To leave perennials uncut for the winter or not, that is the question, or at least one of many worthy of answering to a wider audience. Winter approaches and, as it does, all sorts of things come up. This however, is a perennial question -- literally and figuratively.
There are lots of reasons people cut back their perennial plants in the fall. Some simply want a clean garden during the winter months. Not only do they like the clear slate, but they fear that viruses and fungi and bad bacteria will winter over on the dead parts of plants left lying around. Of course, they lay off perennials that grow new shoots and leaves off last year's wood, such as clematis and mock orange, and don't prune them at all.
Others remove the dead material from selected plants because that is what they were told to do by whoever taught them about gardening. Peonies are the perfect example. We were all brought up by gardeners who were told and then told us that you had to remove peony leaves from the garden in the fall. If you did not, some awful contamination will crop up and ruin the plants the following spring.
Then there is the Alaska justification of taking away the dead parts of plants, fear of freezing the crowns of cherished perennials. The idea is that unless you clean up, water will get into the crowns of plants, especially of hollow stemmed perennials such as delphiniums. The water freezes and thaws and freezes, causing expansion when it does. The crown cracks open and freezes and thaws and rots.
I no longer clean up. First, I can't be the first person to let my peony leaves remain just to see if there was any truth behind the practice of removing them. I suppose if you have tremendous fungal problems preying on your plants in the summer, the leaves there might be a problem. But the spores of fungi are all over the place anyhow. In any case, fungal problems with peonies, and virus problems as well, are rare in Southcentral. We haven't picked up a spent peony leaf or stem in 15 years and our plants are doing just fine.
And, if you think about it, why would cutting off hollow stems help prevent water from getting into the crowns of perennials? It exposes the crowns. In my experience (and I abandoned the cleaning practice a long time ago) by not cutting the stems of spent delphiniums off, you actually have a better chance of keeping water away from the crowns. You are not opening it up to exposure by removing what I now consider Nature's protection.
You can see where this answer is headed. Why clean everything up? That is not the natural way. Sure, you have to be a bit more careful when you do have to clean up in the spring because pulling off dead stems, for example, often will pull up the whole plant.
There are several advantages to not clearing out the perennial beds. First, and I am quite serious (as always), you won't have any trouble locating your favorite plants next spring.
My advice will be to simply break the dead stuff up and use them to mulch the plants they came from. That is what happens in the wild from where all perennials come and it is the second reason to not clean up now. You feed the soil the material the supports the food web of the plant.
If you do insist on cleaning up perennial beds, at least consider using the material to mulch. Clean or not, you do need to mulch perennials. This brings up a second question. How thick should winter mulch be?
Four inches is a good mulch thickness. However, you really can't put too much mulch on beds in the winter. Its too little or none that hurts. The Alaska Botanical Garden lost tons of plants one year when mulching wasn't done. All the mulch does is keep the soil around the plant from going through the many freeze and thaw cycles we have. You can't go wrong. It also feeds the microbes that feed the plants.
Of course, you will have to remove the mulch in the spring in order to let the soil warm up and get plants going, so that should be a consideration when determining how much mulch you really want to put on plants. Four inches of fresh leaves will compact down and should make a sufficient blanket for the winter. This is a minimum for under trees and shrubs where you are trying to get a forest like ecosystem going in the soil.
Finally, going back to the first concern, to clean or not to clean perennial beds, four inches of leaves will cover almost anyone's labels. And, leaving this year's plant matter attached will take care of being able to locate your plants next spring.
Jeff Lowenfels is a member of the Garden Writers Hall of Fame. You can reach him at teamingwithmicrobes.com or by calling 274-5297 during "The Garden Party" radio show from 10 a.m. to noon Saturdays on KBYR AM-700.
AMARYLLIS: NOW IS THE TIME TO BRING THEM TO A DARK, COOL LOCATION AND LET THEM DRY OUT AND GO DORMANT FOR 8 TO 12 WEEKS IN THE DARK AT 50 DEGREES.
POTATOES: GO AHEAD AND DIG THEM UP. THEY HAVE ENOUGH SUGAR. FAUCETS: DONE YOURS YET?
Alaska Dispatch Publishing