Pine trees and most other conifers are certainly defined as evergreen, but this does not mean the needles last forever. Here I will explain some basic differences between your maple and your pine.
“Broadleaf” and “conifer” are two terms used to describe tree leaves. Every tree fits loosely into one of these two categories. Broadleafed trees, such as maple and oak, have wide, flat leaves. Conifers, such as spruce and pine, have narrow, long needles. These are two different strategies at accomplishing the same task — photosynthesis.
Without going into advanced botany, here’s how they work:
– Needles give conifers an advantage on nutrient-poor growing sites and in cold, windy climates such as the Rocky Mountains.
– Large, flat leaves give broadleaf trees an advantage in nutrient-rich, hot climates such as the rainforest.
There exists an abundance of climates between those two examples where both types may thrive, including northern Indiana, which is relatively nutrient-rich but has cold winters and well-defined seasons.
Here in the northern U.S., all native broadleaf trees such as maples are deciduous, which means their leaf drop is influenced by the shortening of daylight hours and cooling daily temperatures and occurs on an annual, predictable basis. However, in the southern U.S., many varieties of broadleafed trees are evergreen, such as rhododendron and live oak, and do not shed their leaves for winter, just as most conifers do not. So, not all broadleaf trees are deciduous.
Most conifers such as pine, spruce, fir and cedar are evergreen, which means their needles (needles are a type of leaf) do not all drop at once, but rather are shed as the new season’s growth takes over responsibility for photosynthesis. This trait varies between species and is influenced by environmental factors, but when you look at any pine or spruce, you are usually seeing the needles produced only in the last 3 to 5 years. All the needles produced before that time have been shed as they age, wear down from the elements, become inefficient or are shaded out by the tree itself.
An exception among conifers present in northern Indiana would be the the tamarack, which loses its needles each fall after turning a beautifully bright copper color.
Both needles and broadleafs have advantages and disadvantages. Most yards have that certain spot where you just can’t seem to keep your favorite type of tree alive. Consider planting the opposite and you may find it thrives. We are fortunate to live in a climate that allows for a unique diversity of trees.
KEITH O’HERRIN is the City Forester for the City of LaPorte. He can be found at the Park and Recreation Office at 250 Pine Lake Ave. or reached at 326-9600.