Ontario's Fall Leaf Colour Change
The fall colour leaf changes highlight autumn in North America's central and northeast region with spectacular sight seeing opportunities. Ontario colours are outstanding in the detail of the many tree varieties (maples being predominant). The maple and oak trees morph into a painter's palette of gold, orange, red and yellow! On a sunny day, the colors are more vibrant, to be sure.
But even on a cloudy day, red maples and golden oak leaves bring a glow amidst the gray. Strong winds and rains will blow the leaves off the trees, so it's a delicate balance between seeing fall colors at their finest show, or a pile of colourful leaves on the ground. But even walking on that carpet of leaves is a special experience. The geographic scale where the colours seem to roll like waves over hundreds of thousands of hectares is a sight not to be missed. Getting a breathtaking colour high by standing on a hill with a scenic view, is a magnificent technicolour experience
Why Do Leaves Change Colour in the Fall?
Three factors influence autumn leaf color-
- leaf pigments,
- length of night
But the timing of color change and leaf fall are primarily regulated by the calendar, that is, the increasing length of night. None of the other environmental influences-temperature, rainfall, food supply, and so on -are as significant as the steadily increasing length of night during autumn. As days grow shorter, and nights grow longer and cooler, biochemical processes in the leaf begin to paint the landscape with Nature's autumn palette.
The photos in the Fall Colours photo album were submitted by our hiking community to illustrate the variety and intensity of colours in the fall Ontario landscape. Click icon below to view.
I'm trying out a newer photo album in the second icon below with the woodgrain theme. Any preferences?
Where do the Colours Come From?
A color palette needs pigments, and there are three types that are involved in autumn color.
- Chlorophyll, which gives leaves their basic green color. It is necessary for photosynthesis, which is the chemical reaction that enables plants to use sunlight to manufacture sugars for their food. Trees in the temperate zones store these sugars for their winter dormant period.
- Carotenoids, which produce yellow, orange, and brown colors in such things as corn, carrots, and daffodils, as well as rutabagas, buttercups, and bananas.
- Anthocyanins, which give color to such familiar things as cranberries, red apples, concord grapes, blueberries, cherries, strawberries, and plums. They are water soluble and appear in the watery liquid of leaf cells.
Both chlorophyll and carotenoids are present in the chloroplasts of leaf cells throughout the growing season. Most anthocyanins are produced in the autumn, in response to bright light and excess plant sugars within leaf cells.
During the growing season, chlorophyll is continually being produced and broken down and leaves appear green. As night lengthens in the autumn, chlorophyll production slows down and then stops and eventually all the chlorophyll is destroyed. The carotenoids and anthocyanins that are present in the leaf are then unmasked and show their colors.
Certain colors are characteristic of particular species. Oaks turn red, brown, or russet; hickories, golden bronze; aspen and yellow-poplar, golden yellow; dogwood, purplish red; beech, light tan; and sourwood and black tupelo, crimson. Maples differ species by species-red maple turns brilliant scarlet; sugar maple, orange-red; and black maple, glowing yellow. Leaves of some species such as the elms simply shrivel up and fall, exhibiting little color other than drab brown.
The timing of the color change also varies by species. Sourwood in southern forests can become vividly colorful in late summer while all other species are still vigorously green. Oaks put on their colors long after other species have already shed their leaves. These differences in timing among species seem to be genetically inherited, for a particular species at the same latitude will show the same coloration in the cool temperatures of high mountain elevations at about the same time as it does in warmer lowlands.
How does weather affect autumn color?
The amount and brilliance of the colors that develop in any particular autumn season are related to weather conditions that occur before and during the time the chlorophyll in the leaves is dwindling. Temperature and moisture are the main influences.
A succession of warm, sunny days and cool, crisp but not freezing nights seems to bring about the most spectacular color displays. During these days, lots of sugars are produced in the leaf but the cool nights and the gradual closing of veins going into the leaf prevent these sugars from moving out. These conditions-lots of sugar and lots of light-spur production of the brilliant anthocyanin pigments, which tint reds, purples, and crimson. Because carotenoids are always present in leaves, the yellow and gold colors remain fairly constant from year to year.
The amount of moisture in the soil also affects autumn colors. Like the weather, soil moisture varies greatly from year to year. The countless combinations of these two highly variable factors assure that no two autumns can be exactly alike. A late spring, or a severe summer drought, can delay the onset of fall color by a few weeks. A warm period during fall will also lower the intensity of autumn colors. A warm wet spring, favorable summer weather, and warm sunny fall days with cool nights should produce the most brilliant autumn colors.
What triggers leaf fall?
In early autumn, in response to the shortening days and declining intensity of sunlight, leaves begin the processes leading up to their fall. The veins that carry fluids into and out of the leaf gradually close off as a layer of cells forms at the base of each leaf. These clogged veins trap sugars in the leaf and promote production of anthocyanins. Once this separation layer is complete and the connecting tissues are sealed off, the leaf is ready to fall.
ONTARIO FALL COLOURS VIDEO: