Pleroma kunthianum BM 4412
Tibouchina urvilleana Cogn.
Fl. Bras. (Martius) 14(3): 358.
Last time I looked, there was still one left, near the Cromlech. But what a pity such a beautiful plant has almost disappeared from Monserrate. Walter Oates records one from the small lawn below the chapel terrace in 1929.
This plant will naturalise in cool moist conditions. It is a weed in Hawaii, and in Madeira at Santo da Serra and other damp cool highlands. Sintra is too dry, here it is a cherished garden plant. It spreads by vegetative means, no viable seed is produced in cultivation. This explains why it is only invasive in damp conditions - roots from stem fragments. In habitat it actually grows in quite dry scrubby situations.
Infuriating nomenclatural history, far too many synonyms, often misidentified. Oates called it T. semidecandra. Hooker called it Pleroma Kunthianum. It was illustrated in Curtis's Botanical Magazine (4412) under this designation. (December of 1848) This species was introduced to Europe when raised from seeds received at Glasgow Botanic Garden (sent by Gardner when collecting in the Organ Mountains above 3000 ft.). Murray later sent seeds to Kew. Paxton in 1847 considered this to be a stove-shrub.
In 1841 Gardner took six wardian cases full of live plants by ship to England from Piedade, Brazil, one of these he refers to in a footnote as Pleroma Benthamiana. He had found it growing at Chapeo d'Uva in the Organ Mountains.
But there was a later introduction of a closely related species with much larger flowers, produced precociously on small plants. This too was illustrated: Pleroma macranthum BM 5721 (1868). "This magnificent plant ... the finest flowered of all Melastomaceae" Collected by M. Libon in the province of St. Catherine, and introduced by Linden from his nursery at Brussels. Mr Bull of Chelsea flowered it in April of 1868. Sometimes listed today is var. Floribunda, or var. Grandiflora. As we shall see this was actually Tibouchina urvilleana. As a superior plant it quickly displaced T. semidecandra, but the name stuck.
The mix up of names is still confusing today. Informed opinion (New York Botanic Garden) suggests that the Brazilian Tibouchina semidecandra is no longer in cultivation, plants grown in gardens are all Tibouchina urvilleana (synonymous with Lasiandra macrantha and Pleroma macrantha). Since this mix-up dates from at least the beginning of the twentieth century, it is almost certain that Oates's plants were Tibouchina urvilleana.
Pleroma Benthamianum, Pleroma macranthum, Pleroma splendens
Lasiandra Kunthiana, Lasiandra macrantha (still offered in some Portuguese nurseries under this name).
Tibouchina grandiflora, Tibouchina semidecandra
From Flora Brasiliensis vol. 14 part 3 p. 358
TIBOUCHINA URVILLEANA Cogn.
syn. Lasiandra Urvilleana DC
Pleroma vimineum Triana.
Habitat in insula S. Catharina : D'Urville, Guadichaud n. 242
Trivia: French naval officer Jules Sebastian Cesar Dumont d'Urville (1790-1842), was responsible for the purchase by the French government of a Greek statue found on the island of Milos: the Venus de Milo