The word arboretum refers to a collection or park of tree species. In the 1800s and early 1900s most self-respecting manor house owners had their own arboretums. Jakob Kavaleff (1870–1936), agronomist and owner of both the Haltiala and Niskala farms, established his own collection of exotic tree species on 2.2 hectares of land as a show park for the nursery he owned. Kavaleff was particularly fond of conifers and their special forms. He imported seeds and saplings from abroad and experimented with them in his nursery and arboretum.
The first trees were planted in 1905. After Kavaleff passed away, the arboretum gradually grew old and overgrown, and trees fell and died out. Ownership of the arboretum transferred to the City of Helsinki in 1961. The first thinnings were made in 1971 and 1972 to save individual trees of high value. The arboretum was granted nature protection status in 1984 in recognition of its rare trees and abundant birdlife. The latest maintenance and usage plan was approved in 2006. The planting of new saplings began after clearing in 2009.
Niskala arboretum is being developed to allow visitors to enjoy the park in its entirety or to study in detail the many individual tree species. As of 2016 over 750 different taxa (species and varieties) can be found in the arboretum. Visitors to the arboretum can find old plants and the remains of buildings that hint about its history. Hollow trees, fallen trunks and a wealth of tree and shrub species highlight the natural values, offering shelter and food for the park’s rich wildlife that includes mammals, birds, insects and fungi. The aim is to nurture a woodland garden in which the plants form a multilayered entity, from the bottom layer of herbaceous plants to the green canopy above.
The trees and shrubs that have been planted in the arboretum mostly correspond to the species and varieties that Jakob Kavaleff could have planted in his time. Although traditional arboreta usually feature only tree and shrub species, Niskala Arboretum also has cultivars of species that are specially named, bred and selected. The arboretum is divided into sections that are connected by a network of paths. These sections feature trees and shrubs from North America, East Asia, Europe and Japan that are suitable to the climate in Southern Finland. There are also separate sections for conifers and native Finnish species.
The oldest trees in the park, i.e. those planted by Jakob Kavaleff, are marked by illustrated signs. There is also a special tree path with information for children and adults alike. On the west side of the arboretum next to the orchard there are rest areas with picnic tables. The paths in the arboretum are not maintained in wintertime.
The City of Helsinki hopes that the arboretum will develop into a leading centre for dendrology in Finland amidst the attractive countryside just half-an-hour’s bus ride from the city centre.