“When I see birches bend to left and right
Across the lines of straighter darker trees,
I like to think some boy’s been swinging them…”
-Robert Frost
While birches bow under the weight of snow and ice, what makes these “straighter darker trees” stay upright?
These are conifers, trees that produce cones, and many have a conical shape. Their tapered form is designed to shed snow and ice and is a result of their growth pattern. Many conifers (such as pines, firs, and spruces) grow in annual spurts, putting on a circular pattern, or whorl, of branches each year from a single shoot. As the tree grows upward adding whorls, the whorls of lower branches stretch further outwards. This shape allows these conifers to shed their load of snow and ice while keeping their stable cone structure. As ice and snow collect on the branches, they droop until touching the supportive whorl of branches below. The more ice and snow, the more the conifer is folded in, and the more ice and snow slides off the steep sides.
This whorling growth pattern also allows us to estimate the age of young conifers, usually up to around 15 years old. Start by counting the whorls of the tree. Look closely for any circular arrangement of stubs and/or knots at the bottom of the stem where early branches had grown and then died and dropped off, and add that number to your age count. Add two to four years for the time of seedling germination to branch whorls to get your final age estimate.
