"The Future's so bright . . ."
For those of us who fancy Caladiums, and who are accustomed to the types we see in the big box stores, seeing a plant like the one pictured at right is sure to make one's eyes pop out of their sockets! Having grown this plant firsthand, I can state with certainty that the picture doesn't do the plant justice. The red color is incredibly intense and it is made even more so by the shiny leaf surface. This particular characteristic is amazingly unlike the Caladiums we all know and love. As a hybridizer myself, I'd love to know what parent(s) the Thai breeders used to come up with this plant and others like it. Until I saw this one, I had never seen a Caladium with a shiny leaf before.
Of course, not all of the new Thai Caladiums sport shiny leaves; as most of them have leaf textures that more closely approximate the kind of Caladium leaves that we are used to. However, one characteristic that these Thai plants do have in common, and which the regular Caladium plants do not have, is a thicker or heavier leaf substance. So far, most of the Thai varieties I have seen or grown have thicker leaves, and in some cases, much thicker leaves, than such familiar horticultural varieties as "White Christmas" or "Postman Joyner".
What's Going On?
As far as I have been able to determine, the origin of these new Caladiums is rooted in royalty. The Thai royal household, to be precise, had these plants bred for their exclusive enjoyment and not for the horticulture market at large. The story is that this breeding has been going on for a century or longer, with horticulture in the west completely unaware of it. Now that Thai Caladiums are out of the bag, as it were, we have a chance to see what a hundred years of secret royal breeding can produce.
The Thai Caladium breeders went in different directions than other Caladium breeders, apparently using some species or varieties that are unknown to Western horticulture. One species being used that is familiar to collectors is Caladium rubicundrum, a larger purple-leaved plant whose leaves also have lighter pinkish-purple spots. I've grown this plant myself and was anxious to try breeding with it, but my specimen failed to produce any pollen. Knowing what I know about genetics, I figure that the Thai breeders found or developed a fertile selection of C. rubicundrum and thus were able to use it in their breeding programs. Infertile plants can be made fertile by doubling their chromosomes (increasing ploidy). Such plants often have thicker leaves and are generally shorter and stockier than normal or diploid types. Interestingly, many of the Thai Caladiums have those characteristics, lending credence to my hypothesis.
An example of what I believe is a hybrid involving C. rubicundrum is pictured at left.
Easy as Thai?
My experience growing these plants has shown me that they are not as easy or carefree to grow as the usual Caladiums I have grown in the past. These require a bit more attention, and do not produce the large corms you might expect. They seem to be a favorite with aphids, which will infest the new emerging leaves and cause them to become distorted. Thai Caladiums do not like cold temperatures and will go dormant (or die) quickly when exposed to temperatures in the 40s and 30s. I was surprised to see their leaves show cold burn when tropical Alocasia plants nearby were undamaged. As a breeder, I am convinced that many of these new Thai Caladiums are at least tetraploid, and may be of even higher ploidy than that. This explains to me why many are smaller, have thicker leaves, and grow slower than the Caladiums we have grown for years. Some of these plants may be genetically predisposed to growing year round, as opposed to the seasonal growth we see with varieties like "White Christmas". You can get a good idea of the Thai Caladium varieties now available by visiting Asiatica Nursery.
All in all, I have found these plants to be very interesting and worth a try, As for their future with me, well, when I get the chance, I'll try mixing these up genetically with the Western types and see what I can come up with!Picture credits: LariAnn Garner, Aroidia Research