Fall perennial garden cleanup--to do, or not?

11/13/2001
Fall perennial garden cleanup--to do, or not?

Before all you fall garden clearcutters head out to your perennial patch with your tools of destruction in hand...hold on a minute. The perennial garden at the end of the season is not a lawn ready for its final mowing.

Here's why. First of all, if you cut down all your perennials at ground level now, your garden will look utterly barren through the winter--just a blank space which--if you're lucky--will be covered by snow. Otherwise, just a blank space of--well--mud, or, okay, mulch.

If you refrain from clearcutting the perennial garden in the fall, you'll have a rich tapestry of plant skeletons and seed heads to view throughout winter. Although not as showy as the lush greenery and vibrant blossoms of summer, the perennial garden in its winter clothing has a haunting and subtle beauty not to be missed. Forms of plants--fountains of now tawny leaves, plumes of grasses, masses of deep umber seed heads--become central to the tableau, as does its palette of soft and subtle tans, buffs, golds, greys, umbers, and sienna browns. And as winter progresses, these skeletons will be embellished by the crystalline tracery of hoarfrost and puffy caps of snow, providing you with an ever-changing seasonal painting to view.

Not only are all those seed heads lovely to look at, but they're even more attractive when enlivened by droves of over-wintering birds which without fail will descend to feed on them, and even shelter in the harbor of the dead foliage. Scores of perennials provide protein- and oil-rich seeds for birds. The giant perennial sunflower pictured above (which blooms in October and November), willowleaf sunflower, coreopsis, asters, liatris, blackberry lily, coneflowers of all kinds, and many others provide a natural (and free) feast for your avian friends.

Not only do all those dry plant skeletons look a heck of a lot better than a clearcut void, and feed the poor, hungry birds, but they also provide the best possible insulation for the crowns of your perennials through harsh winter freezes. The hollow, dry stems and the papery foliage maintain an airy, insulating space under the snow, which is just the ticket for protecting the sensitive crowns of perennials. (Isn't nature thoughtful?) This natural insulation is far superior to covering your perennials with shredded wood mulch, as is so often--and mistakenly--recommended. Wood mulch becomes waterlogged and heavily matted down (anaerobic) through the winter--conditions which spell death to many perennials, and offer little to no insulating value. Especially perennials that are prone to "rotting out" through a wet winter fare much better when left uncut.

Finally, some perennials, such as lavender, iberis, bearberry, and Russian sage, are actually "subshrubs" that have woody stem bases with overwintering buds. These perennials will probably be killed by a severe fall pruning. Instead, wait until early spring and scratch the epidermis, or bark, of the stems. If the tissue is white beneath, the stem is alive. If it is dark brown or blackened, and the bark slips easily, it has been winterkilled. Prune these perennials down into live wood.

And, don't forget, many perennials are evergreen or semi-evergreen! These, of course, should be spared at all costs, for their green persistent leaves are a welcome site through the dreary barren months. Hellebores, bergenias, and European ginger are just a few examples of this precious category of perennials.

As always, there are exceptions to the rule, even to my rule of laissez faire in the fall perennials. A few perennials which are disease-prone--herbaceous peonies come to mind--should be trimmed down and their foliage destroyed, as should plants that just sort of turn to black slimy mush after a freeze. Lobelias and fall-blooming anemones fall into that category.

So just when do you clean up the garden, you're probably asking, impatiently tapping your foot. The answer is on that first unseasonably warm day in late winter or early spring, when, about to expire from cabin fever, you're just dying to go outside and do something. Grab your shears, your tarp, your wheelbarrow, your shears, step into those mudboots--and go to it!

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