Trees and shrubs are classified as either evergreen or deciduous. A deciduous tree loses its leaves in the fall and new leaves appear in the spring. The term “evergreen” describes trees that retain their color throughout the year, and are often able to endure cold weather and dry seasons.
Evergreen trees can be either broadleaf or needled. Although called evergreen, the leaves or needles of these trees are not always green. The Colorado blue spruce, for example, is classified as an evergreen but its needles are a silvery blue color. Conifer trees may be evergreen, but some are deciduous.1
The variety in these trees makes them a perfect addition to your garden as they retain the architectural lines defining the structure of your garden year-round. Evergreens are found on every continent except Antarctica and are valuable resources, providing lumber, medicinal ingredients and food.2
While a leaf may remain on an evergreen tree for two years or longer, they do eventually fall off and are replaced. This may happen during any season of the year. Evergreens are important to birds, which use them for cover during the cold winter months.
Birds also seek shelter in warmer climates on unusually cold nights. The dense needles or leaves on the evergreen offer protection from rain, wind and snow. Since evergreens come in all sizes and shapes, you’ll likely find something that fits well in your garden.
Choose your tree to match your needs
Most evergreens require very little care. But before going out to purchase trees or shrubs for your garden, it’s important to determine the purpose in your landscape. Do you want a windbreak for your house to reduce your electric bill? Would you like screening and privacy from the neighbors? Or will these trees be decorative, providing an anchor for your garden?3
Since the trees come in a variety of shapes, sizes, colors and leaf types, understanding the purpose for which they’ll be used will help determine the tree types that will work best in your yard. Although they survive in a wide variety of growing zones, most thrive in specific zones.
Your trees are part of your landscape, so you’ll likely want rich, full trees or shrubs, and not spindly plants that appear to just be hanging on. The nursery where you purchase your evergreen trees will likely have a good understanding of the hardiness zones where the trees you choose will thrive.
If purchasing online, be sure to do your own research on the hardiness zones. You’ll find the hardiness zone where you live on the U.S. Department of Agriculture’s Plant Hardiness Zone Map.4
Consider your soil
As you choose your evergreen trees or shrubs, remember some may tolerate dry soils while others need a moist environment. Some trees prefer acidic soil, whereas others require a more alkaline type. Interestingly, trees that thrive in dry soil also enjoy alkaline soil, so if your area has dry soil and tests alkaline, it’s best to consider drought-resistant trees.5
On the other hand, acidic soil tends to hold more moisture, so evergreens that grow best in acidic soil must also like it moist. However, if you have your heart set on a specific tree that prefers an environment opposite to what you have in your garden, you might consider changing your soil’s pH to adjust for your tree or shrub.6
The pH is a measurement of alkalinity or acidity and the scale ranges from 0 to 14. A pH of 7 is neutral, below which is acidic and above is alkaline. The soil pH affects the availability of nutrients to the plant, and most essential nutrients are best available between a pH of 6 to 7.5.
Before attempting to change your soil pH, it’s best to have it tested. If it’s alkaline, you may increase the acidity by adding elemental sulfur, organic mulch or sphagnum peat. If your pH is highly acidic, you may raise it by incorporating limestone into the soil. Be careful not to add too much of either, though, as it may damage your plants.
Wood ash also raises your soil’s pH. Modifying the pH is a process often requiring repeated treatments over time. It may also be necessary to treat the soil around your trees each year after they’ve been planted, but remember to test first to avoid damaging them.7
How much care will your tree require?
Most varieties thrive in full sun to partial sunlight. Some have a higher tolerance than others for sun exposure, extreme weather conditions, and pests and insects. Your trees will require regular watering through the summer, especially during dry seasons. They also appreciate mulching to fortify the roots from injury during winter or from the drying effects of wind and sun.8
Evergreen trees don’t usually require fertilization, but if new growth is showing slowly, you may find fertilizing to be beneficial. Purchase and plant your tree or shrub in the spring, summer or very early fall, so it will have time to establish roots. This will also reduce the risk of injury during the winter.
When you bring your evergreen home, it will likely come with the roots balled in a burlap bag or in a pot. The hole you dig should be as deep as the root ball and at least two to three times wider.9 After planting, regularly water the tree during the first year. A good soaking once a week, especially during dry periods, is usually enough.
The tree will appreciate 1 to 3 inches of water every week when it doesn’t rain.10 It’s important to soak the soil once or twice a week to encourage the roots to go deep rather than to irrigate on a daily basis.
Use a drip irrigation system or soaker hose to allow the soil to absorb as much water as possible through the watering. Dumping large amounts of water on the soil only encourages runoff. Evergreen trees could be watered at night with a soaker hose to avoid moisture loss due to evaporation during the day.11
Prune your trees for best results
Most evergreen trees and shrubs will require yearly pruning to keep them in good condition and in your desired size or shape. Most have a strong central branch that requires pruning only to control the height, trim into shapes or increase the density of the remainder of the tree or shrub.12
It’s important to identify your evergreen species to understand the growth habits before pruning or you may lose the natural shape and beauty. For the most part, new growth will extend from buds formed during the previous year at the tips of the branches and twigs.
However, there are a few species capable of producing new growth on old wood. Most types of evergreen may be pruned in the early spring before growth starts, or during the semi-dormant period in the middle of the summer.
It is ideal to follow the natural shape of other evergreen trees or shrubs, remove any dead or diseased branches and allow the cuts on the branches to heal to form buds for the following year. Unless you have an evergreen you’re using as a hedge, selectively pruning one branch at a time is better than shearing.13
Pine trees have different pruning requirements.14 Most pine trees will produce buds at the end of the shoots and not along the stems. To produce a compact pine or maintain a shape, one-third to one-half of each new shoot may be cut off as it grows in the spring. Don’t prune back into the wood as new growth will not develop from this area. It’s not recommended to shear pine trees.15
Large evergreens — Screening, privacy and decoration in one tree
Evergreen trees add color and visual interest to your garden during the winter when everything else has died off. You’ll find evergreen trees in almost every region of the world and some have become garden favorites.
Conifers are likely the type of evergreen tree you would most readily recognize. There are nearly 630 species of conifer trees, several dozen of which are popular in the garden. When most people think about an evergreen tree, a conifer likely springs to mind. They range in size from dwarf fir trees to massive Scotch Pines, reaching over 150 feet high.
Conifers are identified by cones, which are an elaborate system of protecting their seeds. The leaves are often in the form of needles or scales. While they may be less efficient in producing nutrients for the plant, they are better able to withstand cold and hot, dry weather. Some of the most common Conifer trees include:16
- Hemlock trees — These trees are easily distinguished by their furrowed, cinnamon-colored bark. The foliage is flat and the branches come out horizontally and then bend downward.
- Cypress trees — These grow in the shape of a pyramid with small, round woody cones. Their leaves range from yellow green to a grayish color and may reach heights of up to 60 feet. Cypress trees enjoy full to partial light and are grown well in hardiness zones 4 to 11.
- Spruce trees — These also grow in a pyramid shape and are best known for their whorled branches and needles attached in a spiral formation. They may grow from 5 feet to 60-plus feet and are usually thought of as Christmas trees, especially the Blue and Norway spruce.
- Redwoods — These are officially among the oldest living trees. Old growth redwoods may be seen at Big Basin Redwood State Park in California and in the Santa Cruz mountains.17
- Pine — There are approximately 120 species of pine trees distributed throughout the world, but most are native to northern temperate regions.18 Pine trees are sources of turpentine, rosin, paper products and wood tars. Pine leaf oil has been used medicinally as an antimicrobial, antifungal and antibacterial.
While most varieties of broadleaf trees are deciduous, some stay green all year round. The leaves will be smaller and have adapted to resist the cold. Many species of holly are deciduous, but the European Holly is evergreen.
It became popular as a Christmas decoration when Roman soldiers wanted to celebrate the New Year with traditional green branches. Although it easily grows in Italy’s warmer climate, holly was a substitute in northern Europe.19 Rhododendrons also have species including evergreen varieties.
Dwarf varieties may help develop strong lines for your garden
As you create your garden, consider using dwarf evergreen trees to add color throughout the year and to define the architectural bones. These low-to-the-ground, always-green shrubs may be a feature of their own or may help to move your eye from one area of the garden to the next.
The recent growth in popularity has likely been from the variety now available in dwarf size shrubs and trees. These trees mature to a height of 12 feet or less and grow slowly. The ideal time to plant is while they’re dormant in October through March. Most will prefer full sun and a slightly acidic soil. Breeders are developing new varieties every year. Here are a few described by The Spruce:20
- Hudsonia — This slow-growing balsam fir tops out at 1 foot tall and 2 feet wide and is perfect for small gardens. It is among the most pleasantly aromatic evergreens, thriving in hardiness zones 3 to 7.
- Hertz Midget — This is one of the smallest evergreens, growing as a tight round ball 1 foot tall and wide. It is a smart choice for a small garden and easily tolerates some shade. It grows in hardiness zones 2 to 8.
- Pendula — This Canadian hemlock tree is hardy, growing 3 feet tall and 8 feet wide. Given the opportunity it may drape over a wall. It grows well in hardiness zones 3 to 7.
- Minnima Aurea — This bright yellow, false cypress grows 2 feet tall and 1 foot wide in a pyramidal shape, lending a bit of height to your garden. It is easy to grow and care for but doesn’t like exposure to strong winds. It grows well in hardiness zones 4 to 8.
- Rheingold — This evergreen has a rich gold color, mellowing to copper in the fall. It grows 3 feet tall and wide, and as the branches grow straight up it has a more conical appearance than a round shrub. It grows in hardiness zones 3 to 8.
Natural pest and disease control strategies
Evergreen trees are relatively easy to care for. However, they are also vulnerable to insect attacks. The best way to treat the condition is to identify the problem and use a specific, natural control to eliminate the problem without damaging the remainder of your garden. Some of the more common insect problems include:21
Aphids — These appear mostly on spruce and pine trees and usually in groups. They secrete a shiny, sticky material present on the leaves or beneath the tree. A blast of water from your hose helps dislodge them to the dirt where they ultimately will die.22
For a large population of aphids, dust the plant with flour as it constipates the insects. You may also try spraying the plant with a mild solution of water and a few drops of dish soap every two to three days for two weeks. You may help prevent them by planting catnip nearby or attracting their natural predators — lady beetles and parasitic wasps.
Bagworm — These appear on red cedar, juniper, spruce and pine trees. You’ll notice the foliage begins turning brown or is missing. Bags covered with dead foliage up to 2 inches long will be hanging from the branches of your tree. These are actually caterpillars from a variety of moth species.23
Control is most effective in the early spring or late fall. Add 2 tablespoons of dish soap to 1 gallon of water. Pour the solution into a garden sprayer. Find a long stick to puncture the bag open and then saturate the inside with the soap mixture.24
Spruce spider mite — These appear on spruce, pine, juniper and other conifer trees. You’ll notice a yellow speckling along the needles, more commonly on the base of the needle in early summer. The mites are usually present in early spring and late fall but not in the summer months.
They live on the underside of the leaves. Use a strong spray from your hose, or spray the leaves with a garden sprayer loaded with 3 tablespoons of dish soap to 1 gallon of water, being sure to soak the underside of the foliage.25