The Adenium — better known as the desert rose — is related to the plumeria, evident by the look of its blossoms and its milky sap.
The first types planted here produced pink flowers, but we now have deep magentas, whites and multicolored varieties in our gardens. Amazing horticulturists in Thailand are producing new varieties in striking tones, some even with double petals. These also are turning up in Hawaii gardens.
Local growers are even making their own cross-pollinated varieties, just as with plumeria.
The Adenium — of the Apocynaceae plant family — is native to Africa and the Arabian Peninsula — some east-African names include impala lily and Sabi star, according to a fabulous 1975 newspaper article by the late, great plantsman, Horace Clay, shared with me by Clyde Imada of the Bishop Museum.
The earliest herbarium specimen of Adenium was collected here in May 1954 at Foster Botanical Garden by Harold Lyon, according to Imada’s information.
Happy in pots, Adeniums bloom often and the flowers are long-lasting. The plants are also interesting with their bulbous, fat-bottomed, water-storing trunks — also called caudices.
They like good well-drained soil. I like to mix some nice garden soil with coarse cinder and potting mix in a 1:1:1 ratio.
The Adenium is perfect for a sunny lanai, and seems to bloom better when kept in a pot. I have seen very large specimens kept in pots, growing and blooming prolifically for years, transplanted to larger pots as needed. It also makes an epic bonsai.
After Adenium flowers are pollinated, a two-pronged seed pod — which looks like a plumeria pod — develops over several months. Inside the mature brown pods are straw-colored seeds with golden gossamer wings. Watch the pods and capture the seeds before they blow away! Grow them in a pot of well-drained planting media and see what colors emerge.
The plant lover might try cross-pollinating these plants, cultivating new varieties from seed. They also grow from cuttings and can be grafted, but plants grown from seeds develop a more interesting, fatter trunk.
We planted the Adenium in our botanic gardens before 1997, with many placed in the hot, sunny, well-drained tuff soil at Koko Crater Botanical Garden. We planted them in the African section, on steep hillsides with attractive rock formations. They look fabulous growing near the equally fat-bottomed baobabs and the African species of Moringa.
Today, many striking colors grow, and they make the garden interesting with that pop of color, a contrast to the general colors of silver and gray that many drought-tolerant plants display.
Some Adenium will be for sale at the upcoming Unthirsty Plant Opens in a new tabSale Opens in a new tab, Aug. 4 at the Halawa Xeriscape Garden. Adeniums grow there in the landscaped dry river bed.
Heidi Bornhorst is a sustainable landscape consultant specializing in native, xeric and edible gardens. Reach her at heidibornhorst@gmail.com.
