Natural Setting for Hemlock Screening

“If Pennsylvanians were to select one tree as characteristic of our state, nothing would be better than Hemlock.” So wrote Dr. Joseph T. Rothrock, the “Father of Pennsylvania Forestry,” in 1896. In the mid 1800s Pennsylvania was number one in the country for lumber production and hemlock made up two thirds of that production. This majestic native not only provided wood for homes, but the bark is very high in tannin with is used in the tanning industry ever since it started in this country. On June 22, 1931 the hemlock was adopted as the state tree of Pennsylvania. The eastern hemlock is found in every county in Pennsylvania, but is most common in mountainous regions. The father of landscape gardening in America A. J. Downing felt the hemlock was the most picturesque and beautiful of the worlds evergreens. This plant has a very open conical shape with very dense foliage and branching down to the ground.

Alot of hemlocks planted in our Urbain areas today are very much in decline. There are two reasons for this. the first is when hemlocks were taken from there natural environment (growing along cool creeks and streams in very organic soils) and planted in urban areas were the top soil was striped and taken away. Then planted in hard packed clay soils that tend to dry out in the hot summer. This is not an endowment the hemlock can survive in. The second cause of decline is Hemlock woolly Adelgid, this is a small insect that looks like white cotton that attaches to the bark at the base of the needle. Damage is done when this insect inserts its piercing and sucking mouth into the base of the needle and removes fluids. This will cause reduction of plant health, Severe infestations will result in needle drop, die back and death of the tree. The best time to spray an insecticide to control this insect is September though October to try to kill as many adult females before overwintering. Also spring soil injections of a systemic insecticide will give you much longer control of this insect. Although these are very good controls for this insect in our ornamental, this insects continues to devastate our forests of Pennsylvania.