Bristle Thistle (Cirsium horridulum) is in the Sunflowers, Daisies, Asters, and Allies family (Asteraceae). Across the U.S., iNaturalist users have logged 3,275 research-grade flowering observations of it in our sample, peaking in April.
Nationally it blooms mainly from March to May, but timing varies a lot by state and elevation — see the table below.
When to photograph Bristle Thistle: observations by month (U.S.)
About Bristle Thistle
Cirsium horridulum, called bristly thistle, horrid thistle, yellow thistle or bull thistle, is a North American species of plants in the thistle tribe within the sunflower family. The species is native to the eastern and southern United States from New England to Florida, Texas, and Oklahoma as well as to Mexico, Belize, Guatemala, Honduras, and the Bahamas.From Wikipedia via iNaturalist — article, CC BY-SA.
Bristle Thistle by state
| State | Observations | Peak month | Main season |
|---|---|---|---|
| Texas | 1,063 | April | Mar–Apr |
| Florida | 645 | March | Mar–Apr |
| Mississippi | 349 | April | Mar–Apr |
| Georgia | 225 | April | Mar–May |
| Louisiana | 181 | April | Mar–Apr |
| North Carolina | 174 | April | Apr–May |
| Virginia | 140 | May | May–May |
| South Carolina | 121 | April | Mar–May |
| Alabama | 116 | April | Apr–Apr |
| New Jersey | 80 | May | May–May |
| Maryland | 63 | May | May–May |
| Arkansas | 38 | April | Apr–May |
| Delaware | 27 | May | May–Jun |
| Massachusetts | 17 | June | Jun–Jun |
| Tennessee | 12 | May | May–May |
| New York | 9 | June | Jun–Jun |
| Oklahoma | 8 | April | Apr–May |
Main season = months with at least 30% of the state's peak-month count.
Related wildflowers (Sunflowers, Daisies, Asters, and Allies)
black-eyed Susan
Common Yarrow
White Snakeroot
Chicory
Lawn daisy
Philadelphia fleabane
Pearly Everlasting
Blue Mistflower
Photography tips
- Photograph flowers on calm, overcast mornings to avoid wind blur and harsh shadows.
- Get low: a shallow depth of field (f/2.8–f/5.6) isolates a bloom against soft color.
- Stay on trails — trampling meadows kills plants and ruins next year's display.
- Try a kaleidoscope abstract of a single bloom with our online kaleidoscope tool.
FAQ
When is the best time to photograph Bristle Thistle?
Nationally, April has the most observations, with the main season from March to May.
Where is Bristle Thistle most often seen?
The most observations come from Texas, Florida, Mississippi.