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

Germination trials of three seedlots were conducted over a temperature gradient for 14 days to determine the optimal germination temperature for the Black-eyed Susan (Rudbeckia fulgida Ait.). The optimal germination temperature for R. fulgida seeds was 30 ± 1C. All three seedlots began germination (radicle emergence) on the second day at 30.2C. By day four, all seedlots sur-passed 50% germination, with three seedlots germinating 53%, 52%, and 73%. Mean germination percentages were higher between 28.3 and 32.6C than at temperatures above or below this range. Significantly higher germination percentages and enhanced germination rates attained at the elevated temperatures may save time, cut production costs, and decrease exposure to detrimental pre-emergent pathogenic fungi.

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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.