The Kozara National Park is characterized by richness and diversity of plant life. Floristic diversity is caused by the orographic, edaphic and fitoclimatic factors, the plant-geographical position and historical development of the living world of the Kozara massif as well as of the very intense antropogenic impact at some localities .
In the relatively modest land area of 3,907.54 ha, an imposing biodiversity of the 865 plant species has been found. The total number consists of 117 fungi species, 11 lichens, 80 mosses and 657 species of higher (vascular) plants. Among the higher plants, there are 17 species of ferns, 114 types of trees (77 autochthonous and 37 allochthonous) and 526 herbaceous flowering plants. Autochthonous dendroflora in the Kozara National Park consists of 33 species of deciduous trees, 2 species of coniferous trees, 30 species of deciduous shrubs, 1 species of coniferous shrub, 2 woody vines and 9 sub-shrub species.
The most common deciduous tree species is beech (Fagus sylvatica), and the most common coniferous tree is fir (Abies alba). Beside dense deciduous and deciduous-coniferous forests, there are meadows and grasslands whose colourful grass and flowers complement the beauty of the landscape in the Park. In the respect of floral elements of flowering plants, the most numerous and equally present are species from Central European and Eurasian groups.
From the total number of plant species in the Park, there are 19 rare and endangered plant species:
- Northern whitestraw (Galium boreale),
- Holly (Ilex aquifolium),
- Cardamine (Cardamine bulbifera),
- Telekia (Telekia speciosa),
- Wild cyclamen (Cyclamen purpurascens),
- Wild lily (Lilium martagon),
- Lily of the valley (Convallaria majalis),
- Daphne (Daphne mezereum ),
- Liverwort (Hepatica nobilis),
- Orchid (Orchis morio),
- Ruscus (Ruscus hypoglossum)
- Sword-leaved Helleborine(Cephalanthera longifolia),
- Violet limpdore (Limodorum abortivum),
- Vicia (Vicia cassubica),
- Yew (Taxus baccata),
- Scabirosa ( Scabiosa cinerea),
- Figworts (Scrophularia scopolii),
- Carnation (Dianthus giganteus),
- Snowdrop (Galanthus nivalis).
A part of the floristic richness of the Kozara National Park is a number of herbs:
- St. Benedict’s herb (Geum urbanum),
- Herb Robert (Geranium robertianum),
- Eurasian smoketre (Cotinus coggygria),
- St. John's wort (Hypericum perforatum),
- Mallow (Malva moschata),
- European centaury (Centaurium erythraea),
- Lungwort (Pulmonaria officinalis),
- Betony (Stachys officinalis) ,
- Ribwort plantain (Plantago lanceolata)
- and many others.
Various edible plants and wild forest fruits should be added to the group of useful plants, such as:
- Pear (Pyrus piraster),
- Crab apple (Malus silvestris),
- Wild cherry (Cerasus avium),
- Blackthorn (Prunus spinosa),
- Pomegranate (Rosa canina),
- Dogwood (Cornus mas ),
- Strawberry (Fragaria vesca)
- and others.
There are various kinds of mushrooms, including a considerable number of edible and poisonous species in the area of the Kozara National Park. The most famous edible fungi species that can be seen when walking around Kozara are:
- Toadstool (Camarophyllus pratensis),
- Meadow mushroom (Agaricus campestris),
- Parasol mashroom (Macrolepiota procera),
- Chanterelle (Cantharellus cibarius),
- Safron milk-cap (Lactarius deterrimus)
- and others.