Evergreens can provide so many benefits to the landscape, but the most notable is that they are always green. When deciduous trees shed their leaves, they lose them all. As a result, what is left is only a stark, bare wooden skeleton. While this is visually dramatic, it is a bleak sight when days are short and nights are cold. Pines, junipers and other conifers can make a big difference — they look alive when most other plants appear dead to the inexperienced eye. Evergreens include more than conifers; African sumac also retains its foliage throughout the year.
Given that these trees keep their leaves all through the year, it can be surprising that they shed all the time. In fall, leaves of deciduous trees drop at once — sometimes after turning from green to other colors. When a canopy becomes bright orange, magenta or red it is a terrific display, but few of our local trees offer this kind of glorious sight. They begin looking dead before dropping onto the soil.
Evergreens drop their leaves, although it happens constantly. Beneath each pine, usually an Aleppo or a Mondale, is a layer of needles. This is mulch for the tree, moderating its soil moisture and temperature. These trees lose their foliage, a little at a time. Anyone who does not appreciate dead leaves on the mulch or lawn finds this an unwelcome sight.
The lower branches of pines turn brown over the course of time, but this is generally not an indication of disease, insect infestation or other problem. Because the foliage of many conifers is so dense, lower branches tend to be heavily shaded. With insufficient light, these leaves are unable to perform the necessary task of harvesting light and creating sugars through the process of photosynthesis. Rather than waste energy on unlit branches, the trees will let them die. They can then use their resources for growth and overall health.
One quick way to determine if a conifer is healthy is to look at it. Is the canopy sparser than you would expect? That is usually not a good sign. How many cones has it produced? Conifers create cones rather than fruits for sheltering their seeds. In fact, the formal name for conifers is "gymnosperms" which is taken from the Greek for "naked seeds".
When a plant experiences stress, it suffers. Whether due to improper soil conditions, drought, heat or other problem, it may begin to change its allocation of resources. Rather than growing new leaves, it will start producing many seed-containing cones. In this way, although the individual may die, the species as a whole will continue.
Fortunately, this does not indicate certain death. If the intrepid gardener can improve the conditions, and the tree has a healthy root system, it might come back to life. Adding compost, increasing water and applying a layer of mulch can work to improve its chances.
It will always lose leaves, but if it is healthy, a conifer can turn a dreary winter landscape into something a bit cheerier.
Dr. Angela O’Callaghan is the Social Horticulture Specialist for University of Nevada Cooperative Extension. Contact firstname.lastname@example.org or 702-257-5581.