'Chelsea chop' method prolongs flowering in some perennials - Victoria Times Colonist
The Chelsea chop can be used on substantial clumps of garden phlox (Phlox paniculata), Monarda (bee balm), Heliopsis, Echinacea and similar plants.
British Columbia Wheeley Hall Barry Willoughby Robin Denning Brentwood Patrick Church Esquimalt United Church
Source: timescolonist.com