Dr Ian Plummer
WHAT? The ‘plummer’ is a unit of lawn speed measurement allowing the speeds of various lawns to be compared.
WHY? Are today's croquet players better than those in history? Why were so few peels done at a particular tournament? Are modern lawns easier?
These questions are near impossible to answer when we have no measure of the difficulty of lawns. There are many factors affecting play such as: how flat the lawn is, the width & sturdiness of hoops, the texture and variation of grass, etc. The aim of measuring lawn speeds is to quantify one aspect of lawn difficulty.
The difficulty of playing croquet increases as a lawn becomes very fast (smooth) or very slow (shaggy). A lawn is very slow/unplayable if it is 8 plummers or less, or very fast /difficult if greater than 13 plummers.
HOW? The speed of a lawn is taken as the time for a ball struck the length of the lawn from the boundary line at one end to just stop on the boundary line at the other (35 yards). The time in seconds is the plummer value and is generally quoted to the half second. In practice balls will stop near the far boundary and their length can be estimated. A graph on the back of an envelope can be produced to interpolate the time at 35 yards. More information here.