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Why Do the Leaves Change Color on Some Oregon Trees?

As summer comes to a close, Oregon trees celebrate by filling the skies with an explosion of reds, oranges, and yellows. Mid to late October is typically the peak season to observe the changing colors of the Oregon foliage.

As winter approaches, trees start preparing for the cold weather by conserving energy and food reserves. This phenomenon of nature taking drastic measures to protect itself against the elements results in the beautiful bright colors we enjoy in autumn.

Why Do the Leaves on Some Oregon Trees Change Colo

As brilliant as these colors are, they conceal the stress that the trees suffer from the preparation of a winter onslaught. These cold months take a toll on your trees’ health, and the assistance of a good tree service in Oregon can help you take care of and keep your trees maintained during this season.

You might have noticed, however, that not all Oregon trees participate in this celebration of colors, and some trees remain green. This difference is due to the wide variety of trees that are native to Oregon. Coniferous or evergreen trees retain both leaves and color during winters. Although Oregon is most famous for its forests of coniferous trees, a number of native Oregon trees also happen to be deciduous – these are the trees whose leaves change color and shed every autumn.

Why Leaves Change Color

The change in the colors of leaves during fall is a defense mechanism for trees to protect themselves from the impending winter. To understand precisely how that happens, we will need to get into some technical details of the inner workings of a tree.

It is common knowledge that trees get nutrition through a chemical process called photosynthesis, which converts carbon dioxide, water, and light into sugar and oxygen. This process involves a pigment called chlorophyll, which is also responsible for the green color of tree leaves.

In some places, typically in higher altitudes, days become very short and sunlight becomes too scarce for plants to undergo enough photosynthesis to produce food to keep the entire tree nourished. So, they adapt to the shortage of food by shedding leaves and conserving their limited resources to keep the rest of the tree healthy.

The trigger for this self-preserving activity is decreasing daylight; as the days get shorter and the nights get longer, the trees sense the ending of summer and the beginning of winter. At this point, the trees start collecting food generated from the leaves and stop supplying further food to the leaves.

Now, plants contain a number of pigments apart from chlorophyll, like carotenoids, the pigment responsible for giving carrots their orange and bananas their yellow hues. As photosynthesis forms the majority of functions executed by plants, the sheer quantity of the green pigment, chlorophyll, masks the other pigments already present in leaves.

As daylight shortens, the veins that supply food and oxygen to the leaves start closing off, causing chlorophyll to break down and reducing its dominance over the other pigments. This leads the leaves to reveal their underlying orange and yellow shades, which were always present, only concealed.

Another unexpected thing that happens when the veins in the leaves start closing is that the remaining sugars get trapped inside the leaves. The reaction of these sugars with other chemicals results in the formation of anthocyanin. This is the pigment responsible for giving plants the red and purple colors you see – like the red in berries and the purple in grapes. It is formed in leaves only during autumn.

The effect of anthocyanin varies by temperature. Low temperatures above freezing help in the formation of more anthocyanin, making the reds deeper and more vibrant.

The exact colors of leaves in different trees vary due to the combination of these pigments with the remnants of chlorophyll and variables like temperature and tree species. For instance, in Oregon, trees like birch tend to have yellow leaves while vine maples a brilliant red color. To conserve the water collected by trees, the chilly weather triggers a hormone which allows the shedding of leaves.

Eventually, as the food reserves in the leaves deplete, the sun and the frost destroy all other pigments leaving only tannins, which gives leaves a brown color.

In comparison, most conifers are evergreen year-round and their narrow leaves, which might stay on for over two years, retain a greenish color in this season. Evergreen trees do not shed leaves all at once during fall, but continue shedding leaves little by little throughout the year.

The wax-coated needle-like leaves offer a very small surface area to the sun, which reduces the amount of water evaporated from the leaves. Also, these trees contain anti-freeze chemicals which keep the tree roots and leaves alive during the cold weather.

Trees in Oregon

Oregon has a diverse climate, making it home for a lot of different varieties of trees, and almost all of them can be divided into conifers and deciduous trees. The most common tree in Oregon is the Douglas Fir, which is a conifer and also Oregon’s state tree.

Among deciduous Oregon trees, Bigleaf maples, birch, ash, aspen, and alder turn yellow; Dogwoods turn burgundy; Vine maples and huckleberries turn red; Oaks turn orange.

The state becomes a veritable festival of colors.

Tree Maintenance in The Fall

In autumn, trees appear to be alive with color, but looks can be deceiving. This is the period when trees transition from very hot weather to very cold weather, making them weak and susceptible to diseases.

Trees should be well taken care of to avoid suffering during extreme winter storms. Pruning in fall can protect trees from harsh winter storms, and the exposed tree structure during this time makes it an excellent time to prune your trees.

Accepting help from a knowledgeable tree service provider like Mr. Tree will take away all your stress about maintaining your greenery, letting you enjoy the gorgeous sights offered by this wonderful season.