The leaves have had their moment of glory in the sun. Most have fluttered to the ground where they lie resplendent, turning ordinary pathways into a yellow-brick road. As autumn fades, fallen leaves become a burden, clogging gutters and smothering lawns. But for gardeners, deciduous leaves are a tremendous resource.
Before I explain how to use your leaves, I need to say a few words about evergreens. Homeowners have been alarmed by the large number of yellow needles they have noticed on spruce and pine. Evergreen needles do not stay green forever. Trees shed the oldest needles near their center. In years when there’s been a droughty spring, this phenomenon is especially noticeable in autumn.
I have never seen so many drought-curled leaves on deciduous trees and shrubs as I have this past September. But drought isn’t the reason birch, aspen and willow leaves started dropping prematurely. The cause was likely a lack of chlorophyll from leaf miner feeding. The question is where are those leaf miners now?
Aspen leaf miners and willow leafblotch miners are not in the leaves. The adult moths overwinter in the cracks and crevasses of tree bark. On birch, there are two species of leaf miners responsible for the large, brown leaf blotches. These insects are sawflies, not moths. The amber-marked birch leaf miner larvae dropped out of the leaf tissue before the leaves fell and will overwinter on the ground in a prepupal resting stage. Not so for the late birch leaf edge miner. They fall to the ground inside the leaves, where they’ll spend the winter as pupae.
Given Interior Alaska’s huge populations of birch leaf miners these past years, there’s no need to be worried about using the leaves. The adults will just fly in from around the neighborhood to lay eggs in or on the leaves of your trees next summer. According to Stephen Burr, forest entomologist with the USDA Forest Service in Fairbanks, tree mortality has not been observed as a result of birch leaf miner defoliation.
Remove the leaves from your gutters to prevent ice from damming up this winter, but there’s no need to rake the leaves off your lawn. Recycle fallen leaves by chopping them to small bits with the lawn mower. An extra pass or two may be required but using the mower is easier than raking. As a kid, I considered raking an onerous chore, but only until the pile of leaves was large enough to jump into. How those scattered leaves ended up in bags, I’m not sure but bagged leaves are the gardener’s friend.
Leaves can be used to protect temperamental perennial flowers. After the ground freezes, mound leaves loosely over the top of perennials making sure they are over a foot high. I don’t recommend overwintering perennials in containers but if you’re going gamble, hedge your bets by packing bags of leaves around all sides of the container. Without much effort, bagged leaves can also be turned into leaf mold, a fluffy organic summer mulch not available for purchase. The recipe is simple. Place leaves in bags and wait. Punch holes in the bag if you want decomposition to be aerobic.
The principles of composting apply to making leaf mold, the smaller the particle size, the faster the breakdown. If you want your leaf mold ready to use next summer, run the lawn mower through your pile of leaves before bagging. Leaves should not be bone-dry. The organisms that turn your leaves into black gold require moisture.
If you stockpile bags of dried leaves this fall, you’ll have a ready source of high-carbon material to add to those nitrogen-rich grass clippings you dump at the perimeter of the yard. Materials high in carbon are often short in supply during the summer months. Having dry leaves to add to the compost pile will help prevent the terrible smell that occurs when composting only fresh clippings and kitchen waste.
Before saving bags of leaves for next summer, I caution you to check for regulations on the accumulation of garbage. To the garbage police black bags of leaves appear as trash, not treasure. If your subdivision has garbage covenants, consider loading leaves into orange, smiley-faced pumpkin bags. It is the season to decorate for Halloween.
Julie Riley is horticulture agent for UAF Cooperative Extension Service in the Tanana District office and can be reached at firstname.lastname@example.org or 907-230-7339. To enjoy the season, she suggests attending the Fall Festival, where you’ll find real pumpkins in the Pumpkin Patch from 4-8 p.m., Oct. 4 at the Tanana Valley State Fairgrounds.