as·per·ous | /ˈasp(ə)rəs/
Running carelessly over rough ground, you could trip on some asperous rock and fall into a patch of Sonchus asper, which would be exasperating. Asperous refers to a coarse, prickly, or scabrous surface. The term comes to us from the Latin asper, meaning rough or scabby, as does asperity. To asperate is to roughen or irritate, from which we derive exasperate.
For Latin speakers, asper could refer to all manner of harshness, from rancid wine to foul weather. In botany, asperous describes plants that are rough or lumpen to the touch such as the knurled* trunk of an ancient tree. Asper is a distinct epithet for coarse species such as the Sonchus asper, commonly known as the spiny leaved sow thistle. Spinescent plants may also have the epithets acut (Latin for sharp) or acanth (Greek for spine).
Not all spinescent plants are asperous for protection – the primary purpose of spines for many xeric species such as cacti is to retain moisture. True plant spines are derived from leaf tissue, whereas thorns form from the stem. Prickles are neither leaf nor stem but project directly from the plant’s dermis and are more akin to coarse hairs. Philosopher Arthur Schopenhauer, who famously mused there was “no rose without a thorn”, would have been aghast to discover that roses don’t actually have thorns – they have prickles.
* Knurls are the rough, leprous looking lumpy outgrowths common to the trunks of many ancient trees.
Introduction Aeolian Alpenglow Apricity Asperous
Benthos Crepuscular Crispate Crown shyness
Desire lines Dreich Endragoned Edgelands
Frondescence Fumarole Gluggaveður Gossamer
Karst Komorebi Lawrence Long acre
Machair Monkey’s wedding Moonglade
Psithurism Quartz Rakuyou Roaring forties
Snag Soft estate Specular, diffuse and pellucid
Spoondrift Steam fog Swash zone Sylvan
Tellurian and thalassic Terracettes Uliginous