The optimal period for sowing seeds of flowering herbaceous plants in USDA plant hardiness zone 5 hinges on achieving proper soil temperatures and moisture levels. This timeframe generally involves either a late fall sowing, allowing natural stratification over winter, or a spring planting after the last expected frost date. The specific timing within these windows depends on the particular species being cultivated, as some benefit from a cold period to break dormancy, while others germinate best in warmer conditions.
Selecting the correct time for sowing significantly influences germination rates and subsequent plant establishment. Natural stratification, achieved through fall sowing, can improve germination for species requiring a cold period. Spring sowing, conversely, benefits species sensitive to frost or those with rapid germination rates. Early establishment of seedlings reduces competition from weeds and ensures plants have sufficient time to mature and flower during the growing season.