I never cut my perennials right back at this time of year but, once the flowers have began to fade and look tatty, then I always dead head the flowers and tidy up dropped foliage,
If there are more flower buds on the plants, then make sure you leave these buds to form into nice flowers. Some perennials have a second flush of flowers and in time, you will get to know which types do this, so you don't cut off the second flowering, some need to be cut right back to encourage second flowering but without knowing what you have growing, Go for a tidy up, snip and tie foliage in to keep tidy and prevent from falling over. I always give mine a feed to help them build up energy after the work the plant have done growing from spring, producing flowers and fighting for survival with hot weather, lack of water or high winds, don't feed after end of August or any new growth wont get a chance to harden off before winter starts and the new foliage could be killed off with frost. I always let my foliage die down till late Autumn as the foliage dying down helps put goodness back into the plants, after the greenery turns brown or collapses then cut it off IF you don't want the birds to feed on seeds or you don't want to collect the seeds.
For perennials the best time to prepare them for giving off their best is spring when the plants are getting going and need feeding, weeding, staking and maybe even splitting a large clump up into smaller pieces,
for this year, take pictures of the flowers /plants then you will be able to identify them in the future, I always think taking over someone else's plantings is great so long as you take your time before you rip it all out as it takes a whole year to find out where bulbs are growing, where shrubs are and how they look in flower, and perennial borders etc are alive and need time to show what they are worth and do you want to move things around the next year. I would go to the book store or local library for books on garden plants perennials / shrubs etc then the pictures in the books will help you identify what you have, as a rough guide an Iris will require the same treatment regardless of colour so long as you know IF it is a bulb, tuber or some other growing root system, a rose regardless of colour requires the same pruning regime so long as you know IF it's a climber, shrub or bush, so books will guide you and you will learn what your plants need and how to treat them. good luck. WeeNel.
