It is hard to miss the rocky hills abruptly rising from the relatively flat landscape when travelling to or from Bangalore. Such a hill in ecological terms is called ‘Inselberg’ which is German for ‘island mountain’. In the tropics and subtropics, they form prominent landscape elements rising abruptly from the surrounding plains, with their age often exceeding 20 million years. They are certainly islands today and are home to the last remaining pockets of wildernesses. These hills are wonderful places to explore and there is a spark of joy that comes from walking on the granite surfaces of these hills. There is a lot to take in – patterns and formations of rocks, crevices, cracks, depressions, lichens and the thin mats of soil with the most interesting assemblages of miniature plants. For almost half the year during the hot dry season, these hills look dry and desolate, but there are invisible lifeforms in all the nooks and corners.

A rock pool claimed by plants like Rotala fimbriata, Ludwigia and some sedges.

The monsoon season is a time when everything is rejuvenated. This is most apparent in seasonally dry forests, such as the hills around Bangalore, which spring to life with an abundance of green in a way that the whole place is transformed completely. Grasses and small herbaceous plants grow quickly and complete their life cycle during the few months when water availability is not a problem. It is also during this time that the rock pools come to life. The relatively old (hundreds of years) rock pools form a unique habitat in these granite hills. They occur as seasonally water-filled depressions with a thin layer of soil mainly inhabited by ephemerals (short lived herbaceous plant species) and cryptogams (algae, lichen, mosses, ferns).

A rock pool with Rotala fimbriata, a plant that completely specialises in growing in rock pools.

It is actually hard to find Rotala fimbriata growing anywhere else! A very pretty plant with linear opposite leaves and tiny pink lacy flowers, it is easily spotted around Bannerghatta, Savandurga, Ramadevarabetta, etc.

A rock pool filled with thousands of tiny individual plants called duckweed, Lemna sp. The bushy plant is a Ludwigia sp. which also prefers rock pools.

The periphery of rock pools is very interesting too, where one can see tiny plants like the Murdannia semiteres, which has 3-petalled blue flowers. The entire plant is a just a few centimetres tall.

These white buttons are characteristic flowers of a group of plants called pipeworts – Eriocaulon. The scientific name is derived from Ancient Greek εριον, erion, meaning ‘wool’, and καυλός, caulos, meaning ‘stalk’. This plant only grows in wet marshy areas such as paddy fields, inundated grasslands, and rock pools with higher organic matter content. These tiny flowers are wind-pollinated.

Marsilea quadrifolia is an aquatic fern with clover-like leaves which can occasionally be seen. Hard to imagine they are ferns, right? Their rhizomes and their fruiting bodies which bear the spores can survive dry periods for very long periods of time and sprout when water is available.

Grasses can grow in these pools too, like some species of Echinochloa. Other plants in this pool are Aeschynomene sp. and growing submerged inside the water is Dopatrium junceum. Many species that grow in these shallow seasonal pools develop special adaptations like spongy roots that help them float, breathe etc.

Lindernia hyssopioides waits for the water to dry up and then produces these dazzling blue flowers. There is a succession of plants in these pools. As the pools are constantly in flux, there is a plant for each stage of water availability – submerged and floating plants when the pools are full, sedges and grasses when the depth is reducing, Lindernia, Cyanotis, Murdannia etc. when the water is gone but the surface of the soil is still moist and so on. What is amazing is that all the seeds/tubers are present in the rock depressions, and they know exactly when it is their turn to grow.

A drying pool with a neat little assemblage of at least 3 species of sedges, Cyanotis fasciculata (pink flowers) and a tuft of Rotala fimbriata.

Over time these pools may fill up with organic and inorganic material and become favourable enough for other plants to grow in them. Here is a big tuft of Heteropogon contortus grass in what seems to be a depression in the rock. It may look nice and benign now but come summer and the needle sharp seeds of this grass will pierce through the clothing, socks, even skin of anyone who walks through them.

When the pool is bigger and deeper like a pond, larger aquatic plants also come up in them, such as water lilies and fascinating blooms of Aponogeton, seen in this photograph. They are tuberous species which can resprout each year. The tubers are also edible and relished by locals.

Aponogeton occupying an entire pond near Kanakapura.

Some interesting animals can be seen in these habitats as well. Skittering Frogs are easily spotted in these pools, floating on the surface. Dragonflies and damselflies use these pools as nurseries for their larval young which are aquatic. These pools are interesting geomorphological features and play an important role in the ecosystem by holding water, providing food and shelter to various species of plants and animals.