The Impacts of Temperature, Soil Type and Soil Herbicides on Seed Germination and Early Establishment of Common Milkweed (Asclepias syriaca </i L.)

The effects of different temperatures (20 °C, 25 °C, 30 °C, 35 °C and photoperiod 26 °C/21 °C), types of soil (sand and loam) and soil herbicides (oxyfluorfen, terbuthylazine and mesotrione) on seed germination percentage, germination rate, as well as seedling length and weight of common milkweed (Asclepias syriaca L.) were examined. Over a period of ten days, germinated seeds were counted daily, and seedling length and weight were measured on the final day and germination rate calculated. The results indicated that temperature was the factor that significantly affected the percentage of germinated seeds of common milkweed, seedling length and germination rate, while it had less influence on seedling weight. The results showed that the alternating day/night temperature of 26 °C/21 °C also had a significant impact as the percentage of germinated seeds was the highest at that temperature on both soil types (sand: 71.3%; loam: 61.3%). Data regarding the herbicides tested (oxyfluorfen, terbuthylazine and mesotrione) showed decreasing germination percentage and seedling length with increasing herbicide concentrations on both soil types. Their effect was weakest on seedling weight. Tested herbicides are usable in control of common milkweed at the stages of germination and early establishment.