In the past the area of Warta Mouth National Park was primarily covered with carr forests that was mainly dominated by willow and ashe-alder carr. As a result of melioration works together with deforestation and pasture economy, formed wide-open ecosystems. Nowadays Park’s landscape is a mosaic of meadows, pastures, sedge and reed areas. The existing plant communities are typical for agriculturally developed valleys of big lowland rivers. To the original character of flora refer willow shrubs that formed secondarily by the Warta bed, communities of carr forest as well as single, grand willows and elms, probable remnants of the former carr forests.
Approximately 60 plant communities and about 500 species of vascular plants have been recorded so far. Among the species under full protection in Poland in the Park appear: early marsh orchid, european common twayblade, garden angelica, southern adderstongue, floating watermoss, and two species of crowfoot: common water-crowfoot and thread leaved water crowfoot and these partialy protected: white water-lily, yellow water lily, blackcurrant, alder buckthorn, guelder rose. In turn, plants rare in Poland and classified as regionaly endangered or extinctincting are: wild pea, marsh spurge, fen ragwort, smllflowered bittercress, fries’ pondweed, Cnidium dubium, Pennell’s speedwell.
The biggest areas of the Park are covered with rush communieties with dominating: reed canarygrass, reed mannagrass, slender tufted-sedge, great yellow cress.
Equally common are meadow herbaceous plants communieties that play a essential role in Park’s vegetation and encompass such species like: ragged robin, marsh marigold, hemp-agrimony, meadowsweet.
In canals and shallow oxbows lakes common are water plants communieties of a simple structure, composed of floating plants like: common duckweed, gibbous duckweed, greater duckweed. In deeper stagnant reservoirs develop groups of white water-lily and yellow water lily.
On the muddy water banks develop phytocenosis of annual plants. The most important species developing in this habitats are: brown galingale, marsh cudweed, toad rush, water-pepper, three-lobe beggarticks, helberd-leaved wild orache, red goosefoot.
In places with stable water conditions developed ash-alder carr, alder swamps and also osier clumps with dominating grey willow. On the frequently flooded terrain appear osiers with dominating almond leaved willow and common osier. Close to the Warta River bed pieces of carr forest developed.
On small hills appear grasses typical for sandy grounds like: gray hair grass, sea thift and maiden pink.
There is a tight forest complex in the northern part of the Park that covers about 80 hectares what is 1% of the whole Park’s surface. It is a habitat of a ash an alder carr in which some decades ago a forest economy was lead and planting of the preffered in that time black alder have been held.