It’s at about this time of year when the leave of our deciduous trees are starting to change colour and fall to the ground. Have you ever wondered what is happening to the leaves when they change colour and what you should do with them (i.e. leave them on the ground, compost them, gather them for municipal pickup?) We’ll cover all of that in this week’s tip.
As the days get shorter and the temperatures start to decline, this triggers a change in many deciduous trees. The tree is getting ready for the cold of winter and the shorter days, and the chlorophyll starts to disappear from the leaves. This leaves behind other colours like yellow, orange, and brown. A hormone is sent to the tree leaf stem, which separates the leaf from the tree (with the help of a little breeze). Red colours are triggered by the breakdown of sugars in bright light within the leaves.
Once the leaves fall to the ground, the next step is to decide what to do with the leaves. Before you do anything else, one thing we strongly recommend you chop or shred up the leaves by running your lawn mower over them several times. Ask a friend/neighbour to borrow theirs for a few hours if you don’t have one yourself.
If you don’t do any season extension or cover cropping, you can leave a layer of leaves directly on the garden. This will help to insulate the soil, minimize erosion, and reduce potential weed growth. The leaves will start to break down and feed the soil over the winter and in the early spring. If your layer of leaves is very thick, you can rake it back when you go to plant your spring crops.
Layering leaves in the garden can also be done throughout the growing season. This works best around more mature and taller plants as small/young plants can be smothered by too thick of a covering of leaves.
Next, we recommend storing extra leaves to use during next year’s garden season. You’ll use these shredded leaves in your composter, worm bin, and as mulch around your plants. If you don’t have many extra leaves from option 1, check your neighbourhood for those who may leave their leaf bags for the municipal pickup and shred and store those instead. Many gardeners can’t get enough shredded leaves and find it’s all gone sooner than they expect. Keep these stored leaves in a sheltered/dry place if possible.
If your compost is full, if you have the space, if you have enough leaves stored away for next year’s season, you can start the composting process by putting the leaves in a plastic bag with some water, a scoop of garden soil, and a few holes for drainage. They’ll start to decompose over the winter and depending on conditions, you’ll have some good leaf mold compost to use at the start of next year’s season.
If you can’t store the leaves, the last option we will recommend is to leave it out for municipal pickup. You can also post on online message boards like Craigslist or Kijiji for gardeners who may want to come and pickup your leaves for their garden if you don’t want this going directly to the city’s composting program.
Leaves are an excellent source of carbon that can help to stimulate/feed soil microorganisms, add organic matter to the soil and improve the quality of your plants and garden. Despite looking brown/dry, fall leaves contain lots of nutrition for the soil and their microorganisms such as worms, bacteria, fungi, and protozoa. Think of them as another crop you can harvest in the fall – an endlessly renewable resource that nearby trees provide to your garden.