[Wikipedia] Self-incompatible: Solidago altissima is self-incompatible, meaning that the pollen from one plant cannot pollinate the female flower parts of the same plant. (link added by Mary Ann Machi)
Calflora:
Information on California plants for education, research and conservation,
with data contributed by
public and private institutions and individuals.
[web application]. 2025.The Calflora Database
[a non-profit organization].Available:
https://www.calflora.org/(Accessed: 03/30/2025).
