We had a few nights with below freezing temperatures last week, but that didn’t slow up one of our earliest spring bloomers. Red Maple (Acer rubrum) started blooming in early April and this bit of cold wasn’t enough to interfere with seed development on these trees in central and southwestern Ontario.
The flowers start out as tight red buds, often appearing as clusters on dwarf shoots on last year’s reddish-brown twigs, adding a bit of colour to the twigs, even before they bloom. They are conspicuous, visible from the ground, even on large trees. As the buds expand, exposing the flowers, the tree canopy takes on a subtle red hue, before any leaves begin to unfurl.
Red maple twig showing swollen flower buds 
A red haze of red maple flowers in the tree canopy
Both male and female flowers can be found on the same tree, a condition called ‘momoecious’, but the most common occurrence is for trees to have only all male or all female flowers – called ‘dioecious’. They don’t look the way you expect flowers to look; they look like little red (or red and yellow) pom-poms.
Close-up of twig with red maple male flowers showing “stamens” with pollen 
Close-up of Female flowers showing red “pistils”
The male trees bear pollen-laden flowers; the female flowers will develop into red, winged samaras (seed) when pollinated. Pollination is primarily by the wind as there are very few natural pollinators present at this time; but honey bees do visit red maple trees.
In early May, as the male flowers fade and wither on some trees, red maple seed begins to form on adjacent trees. After the flowers are pollinated, the female flowers produce tiny, pinkish-red samaras, that dangle on long ‘pedicels’ (stalks). The masses of these gives the trees the appearance of still being in bloom.
Immature seed begins to form 
Early stages of red maple seed development 
Seed continues to form on long ‘pedicels’ (stalks)
Within a few weeks, they develop into paired samaras with colours ranging from pale green with a pinkish margin on some trees to other trees having bright red samaras. Depending on the spring weather we get, the seed will be fully mature by the end of May to early June.
Mid-stages of red maple seed development 
Seed is in latter stages of development. 
Seed is in latter stages of development.
The colour of the seed samaras (2.0-3.0 cm long) change to a pale reddish brown to straw brown at maturity. The pedicels that connect the samaras to the tree then become dry and brittle. Within a few days, the seed will begin to fall from the tree or be dispersed by the wind.
Red maple is so-named for its red winter twigs and buds, red flowers and for its tendency to have red summer petioles and vibrant red fall foliage.