restharrow

From rest +‎ harrow, from the idea that the plant's tough roots would stop a harrow (agricultural implement used to break up soil).

• (UK) IPA^(key): /ˈɹɛsthaɹəʊ/

restharrow (plural restharrows)

1. Any of various species of small shrubs making up the genus Ononis, especially Ononis repens, which has pink flowers.
   • 1653, Nicholas Culpeper, The English Physician Enlarged, Folio Society, published 2007, page 238:

     Common Restharrow rises up with diverse rough, woody twigs, half a yard or a yard high, set at the joints without order [...].