Nature News: Red maple buds enjoying the last days of dormancy before budburst

I have a bad habit of always looking to the future, winter isn’t over yet but I’ve found myself starting to think about signs of spring to come. 

As an exercise in centering myself in the here and now, especially since we are finally in the middle of a beautiful snowy winter, I wandered around my backyard appreciating what the woods had to offer. I found animal tracks and hemlocks still encased in ice. The waterfall, covered with a blanket of snow, could be heard gurgling underneath and river ice cracked and boomed. A hint of color, in addition to the green conifers, was provided by the brilliant red buds of the red maple trees.   

Red maple buds as they appear this week, in late February, in Maine. Dormant and waiting for the longer, warmer days of spring to burst. Sue Pike Photo

Project Budburst is a great way to get involved in citizen science!

Last March, I started a three-month bud-watch project with my students in an attempt to get them outside, doing science as we plunged into remote learning. I participated as well. I found a beautiful young red maple tree with some bright red buds dangling at eye level and decided to follow those, entering weekly information about the state of the buds into an online citizen science database called Project Budburst (budburst.org). While doing this, I felt like I really got to know this tree. I even (rather uncreatively) named one particular bud “Red” and another “Rosie.” So, I visited Red and Rosie Jr. (new buds on the same twig) this past week to see how they were getting on.  

They were both there, chilling out in the wintry weather. I could count the number of rings around the twig that are the remnants of previous years’ terminal buds (the buds like Red and Rosie that emerge from the tip of the twig). Using these rings, I was able to figure out that the twig itself was about three years old and also see where this twig had added about an inch of new growth to where the buds formed last year.   

I had recently read an article (“The Sex Life of the Red Maple” by Richard Primack of Harvard’s Arnold Arboretum) that got me wondering what gender these buds actually are.

 Red maples usually have all male or all female flowers, but some are a mix of both (called perfect flowers) and sometimes a supposedly all-male tree will produce fruit.  Last spring when I named them, I was more focused on when these buds were breaking (opening up) than considering their gender. So I checked my photos of the buds in flower from last year and found that both Red and Rosie were male flowers with the characteristic stamen composed of a long, thin filament supporting the anther – a narrow disk that contains the pollen. This doesn’t mean the whole tree is male. Red maples are notorious for not following strict gender roles. I’m looking forward to checking later this spring to see if these still are producing male flowers or whether they’ve switched to female flowers.

The same buds as above–Red is top left, Rosie is lower right–at the end of last April (2020). You can tell that the buds that have flowers aer males by the long stamen composed of a thin filament and pollen-carrying disk-shaped anther. Sue Pike Photo

But, bud burst will happen later; right now, the buds are still dormant. 

Buds are wonderful structures, resilient little capsules that surround and protect the embryonic flowers and leaves. The outer part is actually made of modified leaves, called bud scales, that are tough enough to keep out insect pests and also help insulate the inner tissues. These buds formed last fall at the end of the growing season when the trees had enough food and energy to make the buds. This is a critical strategy for overwintering. Trees can’t wait until the spring to make these structures – they won’t have enough leaves and there isn’t enough light. So instead, in the fall everything the tree needs to flower and reproduce, to form its first leaves and start to photosynthesize, is packed inside those tiny buds, dormant now, waiting for warmer and longer days to burst into new growth.

I like to think that, like me, those nascent flowers and leaves are cozily wrapped up in their buds, enjoying the lazy days of winter while dreaming about spring.

Published February 24, 2021 in seacoastonline.com, the York Weekly, Fosters’ Daily & the Portsmouth Herald.

Birch Trees Bending

Published in the York Weekly, Portsmouth Herald, Foster’s Daily (and more) Dec 14 2020

I went up to Blue Job Mountain State Park for a walk last weekend.  There was a lot more snow up there than where I live in North Berwick.  Lining the parking lot were the birch trees, bent over, touching the ground, with their heavy loads of icy snow.   Hiking up to the summit of Little Blue Job was an obstacle course as we worked our way around all different types of trees, some were flexible like the birch and bent by the snow, some had snapped.  

Birch and beech saplings on a snowy afternoon

And they seem not to break; though once they are bowed.

This got me thinking about birches.  They are known for bending and not breaking.  Most of us read Robert Frost’s poem about boys swinging on birches in high school, but there is a part about the birches themselves  “Shattering and avalanching on the snow crust—Such heaps of broken glass to sweep away.  You’d think the inner dome of heaven had fallen.  They are dragged to the withered bracken by the load,  And they seem not to break; though once they are bowed.” where Frost talks about how birches bend and aren’t broken by the snow.  He talks about how sometimes they stay bowed after a long winter “So low for long, they never right themselves:  You may see their trunks arching in the woods.  Years afterwards, trailing their leaves on the ground.”  The sad thing was, people had made it worse by walking over their heads, cementing them into the icy trails.  Many were snapped by the weight of feet and all it would have taken was that first person on the trail to free the birches from their icy load, pull them out of the snow and let them spring back up towards the light.  

Adaptations to the North

This ability of birches to bend is an adaptation to living in the north.  We have a number of different species of birch in New England, among them, paper birch (Betula papyrifera), is one of our most widely-distributed trees, found from Newfoundland west to British Columbia and south to New York and South Dakota.  It is also one of a handful of broad-leaved trees that can live in the far north.  It  can live so far to the north because of those flexible branches.  Its northern neighbors, balsam fir and hemlocks, have a different adaptation to the same conditions and are cone-shaped; their long sloping branches help snow slide off instead of collecting on the branches and causing them to snap. 

Hemlocks conical shape lets snow slide off (eventually!)

Flexibility isn’t a paper birches’ only adaptation to northern climates.  During cold winters the thick, dark bark of an oak or ash becomes a liability, absorbing sunlight during the day and heating up, only to cool down again, usually quite rapidly, at night. This heating and cooling can kill the cells of the cambium, the layer of cells between the bark and the wood that is responsible for the growth of the trunk. Rapid temperature fluctuations can also severely injure a tree by causing frost cracks to form in the bark.

In contrast, the highly reflective, light-colored bark of a paper birch doesn’t absorb the sun’s radiation and heat on cold winter days, and so avoids the damage caused by rapid heating and cooling.

What causes this extreme whiteness? That white powder that coats the bark is primarily composed of a chemical called betulin. The cells in the outer layers of bark contain betulin crystals that are arranged in such a way as to reflect light and appear white.

Free the Trees!!

My walking partner is a tree enthusiast.  She felt sorry for all those forlorn birches bending under their heavy loads, and even more sorry for the birch tops that had been cemented into the trails by uncaring feet, or even worse, those that had snapped due to this trammeling.  She started clearing as many as she could.  Pulling the tops out of the snow and letting the trees spring free.  It was exhilarating and infectious to watch.  I joined in and we spent more of our time freeing birches than walking.  I don’t know whether this really will help the trees survive the winter, but figure it can’t hurt.   I’ve read that Frost once said “it was almost sacrilegious climbing a birch tree till it bent, till it gave and swooped to the ground, but that’s what boys did in those days”.  I agree, it is sacrilegious, and feel like now we should know better.  Trees have a hard enough time these days, if you see one struggling with the snow, why not help it out?

Stephanie Eno clearing snow from bowed maple and birch saplings