An above-ground structure arising from the root system of some wetland species such as swamp cypress (Taxodium distichum), said to be knee-like in this species, assisting the roots to exchange gases with the air when the soil is waterlogged or flooded. See soil aeration.

This definition is abridged from A – Z of tree terms: A companion to British arboriculture.
Read the preface. Order the book.

Previous term | Next term