Tag Archives: Norway Maple

The Invasive Threat of Norway Maples in Raymore Park

Norway maples (Acer platanoides) are everywhere in Raymore Park. They belong to one of many invasive species and will rapidly occupy land that isn’t mowed to the detriment of other plants and animals.

They were first introduced to North America in 1756 by John Bartram of Philadelphia, who imported the trees from England for sale as ornamental landscaping plants that quickly provided lots of shade. They have spread quickly since then by natural means as well as through human intervention.

Norway maples range in North America. https://nyis.info/species/norway-maple/

They were mass planted in Canada after the Second World War as a replacement for the magnificent elm trees which were dying out because of Dutch elm disease. Norway maples don’t just provide lots of shade, they are disease resistant and grow quickly while tolerating air pollution and poor soil. They leaf quickly in spring and here in Raymore Park, keep their leaves until November. Because of the dense shade they provide and their shallow roots, many native plants from wild flowers to trees cannot thrive in their vicinity. In addition, it is thought they may produce substances which make it harder for other plants to grow. They are still very common in Canada’s cities but an awareness of the damage that they cause has led Toronto and other cities to stop planting them. In Massachusetts and New Hampshire, planting Norway Maples is illegal.

These trees are so pervasive, they have even wormed their way onto our banknotes. Although the Canadian flag features a sugar maple leaf, the leaves on our banknotes resemble Norway maple leaves.

Identifying a Norway Maple.

A Norway maple leaf has 7 lobes. A broken stem will leak a milky sap.

A sugar maple leaf normally has 5 lobes.

Canada’s Flag with a stylized 5-lobed sugar maple leaf.

Not only are Norway maples bad for our native plants, their seeds are very fertile and can spring up just about anywhere. As a result, some park guardians actively remove saplings before they can become mature trees. They are also quite unstable – their branches can break easily. Their fall colouration is yellow rather than red.

In the meantime, the steady replacement of Norway maples with native shrubs and trees seems to be the best approach. Fortunately, they take 25-30 years before they start shedding seeds so that’s where early intervention helps. The City of Toronto recommends replacing Norway maples with native species such as sugar maple, red oak, and silver maple, or hybrids like the Freeman maple and Pin oak.

Finally, here’s how people in lower Montgomery County, PA. deal with Norway Maples:

Signs of Fall

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Fall looks as if it’s here to stay as temperatures are set to lower sharply next week. The first dip below zero of the season is forecast for October 30 which is slightly earlier than Toronto’s average of November 1-10.

Here are some recent images of the park as it eases into the approaching winter.

Colourful Boston ivy decorates the Humber footbridge entrance. October 2.

Sumac beginning to turn colour by the park entrance. October 2.

Two egrets and a blue heron. The egret (centre) was just about to chase the heron away. (October 12)

A lone egret with fall colours in the background. (October 24)

Norway Maple foliage is more colourful this year. October 28.

Today in Raymore Park

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A worker feeds branches of an elderly Norway Maple into a wood chipper.

A large Norway Maple by the parking lot is coming closer to the end of its life. The tree provides much needed shade but its days appear to be numbered as more rotten branches are found. It is the last of several large maples that once lined (and shaded) the parking lot.

Signs of Fall: tree planting

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In the last 20 years, thanks to old age and disease, there has been a steady reduction in the number of mature trees in Raymore Park. Quite a number of these trees are invasive non-natives such as Siberian elm and Norway maple. While many hundreds of native saplings have been mass planted in the wild areas, no mature boulevard trees have been planted to line the pathway.

On Monday September 23rd, 43 trees were planted along the entrance and pathway as far down as the weir. This will make a big difference in years to come as the path is quite exposed in both winter and summer. I only have one slight quibble with the choice of trees; quite a number are black walnut and the park has no shortage of those already. There are quite a few water-loving weeping willows where the path comes near the river and some maples too.

A couple of Toronto Forestry workers were inspecting the trees yesterday and they told me that for the most part the trees were planted to the correct specifications by the contractor. A few have been planted too high and will need to be adjusted and some look a little straggly, but for the most part it has been a successful planting.

This is the perfect time of year to plant trees as the ground is still warm and autumn rains will ensure lots of moisture for roots to grow.

Count ’em – 43 new trees!

Textures, invaders and regeneration

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Trees come and go in the park whether they are felled by old age, ice or by the latest foreign invader, new ones rise up and take their place. Many of the new ones are foreign invaders themselves.

Old wood returns to the earth surrounded by new growth.

Old wood slowly returns to the earth and feeds new growth.

Norway Maples have become ubiquitous in Eastern Canada – even to the point of having their leaf on our currency. They have been in Canada for hundreds of years and are able to grow more quickly and produce leaf earlier in the season than native trees. In addition, their shallow roots and dense shade have a smothering effect on native tree seedlings. As for Siberian / Chinese Elm, I can honestly say I must have killed thousands of saplings in their attempts to establish a beachhead in my back yard.

An old Norway Maple whose days are numbered.

An old Norway Maple with beautiful textured bark.

This old Norway Maple provides wonderful summer shade to cars in the Raymore parking lot but its age is showing and its hollowing interior has become home to more than a few squirrels. It drops the occasional limb now and then and will soon become a victim of old age. Unfortunately its replacement (if any) will take many years to provide the same cover. Hopefully the replacement will be from a native species.

Across the path from the parking lot attempts have been made to mass plant native trees and shrubs with varying degrees of success. Part of the problem is that the saplings (thanks to the availability of student labour) are planted at the hottest time of year. Last summer, a substantial batch of saplings was delivered to the planting site and left in plastic bags for a day in hot sunshine before being carefully planted. Needless to say, thanks to bad planning, only a tiny fraction survived, wasting a whole lot of time, effort and money.