If we can convince Hamilton gardeners of one thing this fall it would be to keep and make better use of their fall leaves. In our “The Garden in Fall” workshop, we shared a number of reasons why keeping fall leaves in the yard is important.
First, the leaves are a free, insulating blanket for your plants. With the shifting weather, Hamilton has more snow free winter days. Snow actually provides good insulation for plants and without it, plants are exposed to not only more hard freezing events, but also dry winds that can dessicate plants. Leaving the leaves around plants protects roots and crowns against dry, cold winds.
Second, leaf litter is also an essential habitat for overwintering insects, amphibians, and mammals. Moths and butterflies in particular use leaf litter for overwintering in egg, caterpillar, and chrysalis stages. Luna moths, wooly bears, fritillaries, and hairstreaks are all examples of moths and butterflies that use leaf litter for overwintering.
Lastly, leaf litter when it breaks down provides wonderful compost and improves soil texture.
It’s common for gardeners to purchase straw to insulate plants and bulb plantings in the fall when leaves provide a free resource available widely and do not involve fossil fuels in order to harvest it.
We do acknowledge that for some yards, leaf litter can be abundant and the desire to keep leaves off of lawns is important to some gardeners. That’s where creating leaf mold bins comes in.
Leaf mold is simply composted autumn leaves. Unlike a garden compost pile, no other materials are mixed into the bins. The process for decomposition therefore is slower and cooler than garden compost and broken down more by fungal than bacterial action. Leaf mold is also a lower nutrient compost, but its real benefit is the fluffy, light texture it can add to soil and potting mix. It’s not commonly found as a component of potting mix but makes a terrific, more sustainable alternative to peat. Peat, harvested from peat moss bogs in Northern Canada, is common but because it forms so slowly, it is considered a non-renewable resource. Leaf mold would also be a better alternative when compared to coconut coir, which is commonly found in mixes now, but must be shipped from distant, tropical areas where coconuts are grown.
Making leaf mold is also very simple. All that’s needed is chicken wire or hardware cloth, wooden or metal posts, zip ties or string and the leaves. Taking the posts, you can set up the shape you desire. The posts can be pounded into the ground or the bin can be freestanding (perhaps depending on how windy where you plan to set up). The wire or cloth is then affixed to posts and the bin is ready to be filled. Unlike a garden composting system, the leaves do not need to be turned, so the bin does not need to be accessible. Leaves are piled in as much as the bin can hold and then left for a year to decompose slowly. The bin needs chicken wire or hardware cloth because there still needs to be airflow. The bin should also be in a place open to elements to get the leaves periodically wet. Because there is no decomposing food, the bin should not be very attractive to wildlife.
Bins can be set up in fall or spring. Leaves left in the garden to act as an insulating blanket can be raked up in spring and put into the bin if leaving them in the garden is not desired. However, it is important to leave leaves in the garden until nights consistently reach 10 degrees celsius, allowing overwintering insects to wake up and emerge. Remember to resist those warm March days for spring clean up!