Winter is the season when just about everything shuts down. Pools are closing, outdoor sports are done, and trees lose their leaves and go dormant for the winter. But evergreens do not lose their leaves in the fall, so how do they grow year round and during the winter?
Evergreens will grow during the winter and year-round. They do not lose their leaves or needles and can photosynthesize all year round. Photosynthesis is important for tree growth, as without the leaves and needles staying on the trees, evergreens could not grow all year round.
It is always nice to see a little greenery in the winter. In this article, we will cover how evergreens keep growing despite the cold weather. Let’s get to it!
How Do Evergreens Survive And Grow During Winter?
Not all evergreens are pine trees. There are plenty of evergreens that are shrubs and herbs like rhododendron and sedge. Other evergreen trees include American holly and Eastern red cedar, just to name a few.
There are also tropical evergreens such as some ferns and trees that are well adapted to areas with high rainfall.
These plants have the remarkable ability to continue growing while their neighbors die off or go dormant. So, how do evergreens grow during the winter while other trees do not?
Evergreen Trees Keep Their Leaves And Needles
One of the most delightful things about evergreens is seeing a bit of color and life in the dreary winter months. But it makes you wonder – why aren’t all trees evergreen if it means they can grow year-round?
Having leaves on a tree is extremely helpful in the warm months, but can be a liability in the cold months. The more leaves a tree has, the more water and nutrients it needs to keep the leaves healthy and alive.
This is not a problem in the spring and summer since rich minerals are being added to the soil, plenty of rain saturates the soil, and the sun is plentiful. As the ground grows colder and the environment gets dry, trees can die off quickly if they don’t protect themselves.
Just like how some animals hibernate in the winter and others grow a thick coat to keep warm, some trees survive by losing their leaves and going dormant while others, evergreens, use adaptation to survive.
Whether it’s mountain laurel or towering spruce, evergreens keep their leaves and needles instead of shedding them like deciduous trees.
Although, wouldn’t it mean the tree has to work extra hard to keep the leaves alive? Yes, but a few characteristics of the leaves help evergreens survive during the winter:
- Shape: Evergreens in colder climates typically have needles. Needles are shaped so they do not catch the wind as broad-leafed trees do. This helps the tree stay upright during icy snowstorms.
- Coating: The needles and leaves of evergreens have a waxy coating. This helps retain moisture far better than a deciduous tree leaf. This is especially important during the dry winter months.
- Texture: Needles are not enjoyable to eat. Birds, deer, and insects all shy away from the needles of evergreens unless they are very desperate for food. This helps protect the tree from browsing.
- Leaf-drop: Despite the name, evergreens do not keep their leaves indefinitely. Every 2-4 years, needles and leaves will drop off the plant and be replaced by new ones. However, because the leaves only drop every couple of years, they can capture sunlight for photosynthesis all year round.
So, evergreen trees keep their leaves all year. How does it help the tree grow during the winter? According to the Carnegie Museum of Natural History, photosynthesis is the key:
6CO2 + 6H2O → C6H12O6 + 6O2
Right… In simple terms, trees use their leaves to perform photosynthesis. The product of photosynthesis, sugar, is then converted into starch, and starch makes trees grow.
According to the Portland Government, for photosynthesis to take place, the tree needs three things:
- Carbon dioxide
The sunlight part of the equation is how the leaves help. They use chlorophyll to capture sunlight. Incidentally, the chlorophyll gives evergreens their eternally green color, too!
For information on what types of trees fall into the evergreen category, check out 6 Different Trees That Keep Their Leaves All Year.
Evergreens Use Snow To Keep Warm
Nothing about this title makes sense, right? Using snow to keep warm?! But it’s true: Evergreens that live in colder climates use snow to keep warm.
Have you ever been inside an igloo? Few have, but they can get pretty toasty inside, up into the ‘60s sometimes. Igloos use the same concept as trees – snow for warmth.
Snow comes in all shapes and sizes, but the basic stuff that makes up snow remains the same – water. Crystalized water to be exact. And the area around the crystals contains an extremely important element: air!
The air pockets around the crystalized water provide tons of insulation, especially when warmed by body heat. Sleeping bags, liners, and pads use the same concept to help keep you warm when sleeping on the ground.
Even though all snow is crystalized water, not all snow is the same. There’s wet snow and fluffy snow. Fluffy snow is the best type of snow for insulation because it is less dense than wet snow and therefore contains more air. More air = more insulation.
Evergreens thrive more during snowy winters than they do in dry, sunny winters. The blanket of snow around the evergreens acts as a blanket over the roots. This keeps the soil around the roots warm, preventing the roots from dying off.
Roots are the main gatherer of water, one of the three key elements of photosynthesis. Without water, trees cannot grow or hope to survive.
Keeping their leaves through the winter and using snow for warmth keeps evergreens cozy and happy through the winter.
If you’re wondering how other trees survive the winter, you can read our in-depth guide on how trees survive the winter here.
Do Evergreens Ever Stop Growing?
Evergreens seem to know exactly what they need to survive. If they can grow all year-round, do they ever stop growing?
Just like humans and animals, plants have a life expectancy too. Some can live for a few decades while others can live centuries and even millennia, which is the case of The General Sherman Tree, which is over 2,000 years old.
When you think of the growth rate of any animal, including humans, we see a pattern where growth happens quickly in youth and eventually halts as we get older. The same can be said for plants.
Shrubs, herbs, and trees will eventually slow their growth in height until it is barely noticeable. However, they never actually stop growing. The plant will continue to produce new limbs and, in a tree’s case, will continue to grow wider as they add growth rings to their trunk.
Why Evergreens Stop Growing
As we mentioned before, evergreens don’t really ‘stop’ growing so much as slow down their growth rate. But what causes this slowdown?
There are a few probable reasons an evergreen will stop growing in height at a certain age:
- Cells stop dividing
- The plant is too tall to sustain the transport of nutrients
- Unfavorable conditions
Let’s check those out in more detail.
Cells Stop Dividing, Limiting Evergreen Vertical Growth
On a molecular level, trees have cells and perform chemical reactions similar to any living thing. But eventually, the cells will stop dividing, halting the chemical processes needed for vertical growth.
This will only happen once the tree gets older. For example, a tree may have a lifespan of 200 years, but at age 80 it may slow its growth rate significantly if the cells aren’t dividing and creating new growth.
Evergreen Growth Will Slow When The Plant Is Too Tall To Transport Nutrients
Another reason evergreens might slow their vertical growth is they just get too tall. For the tree to grow, nutrients and water must travel from the roots to the tippy top of the tree.
On the way up, gravity is constantly battling with the pull from the leaves for water and nutrients. Eventually, gravity is going to win.
Unfavorable Conditions Can Slow Evergreen Growth
According to a study published in Tree Physiology, most plants and trees grow fastest in warm, humid conditions. The only exception is tropical plants because they live in this optimal environment all the time.
Temperature is only one factor that affects tree growth. Soil conditions, water content, and sun conditions will all affect plant growth rates as well.
Are Evergreens Always Green?
Through rain or shine, sleet or snow, evergreens seem to always be green! Is it true, or a trick of the eye?
In general, evergreens always have green leaves (including needles) on the plant/tree year-round. However, this does not mean the green color comes from the same leaves year after year.
According to the University of Georgia, evergreens shed their leaves and needles every few years. However, because the leaves last more than one year, the leaf drop is often unnoticeable to us because there’s so much new growth.
Each plant has its own rate of leaf drop, but the most common age of leaves is three years before they fall off. Sometimes the leaves will change to a brown or yellow color before dropping, showing they are ready to fall off.
Another inconsistency between evergreens is what season the leaves fall off. Some fall off in spring to prepare for fresh growth, others fall off in summer or fall to prepare for winter.
No matter when the leaves decide to drop, there are still tons of new growth to cover the yellowing or browning leaves, giving the plant an evergreen appearance.
What Are The Signs Of Winter Damage To My Evergreen?
Winter is by far the hardest season on plants, evergreen or not. The snow cover may help provide insulation, but it can also weigh down branches and even break them off if the snow or ice is heavy enough.
The bleak cold season can creep up on evergreens, so it’s important to be on the lookout for signs of winter stress so you can keep your evergreen happy, even during the coldest days.
Browning Leaves And Needles
Brown leaves are usually more noticeable on an evergreen than a deciduous tree.
The browning of evergreen leaves and needles can be caused by a few winter-inspired effects:
- Sun bleaching
- Frozen ground
- Dry conditions
The sun is an important element in tree health, so you would think those warm sunny days in the middle of winter would be good for evergreens.
The truth? Sunny days in winter can devastate evergreens. Sunny days in the spring and summer are great for an evergreen – there’s lots of water and nutrients available to promote new growth.
However, in winter, things slow down quite a bit. The soil gets colder, the roots struggle to find water if the ground is frozen, and minerals are harder to come by.
When chlorophyll absorbs sunlight to perform photosynthesis, it only needs as much sunlight as the tree can handle with little water and minerals. If it takes in too much, it can bleach the leaves, turning them brown.
This can happen from direct sunlight, or the light reflected off the snow. Ever heard of photokeratitis? Probably not, but you have probably heard of snow blindness – same thing.
According to the University of Utah, snow blindness happens when your eyes get sunburned. This happens most often when a bright sunny day is paired with fresh white snow on the ground.
In a sense, evergreens can experience snow blindness too. Trees do not have eyes to get burned, but their leaves can get fried from too much direct sunlight and reflected sunlight.
With this in mind, it is important to remember evergreens are adaptive. A study published in the Proceedings of the National Academy of Sciences revealed that evergreens have a way of protecting their chlorophyll from sunlight so it does not burn them brown so easily.
If the sunlight becomes too much for the chlorophyll, the evergreen will produce a complex molecule to take in the sunlight and dissipate it as harmless heat from the leaves. Pretty cool, right?
Unfortunately, not all evergreens have this ability. So, if your evergreen turns brown, it most likely cannot protect itself from plant snow blindness and is receiving too much light.
Brown leaves are not always caused by bleaching from the sun. Dry conditions can also turn an evergreen’s leaves a dreary brown.
Dryness happens when the ground freezes and the roots cannot take in water. Wind can also dry out evergreens, causing the leaves to turn brown.
Broken Branches Or Stems
If you are lucky enough (or unlucky enough, depending on your perspective) to live in an area with all four seasons, you are probably familiar with the yearly big snowstorm.
It happens once or twice a year when you get pounded with snow, sometimes ice, accumulating up to a foot or more. As a kid, it was the best thing ever, no school! But as an adult, you might just sigh and stare out the window with an impending sense of dread.
Evergreens dread big snowstorms as well. The heavy snow can weigh down stems and branches, putting extra stress on the evergreen. If the snow is wet, or if ice is involved, it’s even tougher on them.
Broken branches, stems, or leaves can occur during particularly heavy snow accumulations. This will damage the evergreen tree, severing important light-collecting leaves from the tree.
The wound left behind will take years to close, and in the meantime, insects and critters may move in. This can damage the interior of the tree and even kill it if the flow of nutrients is halted.
Soil Heaving Can Damage Evergreen Tree Roots
We have talked about how leaves and branches are damaged by winter weather. Now let’s discuss how the roots can be affected by Jack Frost.
In many areas where winter weather occurs, the temperature fluctuates from day to day. January and February are pretty cold, but November, December, March, and April can see vast fluctuations in temperature.
Naturally, the warming and cooling of the soil causes it to expand and contract, expand and contract, over and over again. This repeated growth and contraction of the soil will damage evergreen tree roots and can sometimes rip smaller plants right out of the ground!
How To Keep Your Evergreen Tree Growing In The Winter
An evergreen with browning leaves or broken branches, and root damage is not a happy tree. We want our trees to be happy, right?! After all, they give us oxygen, shade, and are nice to look at.
To keep your evergreen happy, you will want to take a few steps to protect it from the harsh winter conditions. Keep the following in mind when fall begins losing its grasp and winter takes hold:
- Choose the right location to plant your evergreen
- Protect your evergreen from sun, wind, cold temperatures, and snow
- Water your evergreen properly during the growing season
- Prune at the proper time
Let’s dive a little deeper into those topics so you can keep your evergreen green and happy!
Choosing The Right Location For Your Evergreen
If you are planning to purchase an evergreen and are wondering where to plant it, pay close attention to the north and northeast areas of your yard. This is where your evergreen will do best.
We all know the sun rises in the east and sets in the west, so planting your evergreen on the north/northeast side of your lawn will help shield it from the sun’s rays during the winter. This will help prevent bleaching of the leaves.
If there is a way to plant your evergreen so it is protected from the wind as well, all the better.
Protect Your Evergreen Using Boughs, Burlap, And Mulch
Deck the halls with boughs of holly… wait, what exactly are boughs? Boughs refer to the main limb or branch of a plant or tree. You can use boughs to protect your evergreen.
If there are any fallen branches or stems from other evergreens or trees, you can prop these against your current evergreen to protect it from the sun, wind, and snow. The bough will act as an extra layer of protection, absorbing some of the sun and protecting against wind and snow.
You can also use burlap to protect your evergreens. Burloptuous’s Natural Burlap Fabric is a brilliant choice for your evergreen. It comes in a 15-foot roll, so you can cut it to fit your evergreen, no matter the size and shape.
If you are not keen on cutting the burlap yourself, you can go for something like ANPHSIN’s 40 x 47 Inch Burlap Winter Plant Cover Bags. Just pop it over your plant and you’re done!
Putting a ring of mulch around your evergreen will help insulate the roots and keep the soil at a more even temperature. This prevents soil heaving and can go a long way in keeping your tree happy.
Water Your Evergreen Properly
Your evergreens will not thank you for being over-watered or under-watered. How do you know how much water your evergreen needs?
According to the University of Minnesota, you can measure the main stem or trunk of your plant at 6 inches above the ground (unless its diameter is greater than 4 inches, then measure at 1 foot above the ground.)
Depending on the diameter, their site will tell you how long it takes for the roots to establish and how many gallons of water you should use at irrigation times. For example, a 1-inch tree trunk will take 1.5 years to establish roots and require about 1 ½ gallons of water at each watering.
But how often do you water the plant or tree?
A good rule of thumb is to water daily if the plant is new. Between 3 and 12 weeks, water once or twice a week. After 3 months, water once a week until the roots are established, then you can stop watering and let nature take the reins.
Prune Your Evergreen At The Proper Time
Pruning is essential to a tree’s health. It may seem counterproductive, snipping off healthy stems and branches, but in the long run, it helps more than hurts.
Pruning encourages growth in any plant, including evergreens. However, you can’t prune all year long.
August is the last month you want to prune your evergreens. After this, evergreens slow down and harden off for winter, so you do not want them spending extra energy trying to grow more than they have to.
Evergreens are green all year and do not lose their leaves as often as deciduous trees. Instead, leaves and needles stay on for a few years before slowly falling off.
For deciduous plants, winter means a partial or complete halt to new growth as the plants go into a dormant state. They lose all their leaves and shut down, waiting for the warmth and rain of spring to wake them up and encourage new growth.
Evergreens do not go dormant like deciduous plants. Instead, they keep on trucking through winter. Their growth may slow, but they continue to photosynthesize and create sugars for new growth.
Whether you already have an established evergreen or are thinking of planting one, there are plenty of ways you can help it survive and thrive through winter, keeping a bit of color in your yard to contrast with the unexciting gray and white of winter.
Gilmore, A. M., & Ball, M. C. (2000, September 26). Protection and storage of chlorophyll in overwintering evergreens. Proceedings of the National Academy of Sciences of the United States of America, 97(20), 11098-11101.
Ninemets, U. (2016, March). Does the touch of cold make evergreen leaves tougher? Tree Physiology, 36(3), 267-272.
Ryan, M. G. (2010, June). Temperature and tree growth. Tree Physiology, 30(6), 667-668.
Starr, G., & Oberbauer, S. F. (2003, June 01). Photosynthesis of Arctic Evergreens Under Snow: Implications For Tundra Ecosystem Carbon Balance. Ecology, 84(6), 1415-1420.