This is a native clonal shrub that often forms impenetrable spiny thickets in forest understories; rarely the stems will reach upwards of 6 m.  The completely unarmed forma impuniens Fassett was described from Juneau Co.  Prickly-ash is a common shrub in the southern part of the state, ranging north mainly along major river systems.  It is apparently absent (or has been ignored by collectors) in an area between the Black and Wisconsin Rivers as well as a huge swath extending from eastern Dane Co. and western Dodge Co. through the Central Sandhills Ecological Landscape and the eastern edge of the Forest Transition Ecological Landscape.  It is common in the northeast but almost entirely absent from Kewaunee Co. and Door Co., save for one collection from the latter.