Leaving Leaves

Autumn means raking up every last leaf and clearing dead plant material from the yard — or does it?

Photo A (below) was taken in early December 2020. Tree leaves had fallen, and most plants had entered dormancy, except for several green holdouts. Take a closer look at the Virginia native plant garden in Photo B and find a swallowtail butterfly’s chrysalis attached to the dried stem of a white wood aster (Eurybia divaricata).

While the aster did not host and feed this caterpillar, it’s providing critical habitat during the insect’s pupa stage. Many caterpillars develop on a given plant species and then, to avoid predators looking amongst plants where they know prey live, move to a different location to pupate. This caterpillar likely spent the late summer developing on a nearby tulip poplar (Liriodendron tulipifera) and descended to overwinter as a pupa.

To help this maturing butterfly, fireflies, and other hibernating critters emerge, and to help their eggs hatch next spring, the best and wisest practice is to leave as many husks and fallen foliage as possible where they lie. Raking, blowing, or otherwise wiping out and bagging leaf litter means killing the animals sheltering within those leaves. Some of those leaves and animals can help your yard. Others can help garden areas.

When hibernating insects are mistakenly brought indoors for misguided safe keeping, they enter a warm environment that confuses their cycles, prompting an early emergence when the temperatures are too cold to survive outside and no food sources or mates are available. People might be concerned that some insect pests remain in the debris mix — so will many more predatory insects, spiders, and other beneficial organisms that keep the unwanted bugs at bay. Saving dried, hollow stems offers homes to mason bees — a way to help pollinators without using blossoms. Added bonuses to leaving leaves are:

  • Less yard work (or the expense of paying someone to do it)
  • Saved stalks and twigs hold the leaves in place, preventing them from blowing about
  • When plant matter eventually decomposes, it provides the best compost — far better than wood-based mulch

If you live in one of Fairfax County’s older neighborhoods and have too many leaves to leave on your grassy areas, consider leaving the leaves in the garden and flower beds and using your lawn mower on its highest setting to mulch the ones on the lawn. This feeds the lawn with a natural fertilizer. Michigan State research found an overall reduction in dandelions and crabgrass over time because leaf mulch covered any voids in the turf where the weeds would germinate in the future. This practice may allow homeowners to reduce their herbicide and fertilizer use.

Skipping synthetic yard chemicals is healthier for wildlife and soil microbes. Some plants need trimming, such as low-hanging branches and vegetation flopping across sidewalks. Consider scattering those bits around a garden, adding them to your compost pile, or lastly, sending them off for recycling. Never dump yard debris in natural areas, including parkland. Healthy land stewardship is easy, helps gardens, and encourages butterflies and other beautiful creatures to flourish next year.

Author Greg Sykes is an Invasive Management Area leader for the Fairfax County Park Authority.

References:

Jewell, Susan. 2009. That pesky yard waste: it’s biodegradable, so why can’t I just dump it in the woods? The Fairfax Chronicle 7(2):4. Reprinted with permission at http://www.grsykes.com/pdf/jewell-yard_waste.pdf.

https://xerces.org/blog/leave-the-leaves

https://www.nwf.org/Magazines/National-Wildlife/2015/OctNov/Gardening/Leave-the-Leaves

https://piedmontmastergardeners.org/leave-the-leaves

https://canr.msu.edu/uploads/files/Mulch_fallen_leaves.pdf