Seeds of native species of perennial phlox often germinate poorly for producers of native plants. To determine seed treatments that might improve germination, we conducted a study on the native longleaf phlox (Phlox longifolia L. [Polemoniaceae]). Seed treatments included a 7 °C (45 °F) cold treatment, a 21 °C (70 °F) warm treatment, 10 or 20 ml/l liquid smoke, 1000 or 2000 ppm KNO3, 100 or 500 ppm GA3, and a 21 °C distilled water control. Seeds were placed on filter paper in Petri plates and germinated in the dark. All treatments except the 7 °C stratification were incubated at 21 °C for 4 wk. At least 90% of Phlox longifolia seeds germinated during the 7 °C cold treatment within 7 to 10 d and had the highest germination percentages of all treatments. The 500 ppm GA3 treatment induced approximately 37% of P. longifolia seeds to germinate in 4 wk, but germination in GA3 treatments was characterized by cotyledons emerging first with few radicles emerging. The 21 °C stratification, liquid smoke, or KNO3 seed treatments failed to induce germination. Germination percentages of P. longifolia seeds in all treatments increased sharply when seeds were moved from 21 °C and into the 7 °C refrigerator. Seeds of P. longifolia exposed to a 7 °C cold treatment germinated quickly at high percentages (> 90%), making this treatment practical for nursery propagation of this native perennial.


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pp. 80-88
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