A biological and ecological phenomenon, where the appearance of mass blooming of herbs around the Maussakele Reservoir near Maskeliya was reported in recent newspapers. The Sunday Observer (Spectrum) of April 30, 2017 published an article titled, “Blossoming in the reservoir bed of Maussekelle” by Mahil Wijesinghe. I visited this spot on May 1, with my family and some friends, to observe this phenomenon of mass flowering and identify what these flowers are. An area of several hectares on the dried-up reservoir bottom was an eye-catching field of herbs erupting with very showy purple-pink flowers, a mimic of a vast colourful floral cloud over a green background. The location lies in the vicinity of the age-old Hindu temple of the old Maskeliya town that is normally submerged, but becomes exposed when the reservoir’s water level drops very low during long droughts. The present mass blooming has begun about two months ago, it was reported.
What flowers are they?
A visit there, with my family and friends, on the first day of May and a close examination of this curious sight revealed that one species, known as Spider Flower dominates the scene. Botanically it is Cleome speciosa, classified in the family of Cleomaceae, closely related to the mustard family (Brassicaceae). Strangely, it is not a native species in Sri Lanka, but an introduced flowering herb popularly seen as a flower bed species, especially, in the mid and upcountry. Almost invariably it can be seen in most gardens in Nuwara Eliya and Hakgala areas and often in Kandy, including the Peradeniya Botanical Gardens.
However, it is not normally seen as an escape from cultivation, occurring as a weedy species (naturalized) and this is possibly because of its requirement of human attention and care for establishment in a reasonable population.
Unlike in a cultivated field where a single species thrives (monoculture) due to human involvement, nature promotes the establishment of other species, although in small populations. Following this law of nature, the Spider Flower population at Maussakele is also not alone, but accompanied by several other herbaceous species, e.g. Floss Flower (Ageratum haustonianum), Willow Primrose (Ludwigiadecurrens), “Muda-mahana” (Sphaeranthus) and “Hulan-tala” (Blumealycopersicifolia) etc. that add more colour to these meadows. However, they occur close to the ground, more or less occupying gaps left by the vigourously growing Spider Flower.
Spider Flower and its global distribution
The plant is an annual herb (living one year or less) which grows, under ideal conditions, to about breast height (up to 1.5 meters). The main stem is erect and stout with short spines and often with 1-2 branches producing palmate (palm-like leaves, each with normally five segments). The whole plant is somewhat sticky as it is covered with glandular hair. The leaves are eaten, often as a mixed leaf vegetable, especially, in several African countries. Large and showy flowers are borne on terminal inflorescences (racemes) mimicking a floral flare. Most plants bear purple-pink flowers while about 5% is white flowered. Normally, each plant can produce 150-200 flowers and an equal number of long spindle shaped fruits (capsules).
Each fruit is up to 8 mm long, borne on a very long stalk (nearly 10 cm) and produces about 70-125 seeds which are greyish and mustard-like. Fruits split open when mature, especially, in dry weather to liberate the seeds. Therefore, it can be estimated that a fully grown plant can produce 10 – 25 thousand seeds of which a certain percentage is expected to be non-viable.
Appear on exposed reservoir bed
The species is believed to have its origin in Tropical America (Northern S. America to Central America). Due to its popularity in floriculture, the spider plant now has a wide distribution in many tropical countries in the African, Asian and Australian Continents.
According to Dimuthu, CEB Engineer in charge of the Maussakele Reservoir dam who provided valuable information during our visit there, this mass blooming of the Spider Flower has been observed on previous occasions, the last, about 1-2 years ago when the reservoir went this dry.
He also said, the residents have already coined a local name “Maussa-mal” for the plant. It is obvious this gregarious spider plant population at Maussakele, amounting to tens of thousands, perhaps more, would have sprung from an enormous quantity of seeds lying submerged on the reservoir bottom for a considerably long time, such as 1-2 years.
With the reservoir’s water level this year is going down by about 20-25 metres exposing the bottom and then sunlight and air becoming available on this artificial wetland with its super fertile alluvium, seeds would have been germinating almost simultaneously followed by a fast growth of herbs and a burst of bloom. Dimuthu has not observed this mass blooming phenomenon in other parts of the Maussakele Reservoir or in the Castlereigh Reservoir in close proximity to the former.
It is presumed, a small pioneer Spider Flower population developed from a few seeds arriving on this exposed reservoir bed several years ago from flower beds above this site. It is probable that a stream traversing the Maskeliya township would have conveyed seeds to this site. Due to very favourable conditions with mineral-rich alluvium, the first settlers would have thrived vigourously producing seeds in their maximum capacity.
Few successive generations appearing with every exposure of the reservoir bed would have resulted in an exponentially increasing population of the plant.
However, the above mechanism does not operate regarding the establishment of small populations of other species in the same habitat. Those such as Floss Flower and “Hulan-tala’ are naturally occurring or naturalized species in the surrounding areas and their seeds are dispersed by wind and when they deposit on the exposed reservoir bed they quickly germinate and form small populations, but are unable to compete with the relatively more vigourous Spider Flower.
When the reservoir is full
According to the local residents, with the onset of the rains and when the water level rises above the Spider Flower population, fish devour them (Tilapia fish has been introduced in the reservoir). By this time, the seeds are expected to lie on the reservoir bed and gradually get covered by sediments and wait till the next drought when the ground is exposed, to spring up the next generation.
It is known that the seeds in water, after a short spell of floating, sink to the bottom. Although the Spider Flower seeds can germinate after 4-5 days after their release, experiments have shown that they germinate well even after one year. However, their ability to survive under submerged conditions for a long period of time, such as 1-2 years, is clearly proven by the present observation. Sufficient seeds (in millions) that have raised this massive population would not have come from outside, either blown in by wind or carried by water (streams). Further, large Spider Flower plant populations have not been observed around the Maussakele Reservoir.
Will Spider Flowers bloom again?
If the water level drops to this low within a year or two, it is very likely for this spectacular phenomenon to appear again. If the water level remains high for a longer period and if the seed viability does not extend beyond two years or so, we may not see this again. Anyway, experimental evidence on seed viability, especially, under submerged conditions, will help in predicting the future of this mass blooming at Maussakele.
How nature responds to human impacts
The construction of a reservoir causes an extreme change in the environment. For the total vegetation and for all other man-made structures, the reservoir becomes a watery grave. During droughts when its peripheries are exposed, nature converts these apparently barren and desolate landscapes into amazingly beautiful meadows decorated with colourful flowers – only to disappear during the next rainy season, thus teaching us about the uncertainty of the beauty.
The writer is Senior
Consultant, EML Consultants (Pvt) Ltd.,
former Director, Plant Genetic Resources Centre,
Department of Agriculture, and former Curator of the National Herbarium,
Royal Botanic Gardens, Peradeniya