Old Furnace State Park contains a mixture of deciduous and evergreen forest trees that are typical in much of Eastern Connecticut. Stone walls and other relics show that farming and industrial activities have taken place, resulting in the second growth forest and man-made ponds that are visible today.
The most notable tree throughout the year is the Canadian (Eastern) hemlock. These majestic evergreen trees are found in many spots along the trail and the cliffs and can be identified by their flattened needles, small cones and dark cinnamon-brown bark. Unfortunately, the damage of a non-native insect, the hemlock woolly adelgid, is very evident in the park. The feeding activity of the hemlock woolly adelgid causes severe thinning and stress on the hemlocks. Other evergreen trees include two species of pine. The most common pine is the eastern white pine which bears soft blue-green needles and long narrow cones. A less common species is the pitch pine which grows in a few places along the edge of the cliff. The pitch pine has stiff, dark green needles and rounded cones which cling to the branches. Pitch pine is more common in coastal areas, but this tree is able to adapt to the poor growing conditions at the edge of the cliff. Deciduous forest trees throughout the park include various species of oak, birch, beech, maple and hickory. Common understory shrubs include witchhazel, blueberry and mountain laurel.
Several streams, wetlands and man-made ponds can be found along the trail. They contain an interesting mix of native plants including skunk cabbage, cattails and waterlilies. Unfortunately, several invasive plants have colonized the ponds, including phragmites and purple loosestrife. Phragmites is very easy to find because it looks like a large scraggly corn plant which has formed very dense groups along the shoreline.
Invasive plants are a concern at all of our ponds in Killingly. Once established they are very hard to eradicate and will crowd out the native vegetation. To help prevent the spread of invasive plants you should clean weeds off your boat when you exit the water and wash your boat when you get home. You can read more at the Connecticut Invasive Plant Working Group web site.