Frith Wood Nature Reserve contains 59 acres of ancient beech woodland on both sides of a ridge between the Slad and Painswick valleys, in the Cotswold Hills a few miles northeast of Stroud. The ridgetop is mostly treeless, occupied by a field; the woods cover the lower slopes, facing northwest - a generally moist and quite overgrown section - and southeast, where the land is drier and has less understory vegetation. The reserve falls within a larger Site of Special Scientific Interest (SSSI), Juniper Hill, The Frith and Bulls Cross, the hill being a westerly continuation of the north-facing side of the ridge, including a sizeable old quarry, while Bulls Cross is a patch of rough grassland to the east.
Like many arboreal nature reserves, Frith Wood is most attractive in autumn when the leaves are turning, and in spring, when large parts of the ground are covered with the flowers of bluebell and wild garlic. The majority of the other wildflowers are also common, though several rarer species are found here including wintergreen, white helleborine, broad-leaved helleborine, herb paris and bird's nest orchid.
The two halves of the woodland are crossed by various paths and old tracks, and the place is relatively popular, mostly with dog walkers. The land is steep, covering up to 150 feet of elevation, so the majority of the paths take diagonal courses across the slopes. Beech makes up about 80 percent of the woodland, and these trees are being selectively felled for timber, partly as many are approaching the end of their natural life; the woodland is semi-natural, with most of the original beech having been planted, from seed, in the early 1800s. Other species are ash, whitebeam, hazel, yew and holly.
Free parking is available at the Bulls Cross intersection (Slad Road and Yokehouse Lane), just beyond the northern tip of the reserve; from here a track heads southwest, past an information board and map, then divides, several times. Paths on the right lead to the northern section of the wood, and two form a 0.7 mile loop, while the others enter the more extensive southern section, crossing it on several levels. The best place for both bluebells and wild garlic seems to be the upper west end of the south woodland, where the ground is generally flatter, and part of this area was also once used for quarrying, as shown by several shallow, overgrown hollows. In the 18th century a cottage (Pan's Lodge) and garden was built towards the north side of the woods, overlooking Painswick Valley, and although long since removed, its location is shown by a group of non-native garden plants including mock orange, and is also marked by a bench with notice, alongside one of the paths. Some of the tracks pass through wider open areas, where wildflowers are more abundant.