Oct 182019

Still lots to look forward to in the parade of fall colours

From May’s gentle pastels and summer’s kaleidoscope of greens to early fall’s dazzling reds and oranges, each time of year has its signature colours. Now, as we move into the second half of October, yellow is taking over centre stage.

Once the red and sugar maples have shed their leaves, the main show belongs to the aspens, poplars, birch, tamaracks, and oaks. Only a matter of days ago, most of these species were simply part of the green blur, but they’ll soon stand out like yellow beacons on the landscape.

The trembling aspen is the most widely distributed tree in North America and one of my favourite species. The round, heart‑shaped leaves change from lime green in spring, to emerald in summer, and finally to lemon-yellow in fall. Not only are the leaves beautiful to look at, but they also produce their own soothing music. Their flattened leaf stem allows them to quiver at the slightest breeze, hence the name “trembling”. Why the aspen has evolved such flexible leaves is still a matter of speculation, but it may be to help protect the tree from strong winds by all allowing the wind’s energy to pass through the canopy more or less uninterrupted.

Although somewhat less common, the bigtooth aspen is an equally attractive tree. The leaves are larger than those of trembling aspen, with curved teeth on the margins. While most of the leaves do become bright yellow in the fall, some acquire rich shades of orange.

Balsam poplar, a tree of moist, low-lying habitats, also turns various hues of yellow in October. Almost as widespread as trembling aspen, balsam poplar has resinous, fragrant buds that perfume the spring air. It is the smell of May in the Kawarthas. The buds also possess medicinal qualities and exude a resin that is used to make balm of Gilead. Besides smelling wonderful, the balm is said to have anti-inflammatory and analgesic qualities.

By month’s end, tamaracks reach their colour zenith. Lime-green in early spring and smoky gold by late October, tamaracks are one of our most beautiful and interesting trees. They are the only conifer to lose all its needles in the fall. As the great American conservationist, Aldo Leopold, wrote so eloquently, the ground becomes “dusted with tamarack gold.” Our other conifers, such as pines and cedars, shed only a portion of their leaves each autumn. That is why some of their foliage becomes yellow or orange at this time of year before falling.

Preparation for winter

Colour change and the shedding of leaves are manifestations of a tree’s preparation for winter. It is a coordinated undertaking on the part of the entire organism. Since winter is a time of drought in which water is locked up in the form of ice, trees are no longer able to absorb water through their roots. Because leaves are continually releasing water vapour – think of the high humidity of a greenhouse – trees must get rid of their leaves in order to minimize water loss and avoid death through desiccation.

However, leaves are full of important, but scarce minerals, and it is to the tree’s advantage to salvage these nutrients first. These same minerals are used to produce chlorophyll, the green pigment that captures the sun’s energy and uses it in combination with water and carbon dioxide to produce the sugar‑based substances that make up all of the tree’s tissues – wood, bark, leaves, flowers, and fruit. As the amount of daylight decreases in late summer and fall, trees stop producing chlorophyll and begin to remove the minerals from the leaves in order to store them in the woody tissues until next spring. This same response occurs in times of drought.

As the chlorophyll disappears, colour change becomes apparent. Without green chlorophyll to mask the other colour pigments in the leaves – most of which have been there all along ‑ these pigments gradually become visible. The yellows and oranges come from carotene pigments, while anthocyanins give us the beautiful reds. The red pigments are created from excess sugars and seem to be brightest when there is lots of fall sunshine accompanied by cool nights such as this year.

The actual shedding of the leaves is achieved by the formation of a corky layer of cells at the base of each leaf stalk. Eventually, the leaf’s connection with the twig is broken, and it falls off in the wind, rain or simply from the warming effect of the morning sun. You have probably noticed how squirrel nests, made up largely of leaf‑bearing twigs nipped off the tree during spring and summer, will hold the leaves for years at a time. This is because the cork layer never had the time to form.

The story of October’s yellows would not be complete without mentioning our non-native trees. Norway maple, a species native to Eurasia, has become one of our most common urban trees. Its purple-leaved cultivar is especially popular. Of all the maples, the Norway is the last to change colour. The trees remain green until mid- to late October, before turning various shades of yellow. Some trees usually still have leaves on Remembrance Day.

In late October through early November, you get a real sense of just how ubiquitous Norway maples are. Along with other non-native trees like weeping willow and European buckthorn, they stand out conspicuously at a time when most native trees and shrubs have lost their leaves. To me, these trees stick out like soar thumbs in late fall and, not really belonging here, take away from our sense of place.

By November, the only native deciduous trees that still retain leaves are the oaks and some silver maples. Red oaks, usually dressed in brownish-orange leaves, stand out in particular. This makes it easy to see how common oaks are in many areas, especially on the Canadian Shield. Some oaks, along with young American beech, sugar maple, and ironwood (hop-hornbeam) retain a portion of their leaves all winter.

Seed and fruit

In addition to the colour parade of the fall leaves, there’s another interesting phenomenon happening this year. Anyone paying attention to our trees, shrubs and vines has no doubt noticed the abundance of seed, be it in the form of fruits, berries, nuts, or cones. Especially noticeable is the seed crop on sugar maples, American beech, mountain-ash, apple trees, white spruce, and wild grape.

Not surprisingly, the amount of seed produced in a given year is an adaptation to assure that the plant’s genes are successfully transferred to a new generation. We may not think of trees as having survival strategies, but millions of years of evolution have fine-tuned plants as much as animals to survive in a rough and tumble world.

In the boom or bust cycle of seed production, the prodigious quantities that we see some years is known as masting. The exact mechanisms are still unclear, but some researchers believe that trees may have biological clocks that are somehow synchronized and pre-programmed to mast at opportune times. It may also be that environmental cues such as wide-ranging climate conditions trigger the masting phenomenon.

Masting may also be a clever adaptation for survival. Let’s look at the example of oaks.  For several years in a row, oaks will produce no or very few acorns. This has the effect of greatly reducing the number of acorn-eating herbivores because, with little or no acorns, many will die, leave the area, or simply have fewer young. Then, with the herbivore population knocked down a few notches, something amazing happens: the trees suddenly produce a giant acorn crop. Those herbivores that are still around quickly become satiated and can eat no more. In this way, a significant number of acorns – or, depending on the species of tree, any other type of seed – will survive to grow into seedlings.

Masting has important ecological effects, too, as the food chain becomes distorted by so much food available. For example, the abundance of seeds resulting from a masting year in conifers allows seed-eating birds such as crossbills to lay more eggs than usual and to raise more young. However, in a low seed year following masting, the larger than usual number of seed-eating birds must migrate elsewhere to avoid starving.

As for this year, the abundance of wild grape will almost certainly mean that large numbers of robins will spend the winter in the Kawarthas. This is what happened just two years ago. Why migrate further south when all the food you need is here?

What’s happening this week

Golden eagles migrate south through the Kawarthas from mid-October to early November, along with large numbers of red-shouldered and red-tailed hawks. These raptors are best seen from a height of land where a large swath of sky is visible. Last year, a group of us saw several golden eagles and numerous hawks from a ridge just east of Petroglyph Provincial Park.

Climate Crisis News 

As we head to the polls on Monday, let’s remember the importance of keeping the climate crisis front and centre in our minds. A recent article in Maclean’s by Canadian climate scientist, Kathyrn Hayhoe, and economist, Andrew Leach, graded each party’s climate plan. They give the Liberal’s plan a B for ambition and an A for feasibility; the NDP’s plan an A for ambition and a D for feasibility; the Green’s plan an A+ for ambition and a C- for feasibility; and the Conservative’s plan a D for ambition and a F for feasibility. The high marks given by experts to the Liberal plan have made my decision much easier.


Sep 242017

Now’s the time to take in the beauty of autumn at Ontario Parks!

The 2017 Ontario Parks Fall Colour Report is LIVE! Check for the latest colour changes in up to 60 provincial parks across Ontario by using the report’s map and peak-viewing chart. Staff will be updating their park reports every week so check back often for the latest conditions. Climatologists predict brilliant reds and golds, thanks to an abundance of rain.

Mid-September to late October is prime-time viewing when campsites are plentiful and camp cabins and yurts are easier to book.

Algonquin Provincial Park is extremely popular on peak fall colour weekends. Before you visit Algonquin, this is what you need to know.

The Parks Blog also suggests other fall colour parks worth visiting. In Northern Ontario, try these parks. More park choices are found in this fall colour post.

Lots of special events are also planned. Visit the Ontario Parks’ calendar of events for details.

Ontario Parks posts regularly on Twitter and Facebook.

High-resolution, credited photography related to the above can be downloaded from a mini photo library here.

We’ll see you there!

Sarah McMichael

Leaf colour east of Apsley – October 1, 2012

Oct 132016

In October, our attention is drawn to leaves like at no other time of year. They never cease to astound us with their blazing colours and wonderful, spicy smell as we rake them into piles. For the rest of the year, however, we mostly take leaves for granted. They just seem to “be there” doing nothing. But, like everything in nature, leaves are far more amazing than what initially meets the eye. Nothing about them is arbitrary or purposeless.

The characteristics of leaves only make sense when considered through the lens of evolution by natural selection – the process that favors the survival and reproduction of individuals that are best adapted to their environment. So, let’s consider leaves the way Charles Darwin would: By asking “why” questions. Let’s begin by exploring why trees have leaves in the first place. Simply put, leaves make food for the plant – be it a towering white pine or a lowly moss – so that it can grow. This happens through photosynthesis. “Photo” is the Greek word for “light,” and “synthesis” means “putting together.” That’s exactly what is happening. Leaves harness the energy of sunlight to make food in the form of sugars like glucose. Some of the glucose is immediately used for growth (e.g., the production of cellulose and lignin which makes up wood) while the rest is stored for later. Glucose is produced from two ingredients: carbon dioxide and water. Plants breathe in the carbon dioxide, an invisible gas, through tiny holes in the leaves. They use their roots to suck up water. Some of the water is released back into the atmosphere through the leaves by transpiration. At the same time as glucose is produced, oxygen is released as a waste product. Not only is photosynthesis responsible for the production and maintenance of most of the Earth’s oxygen, but it provides the organic compounds necessary for life on Earth. No small feat!

Sugar Maples - Cy Monkman

Sugar Maples – Cy Monkman

Photosynthesis is directly related to another why question: why are leaves green? Leaf cells house tiny structures called chloroplasts. Each chloroplast contains a green pigment (chemical) called chlorophyll, which absorbs the sun’s energy and carries out photosynthesis. As long as chlorophyll is present, the leaf remains green and oxygen and glucose are produced.

Colour change

This begs the question of why leaves change colour and why they are shed from the tree. Both of these phenomena are manifestations of the tree’s preparation for winter.  It is a coordinated undertaking on the part of the entire organism.  Since winter is a time of drought in which water is locked up in the form of ice, trees are less able to take up water through their roots – most of which are near the surface in soil that freezes.  In addition, leaves are continually releasing water vapour through transpiration – think of the high humidity of a greenhouse. Trees must therefore get rid of their leaves in order to minimize water loss and death through desiccation. Also, the leaves of most trees are far too delicate to withstand the rigours of winter.

Before shedding their leaves, however, trees have evolved to salvage the scarce but valuable minerals or nutrients in the leaves. These were originally obtained from the soil through the roots. They include magnesium (an essential component of chlorophyll), calcium, phosphorus, potassium and nitrogen, which is part of all proteins. Given their relative scarcity, a tree can’t afford to lose most of these nutrients each fall when the leaves are shed. It wouldn’t be able to reabsorb them in time or in sufficient quantity to be available for the next generation of leaves. Therefore, as daylight begins decreasing in mid-July, trees start removing these nutrients from their leaves and storing them in the woody tissues until next spring. By sometime in September, the leaves can no longer manufacture chlorophyll and begin to lose their green coloration. At this point, other pigments like the yellows and orange carotenoids gradually become visible. These pigments were present in the leaves all along but were masked by the chlorophyll.

A group of red or purple pigments known as anthocyanins are also abundant in some leaves like those of white ash and both red and sugar maples. They are produced in late summer from excess sugars and are brightest in years with lots of sunny days and cool nights. Scientists are not yet certain about the role of anthocyanins but they may protect the leaves from ultraviolet light.

Leaves of red maple changing colour - Photo by Drew Monkman

Leaves of red maple changing colour – Photo by Drew Monkman

The actual shedding of the leaves is achieved by the formation of a cork-like “abscission” layer of cells at the base of each petiole (leaf stem). Eventually, the leaf’s connection with the twig is broken, and it falls off in the wind, rain or simply from the warming effect of the morning sun.  You have probably noticed how squirrel nests, made up largely of leaf‑bearing twigs nipped off the tree during spring and summer, will hold their leaves for years at a time. This is because the cork layer never had the time to form so the leaves remain attached.

Other stories

Leaves have many other why questions to answer and stories to tell. To think like Darwin, let’s consider other challenges a leaf faces. These include being eaten, over-heating, drying out, being blown off the twig, receiving enough sunlight – to name a few.

You may, for example, wonder why so many different shapes and sizes have evolved. Scientists have discovered that toothed or lobed leaf margins (e.g., toothed in elms, lobed in oaks) are an adaptation that allow leaves to more quickly rid themselves of absorbed heat. If heat release is not a problem, as with plants like hostas that grow in shady habitats, the margins are “entire”, which means they are even and smooth all the way around. Almost all leaves, however, come to a sharp point – often at the tip – which is an adaptation to shedding water.

Darwin no doubt wondered why some leaves are “simple” like those of a maple or compound like those of a sumac or walnut. To tell if a leaf is compound, look at where the petiole (leaf stem) is attached to the twig (usually a different colour and woody). You should be able to see a bud. A simple leaf has a petiole and one blade. A compound leaf has an elongated petiole with three or more leaflets (blades) coming off it. Each leaflet looks like a separate leaf, but there is no bud at the base of the leaflet’s stem (petiolule) – only where the main petiole is attached to the twig.

Why would natural selection sometimes favour compound leaves? First, they provide lots of surface area for photosynthesis – sumacs can have 31 leaflets – but still allow wind and rain to largely pass through them. Imagine what would happen to a huge simple leaf in a storm! In addition, compound leaves don’t heat up so much because air circulates around the leaflets. These advantages may explain why compound leaves are so common in the tropics.

Compound leaf of ash (left) and simple leaf of sugar maple Note tiny bud where stem meets the twig - Photo by Drew Monkman

Compound leaf of ash (left) and simple leaf of sugar maple Note tiny bud where stem meets the twig – Photo by Drew Monkman

The overall size of leaves is not a matter of chance, either. Leaves tend to be largest on plants that grow in shaded areas – think of the size of Hosta leaves – and on the lower, more shaded branches of trees such as oaks. Leaves at the top of a tree tend to smaller. Larger leaves, of course, gather more light.

Leaf thickness, texture and hairiness are also interesting. Hairs and even spines on leaves have evolved to make them less appetizing to herbivores like caterpillars and deer. Hairs can also protect delicate growing parts from the cold. You often see them on early-spring species like hepatica and arugula. Thick and waxy leaves – think of conifer needles and the leaves of English holly – suffer less water loss, which means the tree doesn’t need to shed them in the winter. They are also common in hot, dry environments.

Take time to smell leaves and to ponder the question of why some leaves are so aromatic. Although certain leaves might smell good to us – wintergreen and bergamot, for example – it’s quite likely that the chemical compounds responsible for the smell are poisonous or taste bad to leaf-munching herbivores!

Leaf collection

Why not take some time this fall to really get to know the leaves of our common broad-leaved trees? One way is to make a collection, either by yourself or with your children, grandchildren or students. Place the leaves between sheets of newspaper with heavy books on top. Leave for a week or so. When the leaves have dried out, you may wish to place them between two sheets of clear, adhesive contact paper for greater protection. Using one or two sheets of Bristol board, group the leaves by colour, by genus (e.g., all the maples together) or by simple and compound. A basic collection for the Kawarthas would include simple leaves like sugar maple, red maple, silver maple, red oak, white birch, American elm, trembling aspen, American basswood, chokecherry and willow. As for compound leaves, try to find white or green ash, staghorn sumac, Manitoba maple, black walnut, Virginia creeper and black or honey locust.

Fall is a wonderful time to explore and celebrate nature, especially through the lens of why questions. Nothing in this Universe is more magical or awe-inspiring than reality!

Nov 062014

We don’t often think of November as a particularly interesting month. For many, it’s simply the grey, damp interval between the dazzling leaves of October and the swirl of lights and decorations of December. For me, however, late fall has always been a favourite time of year. I love the change of pace and the sense of nature slowing down. Most migratory birds have departed and insect activity has been reduced to a few hardy moths and dragonflies. Gone are the dramatic day-to-day changes in leaf colour that enlivened the landscape just a few short weeks ago. With the veil of foliage now lifted, what stands out are nature’s fundamentals – sky, water, soil, rock and tree

Common Raven - Wikimedia

Common Raven – Wikimedia

With these November thoughts in mind, I took advantage of last Sunday’s beautiful weather to go for a long walk. And what better place to explore the outdoors than the Shield country of Big Gull Lake, where my wife and I were spending the weekend. It’s such a pleasure at this time of year to walk freely, unencumbered by summer’s heat and insects or winter’s snow and ice. The cool, invigorating air infuses your every step with new-found energy. But rather than focus on exercise or species’ identification, I decided to concentrate on walking mindfully and being fully aware of the simple pleasures of sight, sound and smell.

Other than the rhythm of my own footsteps on the dirt road, I was surrounded by what seemed like total silence. There was no rattle or buzz of insects and no singing birds. Man-made sounds, too, were absent. No chain saws, no ATVs, and no outboard motors. But I soon realized that this November day did indeed have a voice; its voice was the wind. And it wasn’t one wind but many: the roar of high-altitude gusts that sent clouds scurrying across the sky, the murmur of softer breezes in the pine boughs overhead and especially the constant crackle and rustle of air rushing through the dry leaves. About the only other sounds that came my way were the croaking of a distant raven, the explosion of wings of a startled Ruffed Grouse and the loud scolding of a disgruntled Red Squirrel.

Oaks are among the last trees to lose their leaves in fall - Drew Monkman

Oaks are among the last trees to lose their leaves in fall – Drew Monkman

As much as I love the soundscape of the natural world, I also take pleasure in the absence of sound. The stillness of late fall somehow makes us more aware of the ancient rhythms of the land as nature settles down for winter. How rare it is anymore to ever enjoy real quiet, removed from the cacophony of man-made noise to which we’ve become so fully habituated. As Sigurd Olson, an American writer and conservationist once said: “In the end we turn to nature in a frenzied chaotic world to find silence, oneness, wholeness, and spiritual release.”

On such a spectacular sunny day, I couldn’t help but notice the special quality of the light. November light is different. It is not the harsh, mid-day glare of summer that blazes down upon us from straight above. November light comes to us aslant, casting long shadows in its course. A quick glance at the sun explains why. Even at noon, the late-fall sun is little more than half way between the horizon and the sky’s zenith.

 Cottage road in November. Note the long shadows, even at noon - D. Monkman

Cottage road in November. Note the long shadows, even at noon – D. Monkman

Even though I’ve walked this road countless times, late fall always surprises me with new vistas and natural features I’ve never noticed before. With most of the leaves now fallen, the outline of distant hills and valleys seemed somehow different. Even the roadside woods appeared bigger and invited exploration. Where only recently there was a curtain of greenery, I could now make out granite ridges, scattered erratics (huge stones left behind by the glaciers), newly fallen trees and even some woodland ponds that I’d never seen before. But more than anything, the forest interior was mostly a play of dark tree trunks, long shadows and fallen leaves. What really caught my attention, however, was how the angled November sunshine magnified the oak leaves’ natural glaze and made them sparkle like diamonds. Even the individual leaves on the road’s surface blazed like tiny flares.
Scattered about the forest floor, I also noticed numerous oases of greenery. Some were patches of green moss on a rock or log, but there were also clumps of evergreen ferns like Wood Fern and Rock Polypody, club-mosses such as Ground-pine and Ground-cedar, and evergreen wildflowers like Hepatica and Wintergreen. It was almost as if these plants were saying: “We don’t want anything to do with this change of season!”

True to its name, Wintergreen stays green all winter - Drew Monkman

True to its name, Wintergreen stays green all winter – Drew Monkman

I was also reminded of just how common oaks are in the Kaladar area. Since most of the oaks still retained some of their leaves, they stood out clearly against the other deciduous trees, most of which were bare. Conifers, too, were more conspicuous than usual. Looking towards the horizon, I could see numerous White Pines towering above the other trees and clearly displaying their iconic wing-like branches. Along the edges of wetlands, spire-shaped Balsam Firs, columnar White Spruce and smoky-gold Tamaracks were all easy to spot.
The roadside, too, provided items of interest, including a few remnants of fall colour. A small display of pinks, reds and burgundies came courtesy of the remaining leaves on the Maple-leaved Viburnums, Common Blackberries and the seedlings of Red Oak. I also noticed a handful of asters still clinging to their mauve petals. Much more common, though, was the huge variety of seeds such as those of the milkweed spilling from half-open pods and the fluffy grey seed heads of the goldenrods. The promise of spring wasn’t hard to find, either. The numerous young maples and cherries growing along the edge of the road were covered with fully-formed buds, just waiting for April rains and warmth to swell and open.


In much the same way as November is not a time of sounds, nor is it a time of smells. The cool temperatures of this particular morning had even neutralized the lovely fragrance of the fallen leaves. As I returned to the cottage, however, the faint smell of wood smoke immediately caught my attention and had me looking forward to the warmth of the fire and a cup of coffee.
When we arrived back in Peterborough in late afternoon, it was already getting dark. With the return to Standard time, dusk comes early at this time of year. But short days, too, are something I love. In my mind’s eye, I see the northern hemisphere tilted sharply away from the sun. I imagine the sun’s rays striking our part of the world diagonally, scattering themselves over a much larger area than in summer and creating far less warming. Short, cool and reduced to nature’s fundamentals, these November days are no less than a palpable reminder of the change of season – and seasonal change is what makes living in the Kawarthas so wonderful.

The smell of a woodstove

The smell of a woodstove