Strobilanthes callosa (Synonym: Carvia callosa (Nees) Bremek) is a shrub found mainly in the low lying hills of the Western Ghats, all along the west coast of India. Its standardized Hindi name is maruadona (मरुआदोना) which it is called in the state of Madhya Pradesh where it is also found. In the state of Maharashtra, in the Marathi language, and other local dialects and in the neighboring state of Karnataka, the shrub is locally known as karvi (कारवी), sometimes spelled in English as karvy. This shrub belongs to the genus Strobilanthes which was first scientifically described by Nees in the 19th century. The genus has around 350 species, of which at least 46 are found in India. Because most of these species show an unusual flowering behaviour, varying from annual to 16-year blooming cycles, there is often confusion on the national scale about which plant is flowering.
Description
It is a large shrub, sometimes attaining 6–20 ft in height and 21⁄2 inches in diameter and flowers between July and September. This plant is recognized for the fact that it takes nearly a decade for the bloom cycle to occur. Its leaves are home to several insects including caterpillars and snails which feed on it. The shrub has an interesting life cycle; It comes alive and green every year with the advent of monsoon, but once the rainy season is over, all that is left is dry and dead-looking stems. This pattern repeats itself for seven years, but in the eighth year the plant bursts into mass flowering. Plants that bloom at long intervals like Strobilanthes callosa are known as plietesials, the term plietesial has been used in reference to perennial monocarpic plants “of the kind most often met with in the Strobilanthinae” (a subtribe of Acanthaceae containing Strobilanthes and allied genera) that usually grow gregariously, flower simultaneously following a long interval, set seed, and die. Other commonly used expressions or terms which apply to part or all of the plietesial life history include gregarious flowering, mast seeding, and supra-annual synchronized semelparity (semelparity = monocarpy). In 1953 Sharfuddin Khan describing the plant in the former Hyderabad State wrote:
Botanical Name - Strobilanthes callosus Strobilanthes, Blume.; F.B.I. IV-429. S. callosus, Nees.; F.B.I. IV-451. Brandi's Ind. Trees, 500. Gamble's Ind. Timbers, 518. Vern. Karvi, Mar. A large shrub, sometimes attaining 6-20 ft. in height and 21⁄2 inches in diameter; branches often warted or scabrous-tubercled. Leaves opposite, 7 by 3 in., sometimes much larger, crenate, rough, conspicuously marked with five lines above, nerves 8-16 pair; petiole 2-3 in. Flowers in strobiliform spikes 1-4 in. long, often densely or laxly cymose; bracts 1/2 - 1 in. long, orbicular or elliptic. Calyx 1/2 in., in fruit often exceeding 3/4 in., sub-equally 5-lobed to the base; segments oblong, obtuse, softly hairy. Corolla tubular-ventricose, 11⁄2 in., glabrous without, very hairy within, deep blue; lobes 5, nearly equal, contorted in bud. Stamens 4; filaments hairy downwards; anthers blunt; not spurred at the base. Ovary 4-ovuled; style linear; stigma of one long linear-lanceolate branch the other minute. Capsule 3/4 by 1/3 in., seeds more than 1/3 in. long, thin, obovate, acute, densely shaggy with white inelastic adpressed hair, except on the large oblong areoles.
Tolerably common on the Kannad and Ajanta ghats in Aurangabad. In 'List of Trees, Shrubs, etc., of the Bombay Presidency,' Talbot remarks. "It covers large areas on the Konkan and N. Kanara ghats, and forms the undergrowth in many of the deciduous moist forests. Sometimes a very large shrub (30 ft., high and 21⁄2 in. in diameter). A general flowering takes place every seven or eight years. The white glabrous bracts become covered, after the flowering is over, with viscous strongly smelling hairs. The flowers vary in colour from purple-blue to pink. A general flowering of this species in N. Kanara, took place in Sept-Oct. 1887. The capsules ripen during the cold and hot seasons, and are elastically dehiscent, making a peculiar, almost continuous, noise during the shedding of the seeds in a forest of this species". In 1956 during the Reorganisation of the Indian States based along linguist lines, the above-mentioned state of Hyderabad was split up between Andhra Pradesh, Bombay state (later divided into states of Maharashtra and Gujarat in 1960 with the original portions of Hyderabad becoming part of the state of Maharashtra) and Karnataka.
Eight year bloom cycle and mass flowering The Strobilanthes callosa bush typically takes seven years to grow. It is only in its eighth year that it bursts into bloom. At that time the pink and white buds bear bright purple (purplish blue) flowers in a mass flowering which covers multiple forest areas with a colorful lavender blush of buds with a tinge of pink with its profusion of violet blooms, after this once in a lifetime mass flowering the bush finally dies out. The flowers are rich in pollen and nectar and attract a wide range of species of butterflies, birds and insects including honey bees and carpenter bees that come to feed on their nectar. Typically the lifespan of a single Strobilanthes callosa bloom lasts between 15 and 20 days and its mass blooming usually extends from mid-August to September-end. After the mass flowering, the shrub is covered with fruits which are dry by the next year. With the coming of the monsoon and the first rains in the next year, the dried fruits absorb moisture and burst open with a pop, the hillsides where Strobilanthes callosa grows are filled with these loud popping sounds of dried seed pods bursting open somewhat explosively dehiscing their seeds for dispersal and soon new plants germinate taking root in the wet forest floor.
Masting Some species of Strobilanthes including this one are examples of a mass seeding phenomenon termed as masting which can be defined as "synchronous production of seed at long intervals by a population of plants", strict masting only occurs in species that are monocarpic (or semelparous) -- individuals of the species only reproduce once during their lifetime, then die.
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