Keys - Samaras - Samares

Less than three weeks ago, I started posting about the maple trees in bloom. Well, they've wasted no time! I've been watching the samaras (samara: winged fruit) developing since about May 4.

Acer saccharinum samaras

Acer platanoides samaras

Acer negundo samaras

Samaras are a useful adaptation. Because of the thin, papery 'sail' portion, this seed will travel further from the tree than other types of nuts, allowing better dispersal of seeds and therefore a better territorial expansion for the population. Note that all maple keys are samaras, but not all samaras are maple keys; many other genera of trees produce samara, including the elms and ashes.

The photo below shows a close look on an A. saccharinum samara which was not successfully fertilized and so is not developing (note the small, shrivelled samara on the right-hand side). The tree does not invest energy in developing samaras which are not fertilized, as it would be wasted energy; an unfertilized samara that flies away from the tree won't result in a new tree, so there's no point in investing the energy.

A. saccharnum samaras

In some cases the samaras are developing before the leaves. This tree looks very green and filled out, but all of that green is from samaras, not leaves. Depending on the species, these samaras will take to the air throughout the spring and summer.

Acer saccharinum crown

Manitoba Maple - Acer negundo - Érable negundo

So the most recent tree to go into full bloom here in Montreal is Acer negundo (Manitoba maple). The long, pendulous male flowers are quite eye-catching at the moment.

Acer negundo staminate inflorescences

Like Acer saccharinum, A. negundo is wind-pollinated. Unlike A. saccharinum, A. negundo is dioecious [1,2,3], which means that each tree is either male or female. As with A. saccharinum (and other wind-pollinated species), the flowers are not perfumed or showy, as there is no point in investing energy in characteristics which are used exclusively to attract pollinators. Instead, wind-pollinated plants invest energy in producing a huge amount of pollen to make up for the tremendous inaccuracy of wind-pollination.

Acer negundo staminate inflorescence

A. negundo is introduced in this region, being native to places in the U.S. and in central Canada [native range map here]. This tree is a popular choice for landscaping, and because of this has been spread globally. This species takes very well to disturbed habitats and so has a tendency to spread in human-occupied land. A. negundo also prospers in riparian areas (transition zone from land to river). The species spreads easily and is naturalized in southern Quebec, New Brunswick, Nova Scotia, PEI, and various parts of the United States [3].

A. negundo staminate inflorescence

There is some variation in the timing of emergence of flowers and leaves in A. negundo, depending on geographical (climate) factors [3]. In some places, the flowers appear first, and then the flowers. As can be seen in the photos I have, at least here in Montreal, the flowers and leaves appear simultaneously; this is likely related to the shorter growing season here compared to more balmy southern climes.

A. negundo staminate inflorescence

Unlike most maples, A. negundo has distinctive compound leaves. Image of leaves here.