AKA O. compressa. Given that this species is actually native from Connecticut all the way to Montana, I don't know why AHS claims cold hardiness only to USDA zone 11. Just another example of the importance of consulting multiple sources whenever possible.
May cause contact dermatitis even if you avoid the visible spines.
Suitable as a small-scale groundcover. Clay tolerance is conditional on good drainage.
Sources: Sunset, Missouri BG, NCSU.
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