That tall, prickly plant crowned with a fluffy purple flower in a sunny field is Bull Thistle (Cirsium vulgare). Every part of it seems armed with spines, yet the bright magenta-purple bloom on top is a magnet for bumblebees and butterflies.
What it looks like
Bull thistle grows 0.5 to 1.5m tall on a winged, spiny stem. The deeply lobed green leaves end in stiff, sharp prickles, and even the base of each flower is wrapped in a spiny green cup. The flower head is a dense brush of purple to pink florets about 4 to 5cm across. When the bloom fades it bursts into a white fluff of seeds, each one parachuting away on a tuft of fine hairs.
When and where
- Season: Flowers from early summer through fall.
- Habitat: Pastures, roadsides, vacant lots, trail edges, and overgrazed or disturbed fields.
- Best time: Midsummer afternoon, when the purple heads are open and busy with insects.
A feast on a fortress
Despite its armor, bull thistle is one of the richest food stops in a summer field. The deep flower heads brim with nectar that bumblebees and many butterflies can reach. Later, American goldfinches pluck the fluffy seeds to eat and also gather the soft white down to line their nests, which is one reason goldfinches nest so late in the year, timed to the thistle seed crop.
Spot one this weekend
Bull thistle is Common in open, sunny ground across the region. Look for the tall spiny stalk and bright purple top, but admire it with your eyes, not your hands. Watch a few minutes and you will likely see a bumblebee crawl deep into the bloom.