Germination, and Seedling and Rosette Development of Flodman Thistle (Cirsium flodmanii)
Maximum germination of flodman thistle [Cirsium flodmanii(Rydb.) Arthur ♯3CIRFL] occurred at alternating temperatures of 10 to 20 and 20 to 30 C. Seeds germinated (20%) in 1.7 M NaCl. Light was important in seed germination; however, its absence could be overcome by adding 8.6 × 10-5M GA3(gibberellic acid) to the germination medium. The greatest seedling emergence occurred when seeds were planted on the soil surface and was lower when seeds were buried at any depth in the soil. Osmotic potentials at −0.5 MPa and greater reduced germination, but 3% of the seeds germinated at −1.3 MPa. Flodman thistle seedlings tolerated average plant water potentials of −0.9 and −1.1 MPa, but they died when the water potential was decreased to −1.5 MPa. Flodman thistle seedlings 43 days old and with four true leaves resprouted after topgrowth removal. Regrowth was evident on 75% of the clipped plants 13 days after initial topgrowth removal. Flodman thistle rosettes spread more rapidly and rosette survival was enhanced more in a weed-free nursery than in a weedy pasture.