Enjoying the urban forest in winter

Dec. 08, 2012 @ 10:47 AM

DURHAM -- Now that the leaves have mostly fallen and the leaf blowers are quieting down, it’s nice to note the seasonal changes to our landscape.  With the branches bare we can see into the crowns of our trees and get reacquainted with how their form follows function. We can also appreciate, in retrospect, the way  leaves absorb sound, light and air pollution, and block unwanted vistas into our neighbor’s yard.

Winter is also a nice time to appreciate the bounty of our trees, and this year we had a decent crop of acorns.  Really big nut crops, known as mast years, are a mysterious cyclical phenomenon involving trees across large regions producing a simultaneous bumper crop.   The general theory is that the trees do this to overwhelm the appetites of the local animals to insure a few nuts aren’t eaten and can grow.

Nobody knows what triggers a mast year. In fact, the timing of these can be downright spooky.  For example, the trees were absolutely full of acorns and nuts when Hurricane Fran blew through in 1996, knocking trees down and creating a lot of open space in the canopy for young trees to occupy. Coincidence?  I’m not so sure…

And, of course, acorns and other nuts provide important winter food for squirrels, deer, wild turkey and blue jays.  Winter is also a great time to watch woodpeckers and notice that bird nest from last spring, as well as a good time to look into your own trees to see if there’s any work to be done. 

Broken or dead branches hanging over your favorite parking space or roof can be addressed by a trained and competent arborist this time of year.  But be careful who you hire; while it takes a lot of skill and guts (and insurance) to cut a tree down, it also takes a lot of knowledge and care to prune a tree without causing unnecessary harm. To guarantee the latter skill-set, it’s best to go with a professional who has some accreditation with an organization like the Tree Care Industry Association (TCIA) or International Society of Arboriculture (ISA).  You can check their websites to locate their local members in good standing.    

Your mature trees aren’t the only ones which may be in need of attention. In order for trees to reach their full potential in the landscape, they do require early pruning.  These “training” sessions are necessary to encourage preferred shape.  Shape, or form, defects can lessen the value, functionality and overall lifespan of a tree and can be prevented by well-applied pruning cuts in the first seven years of a new tree’s life.   Now that leaves are off our hardwood trees, it might be time to consider what you want that tree to look like in a few years and take some steps (with some professional advice) to help it along.

As for all those leaves, why not view them as a resource, like the trees do?  Leaves eventually break down (especially after shredding) into very nice mulch.  This turns into organic topsoil, which increases the ground’s ability to soak up and hold moisture and exchange nutrients.  This all takes some patience, work and a bit of space to happen, but it sure beats buying soil and mulch in the spring when thoughts turn to gardening again.

In the meantime, enjoy the view!

Alex Johnson is urban forestry manager in the City of Durham’s General Services Department.