Pajasen (Ailanthus altissima) brzorastuće je listopadno stablo podrijetlom iz Kine, visine do 35 m. Maksimalna prilagodljivost uvjetima okoliša u kojem raste čini ga oportunističkom i kozmopolitskom vrstom koja je proširena na svim kontinentima osim na Antartici. U Europu je unesen 1740 g., kao ukrasna biljka. U Hrvatskoj se, zbog brzog rasta i razgranatoga korijenova sustava, na nekim mjestima sadio kao vrsta koja sanira klizišta, a danas je rasprostranjen duž cijele zemlje. Veću agresivnost pokazuje u obalnom dijelu Hrvatske uključujući i posebno osjetljive otoke, parkove prirode i nacionalne parkove u kojima agresivnim širenjem potiskuje autohtone vrste, nepovratno mijenja izgled krajolika te narušava stabilnost ekosustava nanoseći im neprocjenjivu štetu. Suzbijanje pajasena vrlo je zahtjevno i za uspjeh je potrebna kombinacija nekoliko različitih metoda.Tree of heaven (Ailanthus altissima (Mill.) Swingle) is a fast-growing deciduous tree originating from China, up to 35m in height. Its maximum adaptability to different environmental conditions in which it grows, makes it opportunistic and cosmopolitan species that is present on every continent except Antarctica. It was imported in Europe in 1740 as an ornamental species. Due to its rapid growth and branched root system, on some locations in Croatia it was planted as an erosion preventing species. Nowadays it is widespread throughout the entire country. It is shown to be more aggressive in the Croatian coastal area, including the islands which are particularly vulnerable, but also nature parks and national parks, in which its aggressive expansion suppresses the native species, irreversibly changing the landscape and affecting the stability of ecosystems while inflicting enormous and incalculable damage. Control of the tree of heaven is very demanding and in order to be successful, a combination of several different methods is required
