Experts and BHG readers answer.
What makes Forsythia's bloom in fall?
When spring-blooming trees and shrubs bloom in the fall rather than the spring (or in addition to spring bloom), it's usually an indication that the plant was stressed during the growing season so that growth slowed down or stopped, but that growing conditions later improved and they restarted growth. That kick-start of growth is similar to spring, triggering the bloom cycle. It's actually a fairly common occurrence.