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Natural Browning of Evergreen Trees Interior foliage is turning brown—a normal occurrence.
Every fall our office is inundated with calls from clients concerned about brown foliage on their evergreen trees. They are convinced that the trees are dying. However, in most cases, there is nothing to be concerned about. What is happening is commonly called evergreen foliage drop, a natural shedding of the oldest foliage.
All trees and shrubs renew their foliage annually, producing new leaves in the spring and shedding the old leaves in the fall. The leaves of deciduous trees, like maples and oaks, are alive for just one growing season and then fall off usually in a blaze of color in the autumn. Foliage of evergreen trees lives from one to several years old, depending on the species. As new growth emerges in the spring, the older growth becomes shaded and its role in photosynthesis is diminished. Later in the year this inner or older foliage dies, turns a reddish brown and is shed, especially in the fall. This is a normal and annual occurrence.Seiridium Canker disease causing unnatural whole branch dieback.
In some evergreen species like pines, cedars, arborvitae and sequoia, this fall browning can take place rather suddenly. Sometimes this natural occurrence is hardly noticed, but this year it is especially noticeable, and people are concerned.
The natural foliage drop can be distinguished from disease by its uniform browning appearing evenly throughout the whole tree. Look around at other neighboring trees of the same species and you will observe similar symptoms. The shedding is confined to the innermost or oldest foliage or needles. The amount of foliage drop depends on the vigor of the tree, and of the preceding growing season especially in a drought year.
However, there are other serious disease problems that can cause foliage browning. Diseases cause symptoms and dieback that is a random pattern, scattered, not uniform in the tree. For example, we are experiencing a canker disease called Seiridium in incense cedars that causes a scattered (not uniform) but severe branch and foliage dieback. Large branches and attached foliage will turn brown and die usually in the lower half of the tree. Diseased branches should be removed for management of the disease.
So do not be concerned if the new, terminal or current year’s growth is green and vigorous, the health of the tree is not in jeopardy from natural foliage drop in evergreens.
The weeping Alaska cedar is a native conifer found growing from Alaska all the way down to Oregon and can achieve heights up to 80’. The Chamaecyparis nootkatensis ‘Pendula’ is a fine variety that forms an outstanding sculptural specimen.
The ‘Pendula’ cultivar is a slender, pyramidal, strongly weeping form that grows slowly to 35’ tall and 12’ wide over its lifespan. It is an excellent specimen tree that features a nodding central leader with graceful pendulant branches that sweep upwards at the end. The rich green foliage hangs like curtains from the branches, creating a graceful accent in the landscape.
The weeping Alaska cedar grows best in full sun and in acidic but well drained moist soil. It is tolerant of poor, heavy clay soils. Weeping cedars are drought tolerant once established in the landscape. This tree is relatively pest free. A valuable characteristic of this species is its high resistance to Phytophthora root rot. This means it can be used to replace other species that have succumbed to this insidious disease.
If you want an even narrower variety, try the ‘Green Arrow’. It grows 30’ tall but only 4’ wide.
Wood chips (fresh mulch, above) or composted mulch (below) are both good options for adding nutrients to the soil feeding your trees and shrubs.
A good tree ring of mulch should look more like a “donut” than a “volcano”. If possible, get rid of grass in the root zone area.
“To mulch or not to mulch?” It’s a question that’s often asked. However, for knowledgeable gardeners mulch is recognized as one of the most important cultural practices you can do for your plants. Maintaining your landscape plants in a healthy growing condition is important for your property value as well as the aesthetic benefit. A mulched landscape not only looks good, but also provides a wonderful environment for root growth. Mulching, coupled with the Collier Arbor Care Soil Health Care Program of organic fertilizer and Compost Tea, are the single best things you can do to care for your plants and your soil — and to keep your yard beautiful.
Benefits of Mulch
While mulching has a cost, its many benefits are well worth the investment. A mulch application can last for two to three years, but you may want to touch it up with small amounts each year. You will also be watering and weeding less and improving your soil at the same time.
Application is Important
Apply a two to four inch thick layer of mulch evenly out to the drip line of the tree or plant if possible. Leave a few inches of bare ground around the stem or trunk. Avoid applying mulch “volcanoes” or burying the trunk in mulch as this will cause the lower trunk to decay. The mulch ring should resemble a doughnut not a volcano. Once you have mulched, make sure your irrigation water penetrates and reaches the soil. Any water absorbed by the mulch will help in retaining soil moisture.
Did you know that trees grow better and have a thicker root system when the root zone is mulched versus a tree growing in a grassy area? If your tree had a say in the matter, mulch the entire root zone like a tree in the forest and get rid of the grass.
What kind of mulch should you use? There are organic and inorganic kinds. Inorganics include lava rocks, landscape fabrics and river rock, but these are not recommended for general use. If you choose inorganic mulches and later decide to remove it or plant into it you will have a big challenge.
Collier Arbor Care recommends organic mulches because of the wonderful benefits for soil improvement and root growth. There are two major types of organic mulches in our area: (1) Composted Mulch and (2) Fresh (non-composted) Mulch.
Composted mulch is the most desirable for amending and improving soil, but it does not suppress weeds well. Compost adds nutrients and promotes a healthy micro-biology in the soil. If you have a heavy clay soil, till in compost to help break it up.
Fresh Mulch such as bark or shredded mulch and arborist’s wood chips are the best for weed suppression. There are many grades of bark mulch from fine to coarse or made from hemlock or fir, just choose the color and texture you like the best. The fresh mulches have a minor issue with taking nitrogen from the soil which can easily be corrected by a small addition of an organic nitrogen fertilizer.
So which organic mulch should you use? We like using both! Put a half-inch thick layer of composted mulch down first then use a two to four-inch deep layer of bark mulch over the top.
Questions about your soil quality? Call today and let Collier Arbor Care help with a free Soil Health consultation!
Ecological Landscaping is a method of designing, building, and maintaining landscapes that considers the ecology of a site and creates a sustainable environment for the benefit of people, plants, insects and wildlife. Ecological landscaping strives to balance the building site with the natural environment. The sustainably built landscape will conserve natural resources, preserve biodiversity, and protect the environment. With proper design and maintenance, each component in the landscape; people, plants, water, soil, insects, and wildlife, will begin to interact together in a sustainable way.
The Five Steps to an Ecological Landscape
1 — Plan the Site
An eco-landscape is one that mimics a natural ecosystem with a diverse selection of large trees, smaller understory, shrubs, and groundcover.
2 — Protect Soil
3 — Planting Options
4 — Landscape Maintenance
5 — Water Usage
If you have questions about caring for a diverse landscape, please feel free to call or send an email.
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