With vibrant flowers and soft leaves, tibouchina adds drama to containers and mixed borders by WAYNE WINTERROWD
IF, LIKE ME, YOU ARE A GARDENER “of a certain age,” you probably saw your first Tibouchina in a sunny parlor window in winter, its gaunt silhouette scantly furnished with large, felty leaves, and, perhaps, ornamented by one or two of its beautiful flowers. Or maybe you saw it on grandmothers wide front porch, still in its pot, but—one hopes—richer with flowers and leaves, set there to enjoy a summer vacation. Because, until about 10 years ago, there was no other tibouchina than those grown in large pots, primarily as house-plants. They are still excellent as such, but like so many tender perennials and shrubs, they have leaped from sunny windows to a brief freedom in the summer garden, their roots unbound to wiggle in the open soil. And so, just as with many other plants our grandmothers treasured for indoors, gardeners now think of them primarily as “annuals,” enjoyed for one season and then discarded at first frost.
There are many reasons for enjoying tibouchinas, but I am not sure their shape alone would be one. It is, frankly, gangly, made up usually of a central trunk and angular branches. But given its other assets, you can even come to love such a shape. It is a look offered by few other annuals or tender perennials and shrubs, and the leaves help out a lot. They are striking from a distance, carefully pleated ovals with sharp points; up close they are pretty, with thick velvety hairs that appear as tiny reddish bristles at the edges. They are lovely to touch. With maturity (or the onset of cool weather, or under drought conditions or any other stress) those leaves, born laterally along the stems at wide intervals, take on shades of vivid pumpkin and orange, offering an autumnal effect unmatched by any other tender shrub I can picture. (Well….cupheas can do that too, but never mind.) Leaves that have assumed this coloration cling to the plant for a surprisingly long time, but eventually they fall away, accounting for some of the nakedness of parlor plants.
All these things are lesser charms, however, because it is really for their flowers that tibouchinas are grown. Born in loose panicles, they consist of five slightly overlapping, broadly wedge-shaped petals, seemingly folded in the middle in a straight line across a cluster of purple-red stamens. Their color is one loved by all gardeners: a deep, rich purplish blue. It has a curious vibrancy, made up of one color brushed over another, as is seen in four o’clocks or some poppies. In tibouchinas case, the flowers are violet purple over red. Faint red stripes also emanate from the center outward— runways where bees land to visit the pollen-rich stamens. Each stamen terminates in a claw of a deep purplish black, giving the appearance that the whole flower has swallowed half a spider. Towards the end of summer, or during winter indoors, these flowers are even more magnificent, viewed against those orange-tinted leaves.
Tibouchinas belong in the family Melastomataceae, though they are the only ones of its 350 members much grown in gardens colder than USDA Zone 10. Natives of Brazil and Guiana, their curious name was taken whole cloth from the Guianan vernacular name for such plants. Two species are most commonly available to northern gardeners, Tibouchina urvilleana and T. organensis. One is an exact miniature of the other, though which one is the larger and which the smaller is often a little uncertain, since the two names seem mixed in the trade. You can tell the difference easily in the garden center, however, even when the plants are quite young. One will bear leaves around six inches long, and the leaves of the other will be half that. Flowers are also proportionately smaller, the larger species measuring four inches across, and the smaller seldom exceeding two. Your choice would depend on the effect you want. For the back of a border or in a large planter of mixed annuals and tender perennials, the taller would certainly be best. For the foreground of the border or for smaller containers, the smaller might be preferred. One doesn’t always have a choice, but if I were offered one, I would select the taller form almost always, for I have always liked its unapologetic ranginess, which makes it a sort of Ichibod Crane among tender shrubs grown as annuals.
Confusingly, the larger form of tibouchina is also offered under the name T. grandiflora, which suits it well enough. But that name properly belongs to a different species, rarely grown in northern gardens as a tender shrub, but magnificent in its own right and probably soon to be much more popular. It bears huge leaves, to 10 inches long and half as wide, pleated and downed like those of its cousins, but occuring much more thickly up and down the stems.
You’d grow it for its leaves alone, but its flowers are also beautiful, scarcely measuring more than an inch wide. They are also a rich, strong purple, but they are born in huge terminal panicles, perhaps as much as 16 inches long, with up to 30 flowers in a single panicle opening from midsummer to frost. It is stunning as a large tubbed specimen, but it could also be wonderful at the back of a perennial border, in a bay of shrubbery, or placed singly among ornamental grasses.
All tibouchinas are easy, requiring only moist, fertile, well-drained soil and full sun. They are excellent for containers, where they appreciate sharp drainage and the heat of the sun at their roots, but as many gardeners have recently discovered, they will also perform splendidly in the open ground. When in active growth, they respond dramatically to applications of water-soluble fertilizer every two weeks. Though generally open and rangy, they may be made more compact by frequent pinching when they are young.
You may wish to preserve your plants over winter. If they are in pots, they should be pruned back lightly, just enough to fit the window space available. If they are growing in the border, they should be root-and-top-pruned, potted in free-draining soil, and brought indoors or into a cool greenhouse before frost. In the darkest months of the year, they must be watered only when the soil surface is dry, and not fertilized until the light of spring returns and new growth begins to appear. In a sunny, cool parlor window (55-70°F) they should flower sparsely all winter long. Even a single flower, at Thanksgiving or Christmas, is a joy. H
For sources of plants featured in this article turn to page 76.