The park contains about 100 hectares of natural and semi natural woodlands and they are amongst the few native stands left in Co. Donegal.
The largest stretch is Mullangore Wood on the south eastern shore of Lough Veagh, although several remnants are to be found on the steep slopes of Glenveagh where the terrain is too precipitous for blanket bog growth.
Glenveagh is home to a mix of native and non-native trees, with the main species being sesile oak, downy birch, rowan, holly, hazel, yew and aspen. Scots pines are also a key feature having been planted as shelter belts around the lake shore.
The denser areas of woodland are rich in plants adapted to moist shady conditions. Mosses and ferns form lush green carpets on boulders and trees, and delicate filmy ferns sprout from the banks of moss. Golden leafed saxifrage and liverworts cover the wetter rocks and woodrush, wood sorrel and wood anemone abound on the woodland floor. Red deer find woodland plants particularly palatable and the woods are heavily grazed except where fences keep them out.
The woods are at their busiest in summer, when rising sap and fresh foliage provide plenty food for animals and insects. A variety of migrant birds, including the spotted flycatcher and chiffchaff arrive from Africa in mid-May, in time to exploit the summer abundance of insect life.
Among these is the wood warbler, a rare bird in Ireland but annual visitor to Glenveagh. Arriving in mid-May the male claims his territory and advertises to females by singing vigorously. The best way to locate one is to listen for its unique descending trill likened to the spinning of a coin on a plate. Other woodland birds include the colourful jay, the scarcer tree creeper as well as residents such as the chaffinch, song thrush and blue tit. Sparrowhawks are often heard too. Conifers planted in parts of the main glen harbour some typical pinewood birds including crossbill, siskin, gold crest and coal tit.
Badgers and foxes are important predators in the woods, though both are more commonly seen on the open heath. Their prey includes a little seen denizen of the woods, the long tailed field mouse. However both being opportunistic will take a wider variety of foods ranging from worms in the spring to blackberries in the autumn. Glenveagh is also home to stoats and pine martins, rarely seen but often captured on wildlife cameras by staff.
Several species of Bat emerge from hibernation by spring, and often roost in old buildings and woodlands in Glenveagh, making the most of insect prey which becomes abundant on warm nights. Leislers Bat – Ireland largest species, occurs in the woods, flying high above the trees and is more abundant in Ireland than the rest of Europe.