Forests, which occupy a little bit more than 50 per cent of the reserve's area, dominate in the vegetation cover.  The main species is the arctic type of the pine, the Fries pine (Pinus sylvestris L.) or the Lapland pine (P. friesiana Wichura (P. lapponica (Fries ex C. Hartm.) Holmb.)).  A special feature of those forests is that they are open, have a low quality of locality and full of middle-aged, mature and overripe trees.  Nearly 60 per cent of the forests is older than 140 years.  The forests of Pasvik Reserve are among the most valuable in Murmansk region.

Pine forests are divided into two groups in the Paz River valley: moss pines and lichen pines.  Low shrub pine forests (with cowberries, black cowberries and bilberries), which occupy up to 60 per cent of the forest area, are wide spread in the well drained places.  Except low shrubs, bushy lichen can be found in the topsoil.  Lichen and green moss, green moss and low shrub pine forests are slightly less spread.  Fruticulose layer is presented by cowberries and bilberries, sometimes by ledum and bog bilberries.  Different species of Pleurozium and Hylocomium predominate among mosses.  Sphagnous pine forests are characterized by considerable thinning and depression; they can be found in the lowlands, between moraine hills, in the marine flat areas or other words in those places where there is loam in the soil.  Those overwetted forests occupy up to 30 per cent of the reserve's forest area.  Fruticulose and sphagnous associations, the dwarf birch, ledum and cotton grass are typical of the topsoil. Lichen pine forests are not that wide spread; they can be found in the uplands, in those places where the original rock or rough boulder moraine is a basis for shallow soil.  In such forests there is practically no undergrowth or underwood; they are very thin; lichens, which can occupy up to 45-85 per cent of the area, predominate in the topsoil.          

There was a total felling in some forests at the end of 19th century and at the beginning of 20th century.  In the middle of 20th century there were some minor selective cuttings.  There are traces of old fires in the whole area of the reserve; reforestation took place in a natural way there.  Three fires took place in the reserve after its foundation.  The total area of the burnt-out forests is 21 ha.    

There is no abundance of spruces (Picea obovata Ledeb.) in Pasvik Reserve.  Some depressed flowerbeds have been registered in the river valleys, in the central part close to the foot of Kalkupya Mountain.  Those communities are the northernmost natural spruce forests in Europe and in the world; they are like refuges and are of great importance for biodiversity conservation.  In the Paz River valley pine forests border on taiga; they are the northernmost coniferous forests in Europe.  To the east of the reserve the spruce is dominating species; it borders on the forest zone.  

The arctic type of the birch (Betula pubescens Erhr.) – the subarctic birch (B. subarctica N. I. Orlova) forms small-leaved forests and occupies up to 10 per cent of all reserve's forests.  On average birch forests are 70 years old.  Primary birch forests can be found on the riversides and by brooks; they are classified as a stream type and have a well developed grass and fruticulose layer.  On high shore slopes one can see green moss birch forests with cowberries and black cowberries, bilberries and black cowberries.  They have a well developed rowan and willow undergrowth.  Grassy birch forests can be found on the highlands which are up to 150-200 meters high.  Secondary birch forests grow in those places where there used to be cuttings or arable lands.  The birch forms the second forest level in mixed forests.  There is Betula pendula Roth but it does not make big associations; one can more often see its natural hybrids with the white birch.

There is abundance of aspens (Populus tremula L.) in the reserve and there are not many pure aspen forests; the species can be often found as an admixture in pine and birch forests.  As a rule the aspen grows on wet slopes or in mountainous areas where it forms green moss aspen forests with abundance of undergrowth.  In the Paz River valley one can see grassy aspen forests with lots of different grass, fern, turf (Chamaepericlymenum suecicum L.) and weak undergrowth.

In the central part of the reserve at the top and on the slopes of Kalkupya Mountain there is outcropping of crystal rocks in the form of rocky soil and placers.  Despite of being low (357 metres above sea level) altitudinal belts, which are typical of mountains, can be observed there.  There are low shrubs, green moss and lichen pine forests at the foot of the mountain; they are gradually replaced by mixed birch and pine forests at the top and pass into the crooked birch forest at a height of about 200 metres above sea level.  The peaks of Kalkupya Mountain are covered by forest tundra and dwarf birches as well as a mountain type of the white birch – Cherepanov birch (Betula czerepanovii N. I. Orlova (B. pubescens subsp. czerepanovii (N. I. Orlova) Hämet-Ahti, B. tortuosa auct.)) and pines «dressed in skirts».  Forest and tundra zones are passed into low shrub and lichen tundra and woodless areas.   Due to a big number of plant associations tundra looks special.    

Swamps occupy 25 per cent of the reserve's area and are incorporated into marine loam or clay deposits.  Pines grow in the upland swamps; sphagnum, low shrubs and cotton grass are typical of the soil cover.  Transitional swamps have a more homogeneous cover consisting of sedge and sphagnum; they are between moraine hills of the lowlands and occupy a small area.  Hollow places with running water are typical of complex or aapa- swamps.  Such swamps are abundant in Fennoskandia and sometimes they are called Lappish swamps.  A combination of chains and hollows is characteristic of aapa-swamps.  Chains are covered by low shrubs, moss and lichen, sometimes pines grow there; hollows consist of water-bearing peat.  One can often see lakes in the central part of such swamps.  Lowland swamps are typical of hollows.. slopes of hills.  Different grass species are typical of them.  Tussock bogs are typical of a forest tundra zone; they can be found on Menikk Island in the north of the reserve.  Tussocks can be up to 2 meters high; there are frost lens at the depth of 40-50 cm which do not melt till the middle of summer.     

Poium is of secondary origin as it appeared in the former arable lands; that area is not big, it occupies less than 1 per cent of the territory.  The meadows are gramineous and have high floristic diversity.  They can be found on the banks of the Paz River but mainly in the south of the reserve.   They are overgrown by birches and willows.  Periodical haymaking and cutting of young growth are needed to keep them.   

Vegetation of wetland sites is specific and formed by horsetail (Equisetum) quillwort (Isoetaceae), bur-reed (Sparganiaceae), pondweet (Potamogetonaceae), water plantain (Alismataceae), crowfoot (Rananculaceae), water starwort (Callitrichaceae), brushwood (Hippuridaceae ) and bladderwort (Lentibulariacea) families as well as different sedges (Carex).

Fauna of vascular plant and lichen is best investigated. Four hundred and eight species of vascular plants have been found in the reserve (including 494 species in its outskirts), 248 species of lichens and similar to them mushrooms (302 species including those in its outskirts) 106 species of the pileate fungus, 66 species of tree damaging mushrooms and 81 species of the muscoid. Algae are not studied.  Flora is better investigated with every passing year and the number of species is specified.