witch’s broom
n.— «Others are freaks of nature that arrived on a “witch’s broom.” That’s the term for a mutation that sometimes occurs on the branch of a normal tree and is characterized by a tight, dense mass of abnormally small foliage.» —“Dwarf and miniature conifers have a place in today’s landscape” by Valerie Sudol Star-Ledger (Newark, New Jersey) Dec. 10, 2008. (source: Double-Tongued Dictionary)