Plant Spotlight: Eastern Hemlocks

Tsuga canadensis

There are only nine total species of hemlocks in the world. Our Eastern Hemlocks are native and have a profound effect on our forests. They moderate the temperature of streams for our trout populations. Without hemlocks, the natural landscape can completely change. They are vital for both the canopy and understory. If they disappear, other trees like the birch will take over and change the environment.

Identification: Short, bright green needles with double white lines on the underside.

Features: 

  • Grows to about 100 ft tall
  • Shade and full sun tolerant, but prefers a little of both
  • Makes a great hedge for screening IF pruned regularly
  • Provides nesting for warblers

Major Pests:

Hemlock Woolly Adelgid

  • Invasive pest native to Japan, where it is a minor concern.
  • Lives under a white armored scale that can be found on the undersides of needles.
  • Sap-sucking creatures that cause needle death and dieback.
  • Becoming more cold tolerant the longer they live in New England.
  • Has two generations per year and causes major damage.
  • Needs to be controlled if not eradicated.

Hemlock Elongate Scale

  • Also accidentally introduced from Japan.
  • Does not kill hemlocks as quickly as the HWA.
  • Sucks vital nutrients from needles.
  • Causes yellowing on needles
  • Can be found alongside HWA.

Researchers are working tirelessly to eradicate these pests from New England and save our Easter Hemlocks. They have found that temps below zero Fahrenheit will kill them, but our milder winters are not being helpful in that discovery. Highly-selective pesticides and systemic solutions can provide protection for your hemlocks for up to two years. This will give our scientists the time they need to produce a much needed solution.

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