Although the area of the National Park of Tzoumerka, Peristeri, and Arachthos Gorge has not been thoroughly studied in terms of its flora species, from past studies and scientific publications, we know that approximately 700 plant species grow in the area.

The slopes of Lakmos and Tzoumerka are characterized by a great variety of habitats that favor the growth of rare alpine plants and cliff plants. Barbarea sicula grows in wet meadows near streams, Centaurea affinis adorns rocky areas, and Cardamine raphanifolia is found in damp meadows and wet rocky areas near rivers on limestone or serpentinite.

In the clearings of forests and alpine meadows, plants such as sage, wild mint, tea, oregano, red lily, and many other plant species grow, which, when they bloom, create a mixture of aromas that characterize the mountainous regions.

Many well-known tree species, such as Kefallinia fir, black pine, oak trees, beech, wild cherry, hazelnut, ash tree, mulberry, plane trees, willows, etc., beautify the steep slopes of the mountains and the riverbanks.

From previous scientific data, we know that in the protected area, the total number of significant or endemic plant species amounts to 79. Out of these, 20 are endemic taxa of Greece, and the other 59 plant taxa grow only in the wider Balkan region. Endemic species are those that are found only in a specific geographical area and nowhere else in the world.

In the National Park, Achillea absinthoides grows, which is an endemic species of Southern Pindos, and Hieracium trikalense, which is endemic to Northern and Southern Pindos. Other examples of impressive or rare plants include the Thessalian fritillary (Fritillaria thessala), the alion (Allium parnassicum), the galio (Galium degenii), the orchids (Orchis pallens, Himantoglossum caprinum, etc.), and the rose (Rosa montana).

Also, particularly important is the presence of the rare species Solenanthus albanicus, which belongs to the Boraginaceae family and grows in the National Park. The global distribution of the species Solenanthus albanicus is highly limited, and for this reason, it is protected by European and international conventions (Annex II, Directive 92/43/EEC and Appendix I of the Convention on the Conservation of Wildlife and Natural Habitats, Bern Convention). The species is protected in Greece by Presidential Decree 67/81 (Government Gazette 23A/30-01-1981).