This is definately a question of personal choice and what works best for your situation. Our season is short up here which for me means preparing ahead for the next season begins in August. I have 3 beds rotating for sdlg's - new spring planted, then 1st year to bloom and 2nd year to bloom and 4 rotating for selects. Beds get cut back starting with the 1st year to bloom sdlg's and previous years select sdlg beds.New spring planted seedlings get weeded, not trimmed. I start the end of August, just as I finish pollenating and bloom is winding down. Doing it at this time gives me a chance to see how each one has done over the season and give the beds a thorough weeding. Scapes with pods are much easier to find when foliage is cut 10 - 12 inches, you just have to be careful when trimming not to cut them off!
Once pods are off the 2nd year bloomers the selects are dug, trimmed, moved and the rest of the seedlings in that section dug and composted to prepare the bed for the new sdg's next spring.
Then I move down to the front display garden and do the same trim & weed. This is also the time for fall orders to begin shipping and digging, dividing and rearranging of the plants in beds and a good weeding to be done. I hand weed everything here starting as soon as the ground thaws to when the first scapes come up, then I stop so as not to break scapes off while bending for weeds.In the 6 to 8 weeks of bloom it is amazing how the weeds grow all hidden by foliage.I can do fan counts on all plants and update maps easier when they are trimmed, something which can not be done once it snows, then I can work on my seedling book, sale listings, garden list etc. for the next year during winter.The last to be cut are my other perennials. All that's left to do now is update maps, fan counts, flip the compost pile and begin splitting wood to dry for next year, the crisp fall days are perfect for splitting wood.
