Leaves are garden gold Wherever you live, your current address was probably a forested area 300 years ago. Trees grew and dropped their leaves in autumn and the leaves slowly composted on the forest floor, releasing nutrients into the soil. Tree roots absorbed these nutrients and used them to manufacture the next season of leaves. This cycle of growth and renewal can work in gardens where leaves are gathered and allowed to remain as a blanket over tree roots. Instead of cultivating grass lawn right up to tree trunks, consider removing grass from under tree canopies and allowing leaves to remain over the roots where they belong. Leaves can feed more than the trees from which they fall. Leaves contain all of the nutrients essential for plant life, including nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, zinc, iron and much more. Their fibrous content greatly enriches soil texture, enhancing adequate drainage and fertility. It’s not necessary to bother digging leaves into soil, although that is an admirable effort. Simply sweeping leaves onto garden beds, covering bare soil surrounding hedges, shrubs and perennial plants will reap long-term rewards. Soil fertility will be enriched, essential soil micro-organisms will increase, and the addition of leaf fibre will make nutrients more accessible to plant roots. A blanket of leaves over bare soil also helps to suppress weed growth, prevent excessive evaporation of soil moisture and maintain cooler temperatures in the root zone. Leaves don’t need to be chopped or shredded into small pieces to be useful. Birch, silver maple, English oak, locust, ginkgo, dogwood, crabapple and lilac leaves are small enough to be used for a blanketing mulch as soon as available. If the weather is dry and fallen leaves are crispy, running a lawn mower over them will easily chop them into small pieces, although this is unnecessary. (Fine pieces of shredded leaves are an excellent soil conditioner for lawns.) Large leaves such as Norway maple and full-size oak could benefit from a pass through the lawn mower, but they can be used whole in a thinner blanketing of approximately one- to two-inch depth. Be sure to include any coniferous needles available from pine, cedar and spruce – they are effective in opening pathways for oxygen to enter the soil. Contrary to common assumption, conifer needles will not contribute excessive acid to the soil environment. After laying down a two- to four-inch-thick mulch of leaves over bare soil, use a garden hose to thoroughly wet the leaf blanket (or let rain do the job). After drying, this initial shower will help leaves to remain in place and prevent them from blowing around. Although the mulch will appear quite thick and fluffy, at winter’s end, the leaf blanket will shrink down by about a third. If you have too many leaves for immediate use, sweep them into a pile someplace convenient, and let them rest there uncovered through winter. In spring, the leaf pile will have noticeably lowered, the leaves will be softened and partially degraded and you can use them as a source of soil enrichment when planting all through the following summer. Leaves left in an uncovered pile will require two winters to degrade into a luxurious form of leaf mulch, one of the most valuable additions to soil. Gardening CSANews | FALL 2023 | 45
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