerated -1.3 MPa KNO3 for 7 days at 30C in darkness had double the total germination percentage at 30C and one-half the mean time of germination as nonprimed seeds. Priming the seeds in polyethylene glycol rather than KNO3 generally resulted in lower total germination percentage and longer mean time of germination. Osmotic priming increased total germination percentage and germination rate of seeds germinated at 21.9 to 32.2C, but the priming benefit on total germination percentage was greater at ≤27.6C. Total germination percentage of primed and nonprimed seeds was highest at 28.8 to 32.2C.

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Jeffrey F. Derr

Tolerance of transplanted black-eyed Susan (Rudbeckia hirta var. pulcherrima Farw.), lanceleaf coreopsis (Coreopsis lanceolata L.), shasta daisy (Chrysanthemum × superbum Bergmans ex. J. Ingram), purple coneflower [Echinacea purpurea (L.) Moench.], and blanket flower (Gaillardia aristata Pursh) to preemergence herbicides was evaluated in container trials. Herbicides were applied at the maximum use rate and twice the maximum use rate. Dithiopyr, pendimethalin, and prodiamine provided excellent control of spotted. spurge (Euphorbia maculata L.) and yellow woodsorrel (Oxalis stricta L.) with little injury to the five herbaceous perennials. DCPA, oxadiazon, and metolachlor were tolerated by all treated species, but these chemicals provided lower control of one or both weed species. Oryzalin, isoxaben + trifluralin, and napropamide caused unacceptable injury and shoot fresh-weight reductions in some of the perennials at one or both application rates. Chemical names used: dimethyl 2,3,5,6-tetrachloro-1,4-benzenedicarboxylate (DCPA); S,S-dimethyl 2-(difluoromethyl) -4-(2 -methylpropyl)-6-trifluoromethyl-3,5-pyridinedicarbothioate(dithiopyr);N-[3-(1-ethyl-1-methylpropyl)-5-isoxazolyl]-2,6-dimethoxybenzamide(isoxaben); 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide(metolachlor);N,N-diethyl-2-(l-naphtha1enenyloxy) propanamide(napropamide);4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin);3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethy1)-l,3,4-oxadiazol-2-(3H)-one (oxadiazon); N-(1-ethylpropyl) -3,4-dimethyl-2,6-dinitrobenzamine (pendimethalin); N,N-di-n-propyl-2,4-dinitro-6-(trifluoromethyl)-m-phenylenediamine (prodiamine); 2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzamine (trifluralin).

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Kelly M. Oates, Darren H. Touchell, and Thomas G. Ranney

The genus Rudbeckia (black-eyed Susan or coneflower) consists of ≈30 species, all of which are native to North America ( Armitage, 1997 ; Palmer et al., 2009 ). The genus includes annual, biennial, and perennial species ( Perdue, 1957

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Gina M. Angelella and Megan E. O’Rourke

( Chamaecrista fasciculata ), and showy tickseed ( Bidens aristosa ); the biennual was black-eyed Susan ( Rudbeckia hirta ); perennials included narrowleaf mountain mint ( Pycnanthemum tenuifolium ), lanceleaf coreopsis ( Coreopsis lanceolata ), wild bergamot

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Heather Kalaman, Gary W. Knox, Sandra B. Wilson, and Wendy Wilber

advertised pollinator plant, spotted beebalm ( Monarda punctata ), 587 of 838 respondents (70.1%) were able to correctly identify an image of this floral resource. Similarly, when shown a photo of a black-eyed susan ( Rudbeckia hirta ), 744 of 841 respondents

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Anthony M. Ortiz, Brent S. Sipes, Susan C. Miyasaka, and Alton S. Arakaki

. bicolor nothosubsp. drummondii cvs. Bale All, Bale All III, Baler, Graze-All, Piper, Sordan 79, and Tastemaker. The other species group included black hollyhock, elecampane, black-eyed Susan, and sunn hemp. Seeds were germinated in vermiculite and

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James J. Marois and Jeffrey G. Norcini

Survival of black-eyed susan (Rudbeckia hirta) from three regional seed sources was evaluated after inoculation with the pathogenic fungus Fusarium oxysporum in the greenhouse, and after they were planted in fumigated or nonfumigated and irrigated or nonirrigated field plots. The three seed sources were northern Florida (NFL), central Florida (CFL), or Texas (TEX). Plants from the three seed sources were inoculated individually under greenhouse conditions with four isolates of F. oxysporum originally isolated from the roots of diseased black-eyed susan grown in ecotype trials near Monticello, Fla. About 20% of the inoculated plants developed symptoms similar to those observed in the field, but no consistent ecotype or isolate effects were observed. In the field trial, planting beds were fumigated with methyl-bromide and chloropicrin and irrigated with drip irrigation (high input), not fumigated and irrigated, fumigated and not irrigated, or not fumigated and not irrigated (low input). During the first month of the trial, treatment and seed source had a significant effect on survival due to the low initial survival of NFL in the nonfumigated-nonirrigated plots. After the first month, only seed source had asignificant effect on survival, with TEX decreasing rapidly and the NFL population decreasing to a lesser degree. The decline of TEX could not be directly attributed to pests or climatic effects.

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Richard L. Harkess and Robert E. Lyons

Histological and histochemical examination of floral initiation was conducted to determine the pattern of flowering in Rudbeckia hirta, a long-day (LD) plant. Plants were grown under 8-hour short days (SDs) until they had 14 to 16 expanded leaves. Half of the group of plants was moved to LD conditions consisting of natural daylength plus a 4-hour night interruption. Rudbeckia hirta had a pattern of differentiation in flowering similar to that reported in species requiring one inductive day for initiation. Rudbeckia hirta required 8 LDs for evocation and 18 LDs for completion of initiation. Involucral bracts initiated after 18 LDs, after which the receptacle enlarged and was capped by a meristematic mantle of cells signaling the start of development. Floret primordia did not initiate, even after 20 LDs. Increases in pyronin staining were observed in actively dividing cells of the procambium, leaf primordium, and corpus of the vegetative meristems. After 8 LDs, the pith rib meristem stained darkly, a result indicating the arrival of the floral stimulus. An increase in pyronin staining was also observed in the meristematic mantle covering the receptacle after 18 LDs, a result indicating increased RNA levels.