Cutting back fall-blooming perennials

As July nears, it is time for gardeners with perennials to think ahead to autumn blooms.

July 4 is the date most often used to cut back fall-blooming perennials so that there are three good months of growing time to produce a flowering specimen with good form. Cutting back perennials later than early July will not give plants the time they need to recover, resulting in lank vegetative growth with no flowers.

Perennials that should be cut back now are late summer or autumn bloomers: asters, chrysanthemums, goldenrod, phlox, Rudbeckia, and sedum.

Autumn-blooming perennials that have not been pruned will become leggy, straggly, and flop around if they are not cut back. Cutting back now causes foliage to become fuller, more compact in growth habit, encouraging branching, which gives a fuller bloom in the autumn because there are more flowering stems.

It may seem too dramatic but think three months in the future, not what the plants look like tomorrow. There are still several months productive growing season to make up for any of foliage that has been pruned away.

Here are steps gardeners can take to prepare plants for a full floral display in the autumn.

There are two approaches: if flowering specimens are wanted to all be the same height, cut back all stems in a clump by the same amount; the usual amount to remove from most stems is one-half. If various heights of a floral display is wanted, cut back some in a clump to one-half and others in the clump by onethird. For a real statement, allow a few to grow without summer pruning. Longer stems will be lanky, leggy, have sparser foliage that towers over shorter, fuller pruned specimens. Longer stems likely will need some kind of support; without support stems will flop over.

At this point, many gardeners who have just reduced their plants by half, may be lamenting the lush foliage that was just chopped off. The clippings do not have to be discarded. Many of the perennials, like sedum, chrysanthemum, asters, phlox will easily propagate by cuttings. Save the terminal stems; cuttings need to have at least four nodes. Remove leaves from the bottommost nodes but allow topmost leaves to remain. Place cuttings in moist potting soil. Keep moist and within a few months, most will have rooted.