Within the space of a day, Rue Anemone (Thalictrum thalictroides) grows from being invisible to attaining its full height. Walk a trail one day and it is nowhere to be seen, the next day it’s up with its first flower opening, starting the race to reproduce. Rue Anemone blooms, produces fruit, then the above ground parts die back, all before the leaves in the trees above them finish opening for the season.
Before opening, Rue Anemone’s flowers resemble tiny rose buds. Pale pink sepals enclose the flowers’ reproductive organs, but quickly open for business.
There may be up to five flowers per plant, arranged in a whorl radiating from the main stem of the plant, with a whorl of leaves directly below the flowers.
The flowers open one at a time, beginning soon after the plant emerges. The petal-like sepals form the outermost circle of each floral display. They may be pure white or retain the hint of pink they showed before the flowers opened. Moving toward the center of the flower, numerous stamens (the male reproductive parts), comprise the next ring in the floral structure. Starting from the outside of this ring and gradually moving inward, the anthers, located at the tips of the stamens, open a few at a time to release their pollen. At the very center of the flower, there is a cluster of female reproductive parts called carpels, or collectively, pistils. The whitish stigmas at the tips of the carpels are receptive, advertising their availability for a pollen deposit.
Within a few days, all of the flowers on the plant open, each at a slightly different stage of development as a result of their staggered opening.
Rue Anemone partners with early flying bees and flies to assist with cross-pollination. Like some other early spring wildflowers, including Hepaticas (Hepatica nobilis) and Bloodroot (Sanguinaria canadensis), Rue Anemone has evolved to provide only pollen as an enticement to these flower visitors. Pollen is an important part of a bee’s diet, and female bees also harvest it to feed to their larvae. Flies of many species also consume pollen; the females of some species require the protein in pollen to enable egg development.
I watched while a Greater Bee Fly (Bombylius major) darted in and out of a Rue Anemone flower. Bee flies have a very long proboscis (mouth parts), perfectly suited to reach and sip nectar that might be out of range for some other flower visitors. Knowing that Rue Anemone doesn’t offer nectar, I assumed the Bee Fly was harvesting pollen, and I was curious to see how she did it.
In the photos below, it appears that the Bee Fly is harvesting pollen with its proboscis. Once pollen is at the tip of its proboscis, a bee fly then mixes the pollen with fluids and sucks it up through its straw-like mouth parts.
In exchange for the meal, the Bee Fly’s hairy body may pick up pollen and deposit it on another Rue Anemone, enabling cross-pollination.
After pollination occurs, fruits develop at the center of the flower. Ants disperse the seeds, enticed by the nutritious food packet, called an elaiosome, that is attached.
Rue Anemone is a delicate looking perennial of wooded understories, usually about 6-8 inches (1 – 2 dm) tall, but its height can range from 4 to almost 12 inches, depending on growing conditions. It is a member of the Buttercup (Ranunculaceae) family, and like other members of this family, the foliage produces a burning sensation if eaten, a survival strategy that discourages herbivores from consuming the plant.
Rue Anemone is native in the eastern half of the United States, and in the province of Ontario in Canada.
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