Plant of the Month

 

Plant of the Month Archive

 

A Princess in Search of a Gardening Prince

 

To the Gardener, Tropicals are a revered group of plants that in their native near equatorial homelands are classified as a perennial or woody shrub.  However, in gardens with marked seasonality, they serve as exotic appearing annuals, providing bold textured foliage or dramatic floral displays that outshine the more traditional annual.  Come September, after several months of summer’s heat, Tropicals have truly hit their stride and the genus Tibouchina, commonly called Glory Bush or Princess Flower is no exception!

Tibouchina is a member of the Melastomataceae or Meadow Beauty Family and contains nearly 240 species native to Mexico, the Caribbean and northern portions of South America.  The family name is derived from the Greek Mela meaning black and Stoma for mouth, since eating fruits from this family evidently turns ones mouth dark purple!  Another distinguishing characteristic of this family, including Tibouchina is the foliage, which has 3-7 deeply incised veins that run longitudinally from the base of the leaf to the tip.  The stems are also typically square in cross section, a trait shared with Tibouchina!  The genus name of Tibouchina was first published in 1775 by the French botanist Jean Baptiste Christophore Fusée Aublet (1720-1778).  In 1762 he travelled to the town of Cayenne in French Guiana and amassed a large herbarium of regional plants.  A local species of this plant is known as Tibouch in Guyanese, which provided the inspiration for the botanical name.

Aside from the foliage and square stems, Tibouchina species are best known for their iridescent blue and blue-violet daisy-like flowers.  I was stunned by the flower color when I first saw a plant of Tibouchina urvilleana some 30 years ago and I remain so to this day!   This is a species native to the tropical rainforests of BrazilPOM and was originally named Lasiandra urvilleana in 1828 by Augustin Pyramus de Candolle (1778-1841).  The genus name is derived from the Greek Lásios for hairy and Andrós for male, and refers to the pubescence found on the stamens or male part of the flower!  The plant was properly categorized by the Belgian botanist Alfred Célestin Cogniaux (1841-1916) in 1885.  The species name honors the French Admiral, botanist and explorer Jules Sebastien Cesar Dumont D’Urville (1790-1842), with whom de Candolle collaborated on numerous occasions over the naming of new plant species.  However, it is doubtful that D’Urville discovered this plant, since his expeditions were mostly focused on regions in the Pacific and Antarctica.  This species does grow quickly and can reach 4’ tall by 2’ wide by September and ultimately 15’ tall by 10’ wide if it is over wintered indoors.  From June till frost, the five-petalled, 2-3” wide flowers open continuously for all to enjoy.  They also feature prominently protruding purple anthers, which in combination with the blue-violet petals is simply dazzling!  The lance-shaped foliage is 2-4” long by 1” wide and is lightly pubescent.  The mature growth is light green while the unfurling new growth is attractively blushed with red.  The stems are rather lax and can be trained into an espalier or worked up on a structure much like a vine.  Plants thrive best in full sun in soil that remains moist, but drains readily following a rainstorm, much as would be found in a rainforest.  Very similar in flower display is Tibouchina lepidota (picture above on right).  Slightly smaller in size and with stiffer stems, it is reportedly more floriferous with nearly identical appearing flowers.  The species epithet comes from the Greek lepis, meaning scale and refers to the plate-like bark that exfoliates on older specimens.  This species can be easily trained into a small tree or topiary.

If you need a plant with more strikingly bold foliage, consider Tibouchina heteromalla, otherwise known as Silverleaved Princess Flower.  Unfortunately, it is often sold as Tibouchina grandifolia, which creates much POMconfusion in the trade.  Unlike the previous two species, the foliage is larger, growing to 3-4” wide and long and is covered in silvery hairs that provides the inspiration for both the common and botanical name.  The leaves have 5 veins with the inner three not only very prominently incised, the area in-between these veins is distinctly raised or elevated (as seen in the image above).  The species is also native to Brazil and, once again was named by Cogniaux. The species name comes from the Greek Heteros meaning ‘another’ and Mallos meaning ‘wool’, referring to the different types of hairs present on the leaf.  Aside from the larger foliage, the blue 1-1½” diameter flowers are also presented in panicles with over 60 flowers per panicle!   Unlike the two former species, the flower petals overlap and the center of the flower is initially marked with orange and fading to white as the flowers age (see the image below at left).  As with it cousins, full sun and ample moisture provide the best growth and flowering.
All the species can also be overwintered in a brightly lit room that is maintained between 50-60 degrees.  Plants should be watered sparingly and fertilization stopped once the plants are brought inside, which will aid in inducing dormancy.  The plants will drop most of their leaves and need to be pruned and shaped come early April, when normal watering and fertilization should resume.  Plants can be placed outside typically the first or second week of May; place them in morning sun to get them re-acclimated to the stronger outdoor sunlight before they return to a sunny location.  For many of the species, the number of flowers produced actually increases as the plants age, making the task of over wintering the plants more enjoyable!  Tibouchina is a Tropical that most Gardeners and non-Gardeners alike have yet to try – it certainly is a Princess of a Flower in search of more gardening Princes!