Musk Thistle (Carduus thoermeri) Seed Production

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Abstract
Seed production was studied near Lincoln, Nebraska for musk or nodding thistle (common names used for large-flowered species ofCarduus – C. macrocephalusDesf.,C. nutansL.,C. thoermeriWeinm.). Four levels of seed maturity were studied from separate groups of plants with the heads harvested at the full-bloom stage, 2 days after full bloom, 4 days after full bloom, and at full maturity. The first heads to bloom (terminal) averaged about 1000 seeds/head and the last to bloom (lateral branches near the base of the plant), ca. 125. Plants produced only 26 good quality seeds/plant when the heads were all clipped at the full-bloom stage, but the plants with heads allowed to go to maturity produced 3580 of the good quality seeds/plant. Plants with heads clipped at 2 and 4 days after full bloom produced 72 and 774 good quality seeds, respectively.