The past few years have taken a toll on the health of hemlocks throughout the landscape. Several growing seasons plagued by drought have brought about explosions in aggressive scale insect populations. When coupled with other perennial problems such as woolly adelgid and several species of mites, declining hemlocks have become one of the most common issues encountered by both homeowners and professionals.
With wild temperature and rainfall fluctuations, threaten your hemlocks' health throughout the year.
In 2017, Massachusetts finally saw average amounts of rainfall that brought some parts of the region out of the grip of extreme drought. A palpable sense of relief was felt by all. Unfortunately, that false sense of security gave way to wild temperature fluctuations in the winter, which once again threatened the health of hemlocks. When winter temperatures warm up quickly, evergreen plants lose moisture through their needles and leaves that cannot be replaced while the ground remains frozen. Conversely, extremely cold temperatures can cause damage by actually freezing plant cells, like frostbite, and lead to additional dieback.
Trees already experiencing stress (such as exposure to road salt, exposure to strong winds and reflected sunlight, disturbance of the root zone, etc.) are affected more seriously. This added stress causes foliage to turn alarming shades of orange and brown. In the worst cases, it can shut down an entire tree, and in mild cases might only damage the newest growth. Serious damage raises major health concerns for a species like hemlocks that contains much of its energy in the needles.
So what can I do to protect my hemlocks?
An annual assessment by a certified arborist is a requirement for any effective maintenance strategy by hemlock owners. Remaining vigilant about the health of your hemlock is paramount in protecting your trees from the unpredictable effects of a changing climate. Supplemental watering is necessary during periods of drought, and timely applications of registered pesticides will help eliminate problem insects such as hemlock elongate scale and fiorina scale. Avoid high nitrogen fertilizers that will exacerbate these insect issues.