The outdoor rhododendron collection of the Experimental Rhododendron Breeding Nursery "Babīte" contains 102 wild rhododendron species and 345 cultivars (including 131 cultivars created in the University of Latvia). The hardiness and suitability of different species and cultivars is tested to fit the agro-climatic conditions in Latvia. The collection is used in research of genus Rhododendron, defining various physiological and biochemical processes and their changes in time of rhododendron ecological adaption, as well as in breeding of new and hardy outdoor rhododendron cultivars. Rhododendron seeds are obtained from botanical gardens, parks and collections all over the world: Bremen, Dresden, Bonn, Berlin, Munich – in Germany, Gothenburg – in Sweden, Antwerp – in Belgium, Amsterdam – in the Netherlands, Bergen – in Norway, Washington, Seattle – in the USA, Toronto – in Canada, Vladivostok, Irkutsk, Khabarovsk, Krasnoyarsk – in Russia, Minsk – in Belarus, Kiev – in Ukraine, Průhonice – in the Czech Republic, Vienna – in Austria, Edinburgh – in Scotland. The seeds of wild species are harvested on expeditions in the Far East, the Caucasus and the Carpathians. Seedlings are obtained from England, Germany, the Czech Republic, the USA, Belgium, the Netherlands and Finnish nurseries.