What is "umbels"

Usage examples of "umbels".

The azaleas succeeded to the anemones, the orchis and trillium followed, then the yellow gerardias and the feathery purple pogonias, and finally the growing gleam of the golden-rods along the wood-side and the red umbels of the tall eupatoriums in the meadow announced the close of summer.

Then she noticed several more dried flower umbels, and while she was digging them, she saw some thistle stalks, crisp and juicy after the spines were scraped off.