Trunkline Magazine (Louisville Zoo) Trunkline Magazine: September 2017 | Page 22


A Tree as Old as Louisville

During this colorful time of year , many guests come to the Zoo not only to see our precious animal ambassadors but also to enjoy the autumn beauty of our accredited botanical garden . Traveling along the paths of the Gorilla Forest exhibit , you have probably walked beneath one of the most impressive specimens in our botanical collection . This tree , a massive bur oak , Quercus macrocarpa , casts a silent , sweeping presence over those lucky enough to pass under its branches .
The size of our bur oak denotes that this is an old tree , but how old is it ? This tree existed long before the Louisville Zoo opened in 1969 ; in fact , it was about 150 years old when the Zoo opened ! From measurements taken of the tree , it is estimated to be about 217 years old — meaning it would have first sprouted in the year 1800 . For reference , the city of Louisville was only 22 years old when this tree first germinated from an acorn . When the tree was just a sapling in 1808 , the famous ornithologist , John James Audubon , was watching the now extinct passenger pigeon blanket the sky in flocks of millions of birds .
Why is it called a bur oak ? Bur oaks produce very large acorns that are almost completely covered by the cap of the acorn and have a uniquely fringed edge on the acorn cap . The scientific name , Quercus macrocarpa , refers to two different points about the tree . The genus Quercus is Latin for “ oak tree ” and the species name macrocarpa comes from the Greek words macro meaning “ large ” and carpa meaning “ fruit ” in reference to the large acorn size .
Bur oaks grow naturally throughout much of the northcentral United States , the eastern Great Plains and southern Canada . Native to rich bottom land , bur oaks are tough and adaptable . They are cold hardy , tolerate drought and grow best in full sun . They are also more tolerant of urban conditions than most oaks . This oak species normally grows 70 – 80 ft . tall but can easily exceed 100 ft . or more . It has a tall broad-spreading , rounded crown that can grow to 80 ft . wide .
Take advantage of the temperate autumn weather to come enjoy the bright foliage at the Zoo this season . While you ’ re here , take a seat under the Louisville Zoo ’ s very own “ tree of life ” and bask in its shaded glory .
Did you know ?
When the Gorilla Forest exhibit was built in 2002 , precautions were taken on behalf of this magnificent tree . One of our first priorities was protecting the 200-year-old bur oak tree including adding lightning protection . Copper wire was run up the tree and then grounded by connecting it to copper ground rods inserted into the ground . This ensured electricity would be carried away from the tree .
22 • Louisville Zoo Trunkline • Fall 2017