EVERGREEN NEEDLE DROP

Broadleaved and needled evergreen plants shed their leaves. We’ve all seen the carpet of pine needles underneath a pine tree. This occurs as a result of both natural and environmental stresses. Each species of evergreen has their period of natural leaf drop or shed and this varies from one variety to the other.
Broadleaved evergreens (think Holly, Rhododendron, Euonymus or Southern Magnolia) usually shed their leaves in the summer or early fall. Juniper and Douglas fir needles will last for 10 or more years. Arborvitae and white pine will drop needles in the fall of their second year. Yew needles commonly will turn yellow and drop in their third year in the late spring or early summer. A Spruce tree can hold onto their needles for approximately 5-7 years. Eastern White Pine is one evergreen tree that is very noticeable as it loses its leaves in the fall. As stated above, the white pine sheds it’s needles in the fall of their second year, which leaves less growth at the tip of the branches to hide the needles that are shed making the fall needle shed seen more readily. The tree will appear particularly unhealthy when these yellow needles outnumber the green needles of the current season’s growth.
New needles will not regrow from the areas where they have dropped. However, new growth developing from terminal and lateral buds will mask the needle drop.
Natural needle drop occurs only on the inner needles. If your evergreen’s entire branches or needles/leaves at the tips of the branches are drying up and falling off, something else is happening.
Mites are often the culprit of non-seasonal needle drop. Generally, you will notice off-color needles becoming yellowish or brown. Sometimes, you will note the browning or yellowing starting in one particular area and gradually spreading throughout the plant. A light webbing is associated with heavy infestations. I good way to test for mites is to hold a sheet of white paper under a branch and shake or tap the branch. The mites will drop onto the paper where you can see them moving about. Aphids may also attack white pine needles. Bagworms are another common pest particularly on junipers and arborvitae.
Stress factors may intensify fall needle drop. Stress factors include drought, root damage, herbicide injury, disease, and, as addressed above, insect damage. The most common environmental factor being excessive soil moisture and drought. An excess of soluble salts in the environment such as occurs with the use of de-icing salts washing around the plant can also cause a large amount of dessication in some needled evergreens.
Some summer and fall leaf/needle drop is a natural condition varying in appearance depending upon weather conditions, plant health, and tree/plant species. Excessive needle/leaf drop at an inappropriate time may signal a cry for help. When in doubt, contact your nursery professionals or your County Extension Service for advice.