There are about four hundred species in the oak genus (Quercus) worldwide. Oak trees are majestic beauties and symbols of strength in many cultures. The oak is the national tree of not only the United States, but of England and Germany as well.
The extensive Oak Collection at The Morton Arboretum contains well-documented oak species and hybrids. There are 56 different kinds and over 200 plants that come from North America, Asia, and Europe. The collection is distributed across 12 acres on the East Side of the Arboretum. Botanic Gardens Conservation International determined in 2009 that it is the most significant botanic garden collection of oaks among 198 botanical institutions worldwide.
The site was originally oak-dominated upland forest during pre-settlement times. During the 1800s, forest products were harvested and the cleared areas were farmed. As evidence of this original landscape, many mature white oaks (Quercus alba) and bur oaks (Q. macrocarpa) commonly occur in the Oak Collection and throughout the Arboretum (including the Illinois Millennium Landmark Tree, predating Illinois' 1818 statehood).
Native species are particularly well represented. Seventeen species out of the total 21 Illinois native species are growing in the collection. Be sure to get a good look at the white oaks growing in the collection. The white oak is the Illinois state tree, and a symbol of Midwestern history and landscape. Another exciting and native oak species is the bur oak (Q. macrocarpa). Look for this oak's large acorns with their tough bristly caps, and spreading horizontal branches. Find the swamp white oak (Q. bicolor), and look at its leaves to figure out how it got its scientific name. Some new and interesting species added to the collection include a Turkey native, Hartwiss' oak (Quercus hartwissiana); a Chinese native, Liaotung oak (Quercus liaotungensis); and the Japanese native, gland bearing oak (Quercus serrata). This collection provides a great place to study the diversity of oaks.