Don't be mimsy with the scissors!

Avoid the temptation to just snip off the old flowers of Leucanthemums (Shasta Daisies): you will not get any more blooms on the stem so you should cut it right back to base.

The same applies to the similar looking Tanacetums, Anthemis, and, later in the summer, Coreopsis, Echinacea, Rudbeckias and Heleniums.