Elm (Species, Ulmus sp.; Family, Ulmaceae)
Elms occur naturally in the northern hemisphere temperate zones and at higher altitudes in the subtropics. Most are trees, some of which are very large and are deciduous and semi-deciduous. They are wind-pollinated and produce large amounts of pollen during September.
The planting of elms in Australia began in the first half of the 19th century when European settlers imported species from their former homelands. Owing to the demise of elms in the northern hemisphere as a result of the Dutch elm disease pandemic, the mature trees in Australia's parks and gardens are now regarded as amongst the most significant in the world. The pollen from Ulmus sp. does produce an allergic reaction in some people, and has been widely reported as a cause of hay fever in Europe and in North America.
Distribution of Dutch Elm (Atlas of Living Australia occurrence map)