Here, plants are grouped by geographic regions. You will discover plants from Madagascar, Africa, the Canary Islands, South America, and the deserts of North America.
An island off the east coast of Africa, Madagascar's isolation from the mainland has facilitated the evolution of species found nowhere else on Earth. Our collection is one of the largest in the United States. Whenever we could not obtain specimen plants from other collections, we started plants from seed sent directly from Madagascar. Familiar "friends" such as Euphorbia milii (Crown of Thorns) and Catharanthus roseus (Madagascar periwinkle) will greet you as well as bizarre trees (Operculacaria) and shrubs (Alluaudia and Pachypodium) that shed their leaves during drought or store water in large swollen stems and roots called caudexes. Other unique plant categories or taxa in the collection include Didierea, Adenia, Cyphostemma, Uncarina, and rare species of Euphorbia.
As the succulents of North America go dormant for the winter, the Aloes of Africa begin to bloom. Overhead you will see tall columnar Euphorbias and caudex-type plants or caudiciforms, such as Namibian grape (Cyphostemma juttae). At your feet are varieties of Lithops (living stones) that store water in leaves that mimic small stones and bulbs, including the fall-blooming white paintbrush (Haemanthus). Perhaps the most intriguing specimen of all is Welwitschia mirabilis from southwest Africa. The plant's long taproot allows its stiff leathery leaves to survive for decades. An equally intriguing ancient plant is the cycad, Encephalartos ferox, a relative of our familiar conifers.
Featured on a small "island" along the walk is the splendid Dracaena draco, the Dragon Tree. It was so named because its red sap was once marketed as "dragon's blood" during medieval times. This species often grows to immense size and can be well over 1,000 years old.
In the shade of date palms, you will find a small pool with aquatic plants, providing a psychological respite from the heat of summer. By the shore is our arid ethnobotany garden with plants important to arid agriculture, especially chile peppers. Chiles were one of the earliest plants to be cultivated in the New World and today are among the top 75 most consumed plants in the world.
We tend to think of tropical rainforests when we think of South America rather than deserts, but countries such as Argentina, Chile, Bolivia, Brazil, Peru and Colombia do indeed have extensive dry areas. Some of these deserts are at high elevations that experience intense light levels. The cactus family is well represented, and you will find adaptations that include white wool, dense spines and columnar growth.
The deserts of North America--the Sonoran, Mohave and Chihuahuan--are rich floristically, in both species diversity and growth forms. Our collection reflects this diversity in its cacti such as Opuntia and Golden Barrel with succulent stems, heavy spines, and wooly hairs; the tall columnar Cereus and Saguaro cacti; the deciduous shrubs such as Ocotillo and Creosote Bush; and the curious caudex types, with their large swollen stems and roots, such as Bursera and Jatropha.
Mitchell Park Horticultural Conservatory (The Domes)
524 S. Layton Blvd., Milwaukee, WI 53215