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.
Jeffrey G. Norcini, James H. Aldrich, Mack Thetford, Kimberly A. Klock-Moore, Michelle L. Bell, and Brent K. Harbaugh
Jeffrey G. Norcini, Mack Thetford, Kimberly A. Moore, Michelle L. Bell, Brent K. Harbaugh, and James H. Aldrich
Evidence is presented that native populations of Rudbeckia hirta L. (Blackeyed Susan) may be adapted to regional conditions. Two Florida ecotypes, one from north Florida (NFL) and one from central Florida (CFL), were better able to withstand the low fertility sites under three AHS Heat Zones (9, 10, 11) in Florida than were plants grown from Texas (TEX) seeds. Plants from TEX seed were the largest and showiest (generally the greatest number of flowers; largest flowers) but the shortest-lived. Most of these plants did not survive beyond August (about 6 months after transplanting) regardless of site. The CFL plants were especially tolerant of flooding conditions at Ft. Lauderdale. Under garden conditions, CFL Black-eyed Susan may be a highly desirable wildflower for subtropical or tropical summers.