On average, how can the proper spacing of herbaceous annuals be determined?

The planting label is the most reliable source for determining the proper spacing of herbaceous annuals. These labels typically provide specific guidelines on how far apart each plant should be spaced to ensure optimal growth. This information is based on the plant's growth habits, mature size, and light requirements, which can significantly affect their health and productivity.

While some may suggest a standard spacing of 18 inches or using the size of the planting bed to guide spacing, these methods can lead to overcrowding or inadequate spacing for particular plant varieties. Moreover, spacing the plants the same width as their expected height does not always account for the growth habits or specific needs of different annuals, which can vary widely. Therefore, relying on the detailed information provided on the planting label ensures that you provide the best conditions for each specific plant variety.