Forest Snapshot March 2026

Forest Health

Winter burn is caused by a tree losing more water than it can take in. It usually happens during late winter warm-ups when conifers and broadleaf evergreens can begin transpiring, but the ground is still frozen or partially frozen. Wind exacerbates the condition by speeding water loss through transpiration. Winter-burned needles or leaves are brown or red-brown in color, and large areas of the crown can be affected. Usually, there are no long-term impacts. If your evergreens experience winter burn, check for viable buds on the branches, or check the branch health by scraping a small portion of the bark off the end of a branch. If viable buds are present, and the sapwood is still pale green and moist, the branch is still alive and will most likely recover. Extensive winter burn can be prevented in landscape trees by watering during late winter warm and windy days.

Invasive Species

Despite the cold temperatures, or actually because of them, winter is a great time of year to attack invasive shrubs. Whether you're using hand tools or contracting a forestry mower, cutting and removing invasive shrubs at this time of year minimizes wildlife impact, especially for birds that would likely be nesting in the shrubs during spring and summer. Another winter benefit to you: no ticks!

After cutting the shrubs down, the stumps can be treated with herbicide. When working in below-freezing temperatures, use a mixture of triclopyr ester and basal oil. Alternatively, the stumps could be allowed to regrow, and the sprouts treated with a foliar spray in early fall.

Native Species

Hello, spring! Migratory birds will soon be returning, filling the forest with songs, and while spring wildflowers bloom across the state. Flowering herbaceous plants that develop stems, leaves, and flowers early each spring and quickly bloom and set seeds before the overstory trees leaf out are called spring ephemerals. This is a common strategy for many understory species in deciduous forests: taking advantage of light passing through the canopy before being shaded out for the rest of the growing season. One species that you may find in rich woodlands is a native bleeding-heart, squirrel corn (Dicentra canadensis). A cluster of white heart-shaped flowers will develop along a central stem above blue-green leaves that are finely divided and resemble ferns. Each flower contains two sets of petals that spur or curve outwards at the tip. The name "Dicentra" means twice spur, referring to this feature.

The common name, squirrel corn, comes from underground tubers that look like pieces of corn, seen in the photo above, which attract mice and squirrels and aid in vegetative dispersal. Squirrel corn also reproduces sexually with seeds. After flowering, seeds develop in capsules that droop from the central stem. Each seed contains a fatty structure called an elaiosome, a high-value food source that is attractive to ants who carry and store the seeds underground, effectively planting the squirrel corn seeds in the perfect location for germination. Keep an eye out for squirrel corn this spring among the forest wildflowers.

Wildlife

In March, ruffed grouse will begin to mate. Males will be busy drumming—flapping their wings to create a drum-like sound that begins slowly, then speeds up so fast the individual beats aren't heard. Listen for ruffed grouse in young forests and forest openings.

Throughout the winter months, Pennsylvania insects are sheltered in their burrows or wooden cavities, protected from the frigid conditions. The insects around are either in larval or pupal form. The larvae of wood-boring or soil-dwelling beetles will consume materials in trees, downed logs, or soil. For some species, they'll be in this state for a few months and then emerge as adults when the conditions are right for them. Others may stay in this larval state for years! Solitary bees and wasps often overwinter in their pupal stage, having consumed the resources provisioned for them by their mothers and awaiting warmer conditions. Native bumble bees will overwinter as adult queens and enter a hibernating state known as diapause, waiting for conditions to be warm enough for them to begin looking for a nesting site and developing worker brood.

Notably, mourning cloak butterflies (Nymphalis antiopa L.) will overwinter as adults, living behind bark that is stripped away from tree trunks, under logs and leaf litter, or in cavities. With one of the longest life spans of any adult butterfly, mourning cloaks will survive the harsh winter in their hibernation and be one of the first butterflies to emerge in the spring. Come early March, be on the lookout for large queen bumble bees flying near the surface of the ground looking for nesting sites and ragged-looking mourning cloak butterflies looking to lay their eggs on elms, hawthorns, birches, and tulip poplars!