Bidens cernua is also known as Nodding Beggarticks. It can grow very tall and is usually found in wet sites, along ponds, rivers and lakes. It’s native to North America and parts of Europe. You may find ducks feeding on the seeds of this plant after the flowers begin their decline. Bloom time is the end of August through September in the northeast U.S. I found these on September 16, 2022 in CT.