Bartlett on Gardening: Gemini 1--Are We Related?

We are in the season of Gemini, which means twins in Latin. The mythological twins, Castor and Pollux, were placed in their constellation by Zeus so that they would never be separated by death.

This seems like a fitting time to look at some plants that share a name. Are they twins, members of the same clan sharing the name? Or are gardeners confused about plant identity? And does it really matter?

Exhibit A is elephant’s ear. I find these large tropical foliage plants irresistible. I have bought them knowing they were annuals. I have also found some to be perennial. Are these really all the same thing?

Alocasia (left) is a shade-loving tropical from South and Southeast Asia. It has enormous, interesting, upright leaves, making it a terrific accent plant. Some Alocasia plants may be hardy in Zone 10, but they are annual here in Zone 7. Alocasia’s common name is elephant’s ear.

Colocasia, or taro (right), is native to swampy, tropical areas of Asia where it is grown as a food staple. Some cultivars are hardy to Zone 7. These plants have showy albeit shorter foliage. They are also called elephant’s ear.

Thus, when selecting an elephant’s ear, I check the plant label closely to see if I am buying a summer romance or a long-term resident.

​​Exhibit B is plumbago. I know plumbago (Ceratostigma plumbaginoides) as a spreading ground cover for all degrees of shade. In late summer it produces brilliant blue flowers that last into autumn, when the foliage turns red.

Then I found a lovely sky-blue-flowering, sun-loving annual in a garden center last year. It was labeled “plumbago”. Could there be two plants with the same name?

The sun-loving plumbago (Plumbago auriculata) (right) is a tender perennial native to South Africa. Its common name is Cape leadwort because it was thought to cure lead poisoning. It turns out that my ground cover (above) is sometimes classified as Plumbago larpentiae. Although not twins, the two plants are members of the same botanical clan.

Next week, we will look at a curious case of mistaken identity.

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