Aug 30 2014
Can a thistle be good? This one is.
Swamp thistle (Cirsium muticum) is practically smooth. Its hollow 6-foot stem has no spines and its deeply cut leaves look pointy but aren’t very sharp. It is very beautiful with big purple flowers that attract bees, butterflies and hummingbird clearwing moths.
Compare this native biennial to other big thistles and this is the one you’ll prefer to touch. Pasture thistle (Cirsium pumilum) is more prickly though it smells very sweet. Field thistle (Cirsium discolor) and non-native Bull thistle (Cirsium vulgare) are so spiny they’re absolutely scary. Wear stout gloves!
The easiest way to identify Swamp thistle is by its bud which looks cob-webby with fine white hairs. Here’s a closeup.
Swamp thistle is native to eastern North America from Labrador to Louisiana (and Texas) where it grows in swamps, wet woods and thickets.
I photographed these two at Jennings Prairie in Butler County, Pennsylvania earlier this month.
(photos by Kate St. John)