The Royal Horticultural Society has held the annual Chelsea Flower Show every year at the end of May since 1913 in Chelsea, London. There is a garden task that corresponds to these dates that has become known as the Chelsea chop. We spoke of this last year, but it is good to have a timely reminder once again because the window of opportunity is short.
The Chelsea chop helps to prolong the blooms of summer and fall flowering perennials such as tall phlox and heliopsis. The chop involves cutting back some of the stems of the plant by six or eight inches in late May or early June. These cut stems produce multiple stems of buds that flower later than the uncut stem, extending the bloom time of the plant.
In instances where I have multiple plants of the same variety, I will sometimes cut back entire plants while leaving others alone. This practice is best when completed before mid-June, so chop-chop!