The most useful plants for spring phenology studies are:
- Easy to identify
- Broadly distributed
- Naturally occurring species with a short bloom period
These key “indicator” plants tend to flower as they accumulate heat, which means that after warmer winters and springs they flower earlier than average. Non-native PlantWatch species, such as lilac and dandelion, also were selected because they are common species across Canada and have a long history of use in phenology studies.