Have you noticed how yellow parts of Toronto look in the fall? While idealized images of fall foliage often comprise a variety of colours including oranges and reds, the city's tree canopy is slowly but surely losing some of this variety.

While fall is looking like it'll be beautiful in the Toronto area this year, our ravines are steadily being defined by the invasive Norway Maple, which tends to show only yellow when its leaves turn.

The most spectacular fall displays come from Sugar Maples, which are native to Toronto, but this tree is slowly being pushed out over time. The culprit is the Norway Maple, which was widely planted in Toronto in the early 20th century, but now poses a threat not just to fall colours but also biodiversity.

The tree is notorious for its shady canopy-covering tendencies, reducing sunlight for other species beneath it. Its shallow roots also worsen erosion in our ravines and prevent grass and other small plants from growing around it.

The City of Toronto recommends against planting the Norway Maple, as it is now considered an invasive species, but much of the damage is already done when it comes to the breadth of our fall foliage. While Norway Maples change colour later, they're just not as saturated.

While you can still expect a beautiful fall this year, if you're looking for the most colourful displays of foliage, you'll want to leave the city for areas where the concentration of Sugar Maples is higher.

Fortunately, we have many, many options.