This is the Arboretum's fundamental, and largest, plant collection. It encompasses trees, shrubs and subshrubs growing outdoors in the garden, both alone and in groups. The collection is universal in character. The majority of plant genera and species which are able to grow in the climate zone of the Arboretum have been, and continue to be, introduced into cultivation. In recent years, particular attention has been paid to obtaining new plants from natural populations and it is these which currently form the distinct majority of plants introduced. Natural taxa also have priority over cultivars. These constitute around 35% of the taxa being cultivated.
The collection's current status, as at April 2010:
The Arboretum's present dendrological collections number among the largest and most valuable in Poland. The garden's expanse allows for multiple cultivation of most taxa, giving a considerable variety and number of specimens originating from both the wild and garden origin. This offers a unique opportunity for the observation of, and research into, the plant population; moreover, it provides more than one specimen for the purpose, unlike many other botanical gardens and arboreta. It also permits for the better setting of seed. Several specimens of individual species are frequently planted in a variety of light and soil conditions, for the purpose of observing the differing reactions brought about by the diversity of habitats. The collections are situated on forest land, in a fertile, but acidic, luvic soil and are shielded by the tall pines, oaks, hornbeams and other trees among which they stand. These conditions determine the selection of species for the collections, among which, shade tolerant, acidophilic, forest species predominate. Xerophytic and sun-loving species are represented in smaller numbers, along with those preferring other soil conditions. The collections are planted in an ecological layout, namely, in line with their requirements as regards insulation, protection from the wind, humidity, soil type and so forth. They are not divided in accordance with geographical, systematic, morphological, or any other such criteria.
Within the overall framework of the dendrological collection, the Arboretum specialises, in particular, in several plant groups: