Sentence:  Cutting back to the same position annually is usually referred to as "pollarding"; cutting nearly to the ground is usually called "stooling". Both are good methods of controlling height and maintaining vigor on plants that would normally grow to a large size. ... Those [plants] that generate many small stems crowded together are difficult to pollard so they are normally <WSD>stooled</WSD>. Some people refer to <WSD>stooling</WSD> as "coppice". 
Meaning of the word marked with <WSD> tags:  To cut down (a plant) until its main stem is close to the ground, resembling a stool, to promote new growth.