Collin Park Wood Nature Reserve protects a typical area of semi-natural, ancient woodland, used for deer hunting in medieval times and later coppiced for several centuries, latterly to provide charcoal for the local iron extraction industry. Visually the wood is unremarkable, with a flat floor and uniform trees, and its flora do not include any rare wildflowers, though the place is notable for the relative abundance of the otherwise uncommon wild service tree, which is one reason for its additional designation as a Site of Special Scientific Interest (SSSI), along with being a good example of damp, calcifuge woodland, i.e. containing trees which do not tolerate alkaline soils; sessile oak in this case. Other trees include small-leaved lime, ash, silver birch, aspen and field maple.
The wood sits on acidic, clayish ground, beside the floodplain of the River Leadon, and these conditions have resulted in a few heath-like plants growing here including common cow-wheat, foxglove and slender St John's-wort, in addition to the usual woodland species.
The SSSI ('Collinpark Wood') includes all of the wood (166 acres), but most is privately owned; the nature reserve covers the western quarter, excluding a permanent stream which adds interest to the northeast corner but including an industrial relic, a section of old rail bed - a cutting and an embankment - for a line intended to link the Forest of Dean to Worcester. The project was not completed due to lack of money, leaving the earthworks to become overgrown.
The nature reserve entrance, with parking space for several vehicles, is along a country lane (Brand Green Road) near Upleadon, 9 miles northwest of Gloucester. A path enters the woods, descending slightly to a junction at the start of a 0.7 mile loop, which to the west runs briefly alongside the railway cutting, the sides of which are up to ten feet high, and in the east crosses a slightly moister area, where a tiny stream flows during wetter times of the year. In the centre of this section of the woodland are two cleared areas, generally filled with ferns, while the majority of forest floor is quite densely colonised by bramble. Bluebells bloom in the spring but there do not seem to be any particularly impressive displays.