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When (& Why) to Remove Last Year’s Growth in your Garden

Feb 3

Our staff horticulturist, Kyle Cheesborough, is busy clearing old growth in the cemetery. He explains why this is important and when it should be done below.

kyle trimming

Common garden practice tells us that when the first hard frost hits, we should pull out the pruners and get to work removing all dead leaves and stems leftover in our gardens from the recently ended growing season.  Though this may be the way gardeners have approached the onset of winter in the past, there are many reasons to leave those crunchy, brown leaves hanging on for a while.  Many of our native insects and animals use dead and decomposing leaves, twigs, roots and seeds as important survival sources, whether it be for nourishment, shelter or nesting.  There are a great number of butterflies and moths that hibernate through the winter, using leaf litter as a cover for warmth and camouflage.  Caterpillars wrapped tightly in their cocoons waiting for warm spring weather often hide themselves among the dead plant matter for protection from potential predators and other hazards.  Many of our native bees will take advantage of pithy, hollow stems left from dormant perennials to carve out a nesting hole, with their eggs hatching and emerging in the spring.

Winter HibiscusThalia (2)

Plants like our native rose mallow (Hibiscus lasiocarpos) or marsh milkweed (Asclepias incarnata) leave behind perfect stems for such insects once the plant has gone to bed for the winter.  There are a great many small mammals, reptiles and amphibians that will use thick leaf litter and twigs to roost, tucked safely away from predators and from the harsh winter winds.  Birds, probably our most prevalent winter residents, find myriad uses for the dead matter left behind by our perennials, shrubs and trees.  Winter nesting species need twigs, dead leaves and stems to construct nests.  When the usual buffet of insects and fruits has become scarce in the dormant winter season, seedheads on such plants as coneflower (Echinacea), goldenrod (Solidago), and our native grasses (Andropogon, Schizachyrium, Sorghastrum, Sporobolus, etc.) are a vital food source for birds in the winter.  Many gardeners remove the dead material for aesthetics, but many others remove detritus because they believe this is the healthy way to raise their plants.  In reality, leaving dead leaves and stems until later in the winter has little-to-no effect on the overall health of most perennials.

Winter Foliage (2)

With that said, allowing decomposing material to stick around for too long can begin to build up a thatch layer, eventually impeding the healthy growth of garden perennials.  The wildlife conscious gardener should look at leaving a third of their twiggy stems, and most of the dead, leftover leaves from smaller perennials until late winter, with mid-February being a good target for getting things tidied up in the garden.  However, certain plants do benefit from a haircut a little earlier, such as the increasingly popular sedges (Carex), which actually begin to put on new growth in mid-to-late-January.  These should be trimmed around late January, with care being taken to not cut into the newly emerging leaves.  Can’t stand the idea of all that brown in your garden all winter long?  Consider designating a portion of your garden as a sort of wildlife safe-haven, filled with dead leaf matter, twigs and stems collected while doing your clean-up – maybe even plant a taller perennial or two with the intent of leaving the upright, pithy stems through the winter.  Remember, just as we humans tuck ourselves away into our cozy, heated homes for the cold winter months, our local critters also need a place to shelter themselves from the harsher conditions of winter.

Kyle trimming 1

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