Flora of the Prioksko-Terrasny Reserve is extremely diverse:
- 981 species of the vascular Embryophyta – herbaceous plants, bushes and trees;
- 133 species of mosses;
- 23 species of the Marchantiophyta;
- 625 species of the pileate fungus;
- 138 species of lichens.
In the reserve there are:
- 8 rare plants included in the Red List of Russia – the lady’s slipper orchid, the military orchid and others;
- 88 plants included in the Red List of the Moscow Region.
Forests cover about 93% of the area or 4598 hectares of the reserve.
The “pearl” of the reserve, the main reason why it was created, is so-called Oka Flora – areas of steppe vegetation surrounded by pine forests. In total there grow about 50 species of the Embryophyta, typical for meadow steppes. Scientists are still arguing about the origin of the steppe associations in the area located far to the north of the main natural habitat of these steppe species.
In the southern part of the reserve, there are unique plants, which are not typical for the Moscow Region:
- feather grass (Stipa pennata L.),
- Volga fescue (Festuca valesiaca Gaudin s. l.),
- Bieberstein tulip (Tulipa biebersteiniana Schult. et Schult. fil.),
- wedge larkspur (Delphinium cuneatum Stev. ex DC.),
- Gmelin alyssum (Alyssum gmelinii Jord.),
- Ruysch dragonhead (Dracocephalum ruyschiana L.),
- frutescent cherry (Cerasus fruticosa),
- serratula crowned (Serratula coronata L.),
- scorzonera purpurea (Scorzonera purpurea L.),
- Russian fritillary (Fritillaria ruthenica Wikstr.) and many other plants of the steppe zone.
Soddy-podzolic soils, typical for the reserve area, can be divided into three groups:
- brown earths,
- meadow cryptopodzols,
- meadow mesopodzols.
Gleyed meadow cryptopodzols develop near impervious beds.