Ajuntament de Barcelona

The aquatic plants

Mossèn Cinto Verdaguer Garden

    Yellow flag

    Most of the plants that live rooted to the ground are unable to resist the conditions of a flooded environment. On the other hand, the aquatic plants are adapted to live in the water or in very wet environments.

    There is a big variety of aquatic superior plants, called hydrophytes, that live in fresh water and in salt water. A big proportion of aquatic plants live in lakes, ponds, pools and marshes (lotus, saw-sedge) or in slow course rivers (Callitriche obtusangula), whereas other plants live in running waters and in salt water, as the estuaries, the lagoons and the sea (Posidonia). The aquatic plants can be classified according their immersion degree: some of them live completely submerged and are rooted to the bottom (Potamogetum crispus, Canadian waterweed); some others float freely and move depending on the water currents or the wind, either over the surface (common duckweed) or under the surface (bladderworts); and other submerged plants are anchored to the bottom by roots and part of their stems, leaves and flowers emerge from the water, such as most of the plants that you can see on ponds at Mossèn Cinto Verdaguer Garden (water lily, calla and lotus).

    The aquatic plants play an important role in the aquatic ecosystems, because they offer directly or indirectly food, protection and a big variety of habitats to a high number of organisms and they facilitate to maintain the water clean and oxygenate. They are very used in ponds and pools at many green spaces and landscaping interventions because of those characteristics and of the beauty of the flowers of some of those plants. 

    Characteristics: 

    To adapt to the aquatic environment, the plant presents some special characteristics. The submerged ones are permeable and absorb nutrients and swap the gases directly from the water. The ones where part of their body is out of the water, they oppose little resistance to the water waste, as opposed to the plants that are adapted to dry environments, as the xerophyte ones; because of that, the leaves and steam’s waterproof coating is minimal and the plant has opened and surface stomas.

    The main limitation of the aquatic plants, especially those living anchored to the bottom, is to provide themselves with the necessary oxygen for the root respiration. This is why many of them have the body (stems and leaves) fulfilled with wide spaces that are real channels where the air circulates from the atmosphere to the roots; at the same time, these channels maintain the plant floating or upright on the water, such as in the case of the water lilies and of the lotus flower. The trees, such as the bald cypress, have special breathing roots, named pneumatophores, which emerge from the water to collect the oxygen. Other trees, like the black poplars, have pores (lenticels) on the bottom of the trunk to collect the air. The floating aquatic ones, such as the Lemna, have little air tents under the leaves that serve of float.

    Another important aspect of the plants’ adaptation to flooded and swampy environments are the biochemical processes that avoid accumulating the toxic products typical of the conditions of lacking in oxygen or anaerobic environments.

    The aquatic plants are very used in landscaping and in gardening and to regenerate polluted water because of their beauty (they have spectacular flowers), because they take in very different animals and because they are able to enrich the aquatic environment with oxygen and, at the same time, to reduce the nutrients and pollutants levels. For this reason, the polluted water is channelled through artificial wet areas in order to remove any mineral and organic substances and heavy-metals. Currently, one application of this is the creation of ecological swimming pools with aquatic plants to depurate the water.

    The most used in gardening are the calla, with big white flowers, the yellow iris, with yellow flowers, the pickerelweed, with blue flowers, and the lotus flower, with whitish or pink flowers. Over all of them, it stands out the water lily (Nymphaea), with bright leaves and varied in colour (depending on the variety) flowers. All the water lilies cultivated in Catalonia are species coming from the hybridisation of the European white waterlily, the indigenous Nymphaea, and several species of tropical Nympheae.

    The planting at ponds or wet areas are made at different depths, using the levels depending on the necessities of every aquatic plant or else on flowerpots that are put into the water.

    History and curiosities: 

    The aquatic plants are an important source of human food: rice (which originally was not an aquatic plant), wild rice, darnel, watercress, wasabi... These kinds of plants play a cardinal role on the diet of wide world areas, such as South-Eastern Asia. As well as serve as food, many aquatic plants have been used since ancient times as building materials, to make roofs, furniture and ships, as raw materials for industrial and textile processes and as a farming fertilizer.

    They bring large profits, because they help maintaining the water clean and recovering the polluted one, although they can also cause damages if they develop too much, for instance blocking navigation canals, interfering in the fish farms, returning the non-drinkable water, etc. 

    For further information: 
    Yellow pond-lily
    European white waterlily
    European white waterlily
    European white waterlily
    European white waterlily
    European white waterlily
    Pickerel weed
    Pickerel weed
    Arum lily
    Arum lily
    Yellow pond-lily European white waterlily European white waterlily European white waterlily European white waterlily European white waterlily Pickerel weed Pickerel weed Arum lily Arum lily