Evergreen is not the same as forever-green. Like maples and oaks, individual leaves or needles shed from pines and arborvitae yearly. Even though the show may not be the same as our fall foliage stars, to a gardener who just discovered their well-cared for trees suddenly dropping their needles, it can be very startling. Rest assured there is no cause for alarm since leaf and needle drop occur as a natural part of the yearly growth cycle for many so called evergreens.
A tree or shrub is named an evergreen if their leaves persist more than one year before falling. In our part of the U.S., that includes conifers like pine, arborvitae, spruce, and juniper. These plants are also called narrow-leaved evergreens. The needles of narrow-leaved evergreens shed in late summer or early autumn. The natural yellowing of older needles, those towards the center of the tree, occurs uniformly from the top of the tree to the bottom. Needles at the tip of each branch (the younger needles) stay green. Since the younger needles are still green and healthy in appearance, then you can be certain this is normal and nothing needs to be done.
New needles are added every year, so there is always an overlap between green needles and those due to fall. In most years, gardeners may never notice this leaf drop as it occurs gradually over a long period of time. In some years natural needle drop occurs in a short period of time making for a striking display but, some may fear they are losing the tree. This more rapid leaf drop is triggered by weather and/or other stress factors.
Each species of evergreen tends to keep its needles for a defined length of time. Eastern white pine holds its leaves for three years. But during a year with stressing weather conditions, it may only retain the current season’s growth, leaving the second and third year needles to turn yellow. When this happens, the tree can appear unhealthy as the yellowed needles outnumber the current season’s green ones. Some other pines may hold their needles for 5 or more years.
Spruce generally hold needles longer than pine, up to 7 years but specific junipers may last 10 years or more. Yew needles turn yellow and drop in the late spring or early summer instead of fall. They typically drop 3 year old needles, but yews growing in heavy clay may exhibit prominent yellow needles in the spring. Although they are not evergreens, a few conifers (bald cypress, dawn redwood) drop their needles every year. The following lists commonly grown conifers and the number of years they hold their leaves.
Commonly grown conifers and the number of years they hold their leaves:
Bald Cypres 1 yr
Dawn Redwood 1 yr
Arborvitae 2 yrs.
Eastern white pine 3 yrs
Yew 3 yrs
Jack pine 2 to 4 yrs
Scotch pine 3 yrs
Lacebark pine 3 yrs
Austrian pine 3 yrs
Mugo pine 5 yrs
Spruce 5 to 7 yrs
Juniper 10 yrs or more
A few broad-leaved plants like southern magnolia, boxwood, and holly are also called evergreens. And just like their needled cousins, they also experience leaf drop. Rhododendron and euonymus may shed their older leaves in summer or early fall following the maturing of the current season’s growth. Southern magnolia and holly drop many of their oldest leaves as new growth begins in the spring. But like the needled evergreens, the leaves on the branch tips remain healthy and green.
Even though it is unnecessary or even possible to control or reduce natural needle drop, there are some situations that can make it more pronounced.
Trees experiencing root stress due to less than optimal growing conditions may have more noticeable needle discoloration. Extended dry periods, poorly drained sites, and heavy clay soils accentuate root stress to pines. Keep your evergreens healthy by following good cultural practices: irrigating evergreens during dry periods; maintaining proper soil fertility and pH, and controlling pest problems before they cause damage.
Even though needle drop is natural, don’t assume every time branches or needles turn yellow or brown that it’s just a natural shedding. If more than just the oldest needles are turning brown, then something else is happening. Plants should be inspected for fungal leaf spots, spider mites, aphids and other potential pest problems. Drought, too much soil moisture, or air pollution can also cause needles to turn yellow or brown. Examine your plants carefully. So long as the newest needles or leaves at the tip of the branches are green and healthy, relax and enjoy the fall display of your backyard evergreens.
Educational programs of the University of Kentucky Cooperative Extension Service serve all people regardless of race, color, age, sex, religion, disability or national origin.
— Kelly Jackson, Christian County Extension Agent
