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Fall Colours in October

Autumn colours are on display in Wilket Creek ravine, the vibrant reds and oranges from the iconic native sugar maple (Acer saccharum) and red maple (Acer rubrum). Colours are due to the yellow-orange carotenoid and red anthocyanin pigments which appear in the leaves, as the green pigment chlorophyll breaks down.

With invasive non-native Norway maple (Acer platanoides) invading natural areas and displacing native trees, we risk losing this iconic fall foliage of our forests. Norway maples do not produce the same vibrant colours as our native maples, instead turning brown or yellow, and often covered in unsightly black tar spots. Norway maples in Wilket Creek ravine, along with other ravines in Toronto, originate from escaped landscape plantings. They negatively impact our forest ecosystems by providing poor habitat for native insects, which in turn means fewer birds foraging on their branches. Norway maples also inhibit ground flora and native tree regeneration.

Here are some ways to differentiate invasive Norway maple from native sugar maple:
Leaf – Norway maple leaves are wider and have more lobes (5-7), compared to sugar maple with fewer lobes (5). Norway maple also often has numerous tar spots on its leaves, while sugar maple is less affected.
Sap – Norway maple emits a milky white sap from the stem, while sugar maple sap is clear.
Bark – Norway maple bark is smooth and vertically striped when young, but with shallow grooves when mature often in a diamond pattern. In comparison, sugar maple tends to be rougher and with vertical ridges that often curl outward.
Fall Colour – Norway maple typically turns brown or yellow, while sugar maple turns orange to red.

When summer wanes, few plants are as vibrant as asters, colouring the landscape in an array of purples, blues, and whites. Typically flowering late summer and fall, native asters are an important late nectar and pollen source for insects, and their seeds an important food source for birds. There are ~30 asters native to Ontario, the largest and most common group being the American asters (Symphyotrichum sp.). Pictured here are asters observed during flora surveys in Wilket Creek ravine, showing just a fraction of the wide variety in our native asters. Native asters range from woodland, grassland, to wetland species, and vary in colour from white to sky blue, and pink to deep purple.

Pictured here are native asters:

New England aster (Symphyotrichum novae-angliae)‎

Swamp aster (Symphyotrichum puniceum)‎

Calico aster (Symphyotrichum lateriflorum)

Panicled Aster‎ (Symphyotrichum lanceolatum)

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