Are your evergreens looking yellow or brown? This might be why…
Extreme temperature changes over short periods of time during winter months can leave evergreen trees looking a little yellow and sad. There are a number of different reasons an evergreen tree might be turning yellow/brown and/or dropping needles this time of year. Sometimes it’s perfectly healthy, other times it’s not. How do you tell the difference, and what should you do? Here’s a few tips:
Needle Cast: If your conifer (pine, spruce, fir, or juniper) is dropping needles, it may be a perfectly normal and healthy occurrence. If the needles that are dropping are only on the interior part of the tree while the needles toward the ends of the branches are still flexible, green, and firmly attached, then your tree is going through a process called “needle cast.” This process is kind of like deciduous trees casting off their leaves every fall – the needles deepest inside the tree no longer receive much in the way of sunlight as they are shaded by the newer exterior needles, so the tree drops them. This is totally normal and you should not be alarmed.
Sun Scald: If the needles on one side of the tree are showing yellow or brown coloration, but the other side of the tree still looks healthy, it could be suffering from sun scald. The exceptionally dry winter air combined with low soil moisture and intense sun causes the needles to dry out. The damage is often only present on the most exposed parts of the tree where prevailing winds or southern sun can have the greatest impact. Often, only the tip of the needle will be discolored while the base of the needle remains green.
Some of this damage may be inevitable, depending on the location of the tree, but it can be mitigated by good winter watering. For particularly sensitive evergreens like boxwoods, arborvitae, and oriental spruce, to name a few, a permeable fabric like burlap can be used to wrap the plants, providing a little extra protection. Trees can also be treated with Wilt-Pruf, a product designed to give evergreen plants an added layer of protection on their needles and leaves. Generally, this type of damage is only short-term. Only in extreme cases do we start to worry about the overall health of the tree.
Freeze Damage: If your tree is dropping needles or yellowing/browning uniformly around the entire plant, there’s a chance the recent deep freeze caused such a shock to your tree that the needles were damaged.
When plants go through such a rapid change in temperature, they don’t have time to undergo the physiological changes that help them tolerate the cold. Cell walls can rupture when they freeze and the dry air can cause damage more easily than would otherwise be the case. In instances like this, the damage will be most prominent on the outer parts of the branches, causing the tips to discolor and lose needles while inner needles that weren’t as exposed during the freeze remain green.
In these cases, the only thing to do is wait and see. It is possible that in the spring, the buds that have already formed on the tips of those branches will still produce a new candle (the growth from which new needles emerge). We encourage you to wait to prune until you are certain a branch has died, as cutting a branch that has a healthy bud on it will result in no growth next season. You can gently pinch the buds on damaged branches to find out if they’re still healthy – a firm bud is a healthy one, while a dried out dead bud will crumble between your finger tips. In this case, as with sun scald, the best treatment is a good deep watering 2 times a month through the winter when possible.
Colorado Blue SpruceSpecies
The blue spruce, green spruce, white spruce, Colorado spruce, or Colorado blue spruce, with the scientific name Picea pungens, is a species of spruce tree. It is native to the Rocky Mountains of the United States.
Scientific name: Picea pungens
Biological rank: Species
Higher classification: Spruce
The names Colorado spruce, blue spruce and Colorado blue spruce tree all refer to the same magnificent tree—Pica pungens. Large specimens are imposing in the landscape because of their strong, architectural shape in the form of a pyramid and stiff, horizontal branches that form a dense canopy. The species grows up to 60 feet tall and looks best in open, arid landscapes, while smaller cultivars that grow 5 to 15 feet tall are right at home in lush gardens.
A slow-release fertilizer designed for trees helps keep your Colorado blue spruce healthy. Follow these guidelines when applying fertilizer:
Call your utility company before making holes in the soil around the tree so you don't hit any pipes or wires buried in the ground.
Because the tree's roots are fairly deep into the soil, you need to make small, 1- to 2-inch holes in the soil with an iron bar to a depth of 12 to 18 inches. The holes help ensure that the fertilizer reaches the roots.
Follow directions on the fertilizer label for your tree and mix the fertilizer with sand or compost to insert it into the holes.
Apply fertilizer once a year in the fall.
Damage From Pests
Colorado blue spruce is relatively resistant to pests, and they probably won't kill your tree, but they can do some damage. Look out for these insects:
Spider mites are the most serious pest your spruce may have, and they could affect the overall health of the tree. If the tree's needles turn yellow they may be infected. Examine the tree for the mites on the yellowed branches. If the tree is small, hose off the mites with a strong spray or use an insecticidal soap or a chemical insecticide for a large infestation. Follow the directions on the product.
Gall-forming insects come in a variety of types, but they all produce small bumps or growths that may look like miniature cones at the tips of branches. Galls will not harm your spruce.
Other pests that cause minimal amounts of damage include spruce budworm, spruce needle miner, pine needle scale and aphids.
Except for canker problems in the East, Colorado blue spruce doesn't suffer serious damage from diseases. If you live in that area, also plant a white fir (Albies concolor), which grows in zones 3 through 7.
These are the most typical diseases:
Canker turns needles brown before they drop off and produces white patches on branches that have been infected. To treat the disease, cut off infected branches and avoid overhead watering to keep the foliage of your tree dry. Sterilize your pruners after use to be sure you don't spread the disease to other trees.
Needle casts and rust both turn needles yellow or brown and cause them to drop off, but these diseases don't cause serious problems.
The hemlock tree is a coniferous evergreen tree. Information from the Arbor Day Foundation states there are three main types of hemlock tree: Western, mountain and Eastern. The Eastern hemlock is also known as Canadian hemlock, according to the University of Maine. Other names for the hemlock include hemlock spruce, weeping spruce, spruce pine and tanbark, according to Purdue University.
Hemlocks are large pyramid-shaped evergreens. Western hemlocks can achieve heights of 150 feet while Eastern hemlocks average 40 to 70 feet, but can get to 100 feet, according to the Arbor Day Foundation. Eastern varieties can be found in USDA hardiness zones 3 through 8; Western species are found in zone 6 but can adapt to other zones. The branches are pendulous, and cones are smaller than spruce or pine and more abundant. According to the USDA, the cones are short-stalked, brown with papery scales. Hemlock foliage does not change color in autumn but does have a light green to yellow color for new growth and a dark green for old growth, according to the University of Rhode Island. The bark is reddish-brown when the tree is young but darkens with age, says the USDA.
Hemlock trees are native to North America and can be found on both sides of the continent. The Arbor Day Foundation states that the Western hemlock can be found along the Pacific Northwest as far north as Alaska down through Canada. The USDA Forestry Service states that the Western hemlock can also be found through Washington, Oregon, Idaho, Montana and northwestern California. The Eastern hemlock, according to Purdue University, ranges from Ontario, Canada, down through Virginia and Alabama; it can also be found as far west as Michigan and Wisconsin.
Hemlocks grow wild in deep forests. Western hemlocks prefer dense shade and rocky soil, states the Arbor Day Foundation. The Canadian hemlock also is found on rocky ridges, hills and ravines. The Eastern hemlock is found along stream banks and where there are moist, cool beds, according to the University of Maine.
Hemlock trees are used for a variety of things. The Arbor Day Foundation states that the Western hemlock is an important part of the lumber industry, used for paneling, flooring and furniture. Hemlocks are also used for rayon yarns and tanning. Landscaping is another major use of hemlock trees, according to Ohio State University. The USDA also states that hemlocks are used in prevention of stream bank erosion. The University of Maine reports hemlock wood to be coarse, brittle when dry, strong and lightweight, but difficult to work with.
Throughout history hemlocks have been important. Tanning, basket-making, wool coloring, children's items and lining for pits were some of the uses Native Americans found for the wood, states the USDA. Other uses include poultices, liniments, windbreaks and structural support.