Fall is a wonderful time in the garden, full of color and activity. Leaves are turning, asters and goldenrods are blooming. Small mammals are skittering around, gathering food stores. Birds are fattening up on seeds and berries while bees and butterflies are flower hopping, collecting nectar and pollen to provision their nests. There is a lot to do in the garden … or not.
For gardeners who still want to play in the dirt, fall is a fine time to divide spring and summer blooming perennials. Division may seem counterintuitive — my big beautiful plant! — but for most perennials it is rejuvenating, giving crowded plants room to spread their roots and leading to renewed vigor, better bloom, and longevity. Divide four to six weeks before the first frost, a moving target to be sure, but generally the third or fourth week in October. Replant your divisions to fill in your garden and share them with friends. Who doesn’t like free plants?
If division is good, it follows that fall planting is as well. Cooler temperatures and fall rains help reduce transplant shock giving newly planted perennials a chance to establish roots before winter. Lucky for you, nurseries steeply discount perennials after Labor Day and a few organizations have fall plant sales. (Grow Native Massachusetts, Middlesex Conservation District, Somerville Garden Club—check their websites for listings).
However, if you are not dividing your perennials, kindly leave them alone. Do not cut them back, their usefulness in the garden is far from finished. The dead stalks shield and insulate the crown of the plant over the winter and come spring support the new growth which will soon hide them from view. The fading stems provide habitat for overwintering insects to nest, hibernate and pupate. Birds will also benefit from your more relaxed approach to fall cleanup, picking through the stalks looking for insects and gleaning seeds. If you feel strongly that the stems are too tall and raggedy, you can cut them back a bit, leaving about 18 inches of stem standing.
Consider this. All spring and summer you encourage your plants to grow full and strong. You water, you mulch, you amend the soil. Your plants take all your effort and costly inputs and, with the addition of sunlight, they do their bit. They photosynthesize, make new leaves, branch out and grow taller. They produce flowers and seeds and fruits. So much plant material. So much energy! Where does it all go when perennials die back and leaves fall?
That, dear gardener, depends on you.
You could have your lawn service people come along with their leaf blowers and rakes and impressive giant vacuums. They will happily siphon up all that goodness (and anything else that is not nailed down) leaving your beds completely, unnaturally, bare; leaves, flower stalks, caterpillars, spiders and other insects, all inhaled. They will cart it all away in their trucks, far from your garden. What happens to it all? Perhaps it will be made into compost which you can buy next year to spread on your beds to add nutrition and organic material to your soil. (In Belmont, curbside yard waste is picked up by WM waste management service and hauled to a facility in Tewksbury.) Worst case, it will go to a landfill.
Or, after all the effort you and your plants put forth, you could eliminate the middleman and keep all that goodness in your garden, supporting the cycle of life that makes your garden thrive. Leaf litter is wonderful stuff, holding in moisture and insulating and protecting perennials from temperature swings before breaking down to build and enrich the soil. And, in these days of jumping worms, invasive weeds, and other pathogens (beech leaf disease, for example), it is a real benefit to know that you have not inadvertently brought any of that into your garden. Of course, leaves must not be allowed to suffocate your lawn. Mow them into the grass where they will give organic matter and nutrition to your lawn free for nothing.
Dorothy gardens in Belmont where she lives with her husband, Steve, and their dog Jasper. She has six grandchildren — all perfect by definition — and has enjoyed introducing them to gardening. She has an abiding interest in nature and is always amazed by the wonders to be found in her own backyard.