Uncarina grandidieri (Pedaliaceae)
Origin: Madagascar
Our featured plant this go-around is pretty unique. Coming from an odd family and an odd island, Uncarina looks like a cotton plant made out of velvet with large yellow felt petunias glued on it. The leaves, when crushed or even rubbed against, leave a pretty bad smell which kind of sticks to you. The plant blooms much of the year, but goes deciduous during our winters. The flowers are yellow with purple throats and are pollinated by beetles. Where pollination is successful, the plant sets very strange, very prickly fruits, covered in tiny hooks (ours does not set fruit). The plant is very popular among caudiciform enthusiasts.
Certain plants have a habit of forming a caudex, or swollen stem. Different species do this for different reasons, for some it’s a response to regular fires in their native habitat, for others it’s a mechanism for storing water in an otherwise parched desert. For whatever reason the caudex forms, its purpose remains the same; a way to store moisture and energy to support new growth, usually from the base of the plant. These plants tend to be referred to as “succulents,” and collectors of succulents typically tout their caudiciforms as the prizes of their collections. There are small blooming trees, such as the Uncarina, Adenium obesum (desert rose) or the Psedobombax (shaving brush tree) which can be kept short through pruning, resulting in a swelling of the base of the stem. There are spinier, more “cactus-looking” plants, such as the Pachypodiums (which should never be pruned) and Euphorbias which form caudices naturally, to hold water in arid climates. Whatever the species, and there are many which fit the bill, a caudiciform habit usually indicates a period of dormancy.
“Caudiciform” and “succulent” are both strange words, as neither has a strict botanical definition; rather, they refer more to a plant’s habit. Plants with fleshy leaves or stems which swell with stored water and become detumescent as the water is used up are generally referred to as “succulents.” These plants tend to live in environs which experience long periods of drought, and include the cacti, probably the most well-known group of succulents. We just finished a beautiful remodeling of our Succulent Garden here at the Gardens, where you can see our Uncarina grandidieri in full bloom, as well as many other caudiciform succulents. Just outside of our Conservatory is another fascinating display of adeniums and a cool caudiciform vine, Discorea mexicana, a species of yam which forms a caudex resembling a tortoise shell!
Text by David Troxell