Characteristics that describes Biebrza's flora are: spruce dominated with large amounts of boreal species and glacial relicts such as Shrub Birch (Betula humilis), Narrow Small Reed (Calamagrostis stricta), String Sedge (Carex chordorrhiza), Crowberry (Empetrum nigrum), Labrador Tea (Ledum palustre), Cranberry (Vaccinium oxycoccos), Moor King (Pedicularis sceptrum-carolinum), Common Butterwort (Pinguicula vulgaris), Jacob's Ladder (Polemonium caeruleum) Downy Willow (Salix lapponum), Marsh Saxifrage (Saxifraga hirculus), Marsh Felwort (Swetia perennis),Cotton Deergrass (Trichophorum alpinum), Northen Bilberry (Vaccinium uliginosum). Of the more than 1000 vascular plants found in the Biebrza Valley, more than 900 of them exist in the Biebrza National Park. 90 vascular plant species are under strict protection and another 17 are only partly protected. 45 of these species are listed under the Red Data List of Endangered Vascular Plants in Poland!, these include Green Spleenwort (Asplenium viride), Variegated Horsetail (Equisetum variegatum), Great Sundew (Drosera anglica), Marsh Pennywort (Hydrocotyle vulgaris), Common Butterwort (Pinguicula vulgaris), Small Fleabane (Pulicaria vulgaris), Yarrow Broomrape (Orobanche purpurea), Marsh Felwort (Swetia perennis), Fritillary (Fritilaria meleagris), Iris (Iris aphylla) and 20 other orchid species including the Ladies Slipper (Cypripedium calceolus) with one of the most numerous populations in Poland!
List of vascular plants of the Biebrza Valley you can find at: http://www.zielonewrota.pl/flora/index.php