Red Maples Are Complicated | Outside My Window


Male red maple flowers fallen from the tree, 10 April 2019 (photo by Kate St. John)

This week the hillsides turned faintly red as red maples (Acer rubrum) bloomed across southwestern Pennsylvania. The city’s maples bloom sooner than the suburbs so I’ve had a preview of what’s to come.

In Schenley Park the ground under some red maples is carpeted with fallen flowers (above) while others retain flowers that are setting seed (below).

Female red maple flowers on the tree, developing samaras, 10 April 2019 (photo by Kate St. John)

That’s because red maples are sexually complicated. They are polygamodioecious which means some trees have only male flowers, some have only female, and some have both (i.e. hermaphroditic). And they can even switch back and forth:

Under the proper conditions, the tree can sometimes switch from male to female, male to hermaphroditic, and hermaphroditic to female.

Wikipedia Acer Rubrum

Watch your local red maples to see what they’re up to. The one in my backyard dropped its flowers a few days ago. This year it’s a male. 😉

p.s. For more on maple phenology, read Chuck Tague’s blog post: Maples In Spring: A Study in Diversity.

(photos by Kate St. John)