Norway Maple - Acer platanoides - Érable plane

This maple has been blooming vigorously in Montreal for a little over a week now, no surprise as it is an early bloomer.

A. platanoides

Though it looks similar to the native Acer saccharum (sugar maple), this species is an introduced ornamental which is extremely popular in cities for its tolerance to a wide variety of environmental conditions [1]. The species is native to eastern and central Europe [2], but is naturalized in parts of North America particularly the northeastern US [1,3]. Exact distribution maps for this species are unfortunately not available at present; due to its popularity as an ornamental and its potential to spread into wild habitats as a result of its introduction in lanscaped areas, it is not presently known exactly how widely distributed the species is [4]. At any rate, it is classed as an invasive species in the US [1,2,3,4] and Canada [1,2,4]

A. platanoides flowers

A. platanoides ornamental varieties with red leaves such as the popular Crimson King cultivar [5] have been bred as well and are very popular.

A. platanoidies, cultivar Crimson King

This species' invasiveness is cause for some concern, particularly as it inhibits understory plants beneath it [1,3,4] and could not only crowd out native maple species such as the economically important A. saccharum (sugar maple, the source of maple syrup), but also other native trees such as beech [1,3,4]. There is the possibility that an observed reduction in understory diversity below A. platanoides could also result in loss of understory herbs and shrubs, but at present there isn't any data to back the idea up [4].

A. platanoides, cultivar Crimson King : flowers

This is an animal-pollinated species[1,4], visited by Bombus spp. and Andrena spp. [1]. That it is animal-pollinated rather than wind-pollinated shows in the structure of its flowers. Note the presence of sepals, petals, stamens, and pistils -- these are 'perfect' or 'complete' flowers, bearing all of the basic characteristics of a standard animal-pollinated flower (note that they are also monoecious, as indicated by the presence of both male -- stamen -- and female -- pistil -- parts on the same flower and tree) :

Complete flowers on A. platanoides - note that though the pistil is small, it is present

The pistil is a bit more visible in the flowers of the cultivar Crimson King. It's the red part in the centre:

Complete flower on A. platanoides, cultivar Crimson King

The simplest method for an amateur to distinguish between A. platanoides and A. saccharum is to break one of the leaves from the stem and squeeze a bit; if the sap is clear, it's A. saccharum, whereas if the sap is milky, it's A. platanoides [1,3,5].