At Mary Dunn Pond we found Salix cinerea along with S. atrocinerea . Some botanists prefer to treat them as two subspecies of the same European species, Salix cinerea . However, Mary Dunn Pond has turned out to be a good example where one can see both willows growing together and yet clearly distinguishable from each other. This confirms the opinion that they are distinct species. Gray willow has been considered invasive in some countries. However, it's been mostly understood in the broad sense, including rusty willow ( Salix atrocinerea = S. cinerea ssp. oleifolia .) In our area S. atrocinerea might be actually much more aggressive than S. cinerea , which seems not as common.