This is a time of year when plenty are finishing the Fall clean-up by pruning back roses, cut dry stems of spent flowers, cleaning gutters and yes: raking leaves. Leaf blowers, rakes are pulled out, hours are spent making piles and most of the time, those piles are carried to the street to be picked up by the municipality Public Works.
Have you ever thought of not raking your leaves and see what happens during the Winter? If you pay attention, the leaves will quickly start their process of decomposition and inevitably break down to be pulled into the ground by worms and insects that count on that litter for food and shelter. Even the leaves left on lawn will disappear – even faster if you run your mower over them to be shredded.
Urban landscapes are very often sterilized by the application of synthetic fertilizers and other pesticides designed to help the plants and trees. In reality, that need to make the landscape “look good” leads to an erroneous idea of health. The lawn is green and lush, the plants and trees seem to grow and survive but the soil, the principal foundation of health for anything that grows is mostly sterile. The synthetic fertilizers are the equivalent of food given to a starving organism while the environment around is bleak and lifeless. By pushing the imagination, a plant like a rhododendron for example could survive in a container of sand so long as a regular injection of food (fertilizer) is applied with water. There is hardly anything organic in the sand but by providing the necessary food and water, the plant survives… but it doesn’t thrive.
In comparison, undisturbed soils like the ones seen in forests are extremely alive. Years of litter left to decompose create an amazing environment for the insects, worms, fungi and a vast microbiology that transform the litter into nutrients that will be taken in by the feeder roots of the trees and plants.
Another important aspect of the soil seen in the forest is its porosity. A constant composting is happening right under our feet by all the organisms responsible for breaking down the organic litter so a humus is created allowing the water to penetrate easily, oxygen to keep the soil “alive” and feeder roots to travel easily in search of nutrients.
I have purposefully kept all my leaves over the years I have lived in my place (since 97) and have seen an amazing transformation over time. The soil has become richer, water penetration is almost instantaneous and my trees and plants are thriving, also being able to cope with the increasing dry summers we have witnessed. If exposed to Aphids or another common pest, they seem to bounce better and faster by having grown in a healthy soil. My consumption of fertilizer is non-existent and so is the application of pesticide.
Soils become compacted easily even by simple foot traffic, especially if the cushy leaf litter is systematically removed. The common reaction is to add bark-o-mulch to cover the soil when the leaves are removed but even if the layer of mulch provides some protection from compaction, it is very poor in nutrients. Some of us live in neighborhoods regulated by Home Owner Association rules that are usually much less tolerant of leaves left on lawns. Just let the lawnmower bag the leaves and they will be automatically shredded then all you have to do is spread the content in the flower beds or around the base of your trees (without piling against the trunk). Heck, you can even cover it with bark-o-mulch if it needs to look very clean and up to the HOA Standards.
Finally, if the soil is really compacted and the plants and trees seem to suffer from it, there is a way to help via a process called verti-mulching which is the incorporation of compost or organic matter into the soil by drilling holes with a small auger then filling the holes. If the compost has been spread on the ground prior to the drilling, it will be incorporated as the holes are being drilled. That operation has a two-prong advantage: inoculating poor soil with organic matter and aerating the ground. Slowly, the microbiology of the organic matter will colonize the soil and slowly improve it over time.
The auger can be invasive and such an operation should require locating for utilities so another way to help without running the risk of hitting roots or utilities is using a pneumatic “air knife” called Airspade®. Imagine an air wand connected to a compressor that will blast air through a 1” wide opening. The tip is inserted in the ground and the air fractures the compacted particles of the soil to allow more oxygen to penetrate. If, like with the verti-mulching, compost has been spread on the surface, it will be pushed down and spread below grade even easier therefore accelerating the recovery of your soil. Our company owns an Airspade® which we have used in numerous occasions to improve soil compaction with amazing results.
In short, restoring a healthy environment for your plants and trees is an easy start. You have the right to a “lazy streak” and leave the leaves where they lay but if you really feel like raking, rake them into your flower beds, you’ll be surprised by the results. You should remove them from the sidewalk and street gutter at least to avoid tripping and slipping risks and allow proper drainage along the street.
Alby Thoumsin
ISA Certified Arborist, PN 1168A
ASCA Registered Consulting Arborist #452
