China and Alabama – Botanical Brethren

Liriodendron tulipifera 'Aureo-marginata'
- Photo Credit: Birmingham Botanical Gardens

China and Alabama have more in common – botanically speaking – than most folks realize. Many of our favorite yard and garden plants are from China, such as Crape Myrtle (Lagerstroemia indica) and species of Camellia and Gardenia. These plants do quite well here because the southeastern climate is similar to much of China’s climate.

More intriguing is that the Southeast shares many plant genera (genus is the taxonomic level above species) with China. Both regions have species of azalea, rhododendron, maple, beech, and wildflowers such as ginseng, mayapple, and croomia. All total, there are about one-hundred plant genera shared between the two regions. The parallels are so profound that China’s and Alabama’s native floras are more similar to each other than either is to Europe and western North America, respectively. How did this unexpected pattern emerge?

Back in the Early Tertiary geologic period (65.5 – 1.8 million years ago), temperate forests covered the far northern lands of Asia, Europe, and North America. As new species evolved in one region, they would spread far-and-wide via the land-bridges frequently connecting the continents. In the Late Tertiary as Earth approached the Pleistocene’s ice ages (1.8 million years ago to 11,000 years ago), global temperatures dropped and ice blanketed the far north of these continents. This ended the easy inter-continental migrations of plant species. New species evolved as these temperate forest plants adapted to the new climate and local geology.

As Earth cooled further during the Pleistocene, northern forest species that survived were forced to spread southward to stay ahead of crushing glaciers and deadly winters. In both eastern Asia and eastern North America, north-south trending mountains provided an easy path for the spreading species. The Appalachians guided hundreds of these plants all the way down to central Alabama where many still reside. Not so in Europe, where the east-west trending Himalayas blocked the southward migration of plants, and without an easy path to the warmer south many species went extinct. During this same time, drought caused widespread extinctions in western North America. As a result, Alabama’s flora is more similar to China’s flora that it is to Arizona’s flora.

You can see some of these remarkable parallels between China and Alabama at The Gardens. In particular, look for matching genera between the Barber Alabama Woodlands and the adjacent garden across the paved trail between them. You can also easily look up on the internet the distributions of your favorite plant genera and see if any of them share the China-Alabama connection.

There is a dark side to this connection, too. Many of our worst exotic invasive species – non-native organisms that invade natural ecosystems and displace native species – are Chinese species well-suited to our environment, including Chinese Privet (Ligustrum sinense), Chinaberrytree (Melia azedarach), Chinese Wisteria (Wisteria sinensis), and Chinese Lespedeza (Lespedeza cuneata).

– Scot Duncan