Aquatic Plants For Pond: Swamps, Oxygenants And Floats

Aquatic Plants For Pond: Swamps, Oxygenants And Floats

The Flora Of Water Gardens

From a biological point of view, the whole of all aquatic plants can be reduced to three groups:

  • that of wetland plants;
  • marshland;
  • that of aquatic plants, both fixed to the bottom and floating.

They differ in their physiology and it is necessary to have some elementary knowledge for their use. Due to the considerable choice of all these groups of plants, it will be necessary to select some plant species. If you have a small garden with a small tank, it is useful to keep in mind that real aquatic plants, living under the surface of the water, are less visible than marsh plants and for wetlands whose leaves and flowers, often considerable, exceed the level of the water surface. Since it is not possible to grow them all, the latter will be preferred over the former. On the contrary, if you have a large lake where all the heights of water necessary for the cultivation of plants are represented, it is clear that the choice of plants will cover all the groups mentioned above.

Plants For Wetlands

Wet soil plants occupy a particular area taking advantage of the presence of a cool but ventilated soil and a humid atmosphere thanks to the presence of water, which is essential for their survival. These plants do not necessarily grow near a pond. Occasionally they can be found in undergrowth, near springs, along drainage channels or in valley floors with marshy soil. They can withstand short periods of drought but degenerate if they are deprived of water for a long time. Their importance in furnishing a garden is fundamental for two reasons: they are often more colorful than purely aquatic plants and, moreover, their generous vegetation allows them to enlarge the space around the pond giving the impression that it looks bigger than it actually is.

Marsh Plants

“The feet in the water and the head in the dry”: the marsh plants occupy that area of transition between the domain of water in the strict sense and the rest of the garden. The upper part of the plant, foliage and flowers, develops above the water level, while the collar and root system are in the water. The epidermis of the air organs is often covered by an impermeable cuticle with stomata. The cuticle prevents the plant from drying up, whilst the stomata ensure the functions of chlorophyll assimilation, transpiration and respiration, water vapour elimination and gaseous exchanges. The parenchyma (tissue that forms the active part of a plant organ) of marsh plants is somewhat similar to that of certain aquatic plants in that it contains aeriferous gaps. The conductive tissues are highly developed; the supporting tissues of the cellulosic or lignified walls are always present and ensure the rigidity of the air organs. The root system is highly developed, serves for maintenance and allows the absorption of nutrients dissolved in water or present in the substrate. Thanks to this organization, these plants are not afraid of drying out.

Aquatic Plants

Their epidermis is usually green, without cuticle or stomata, but however permeable to gases and salts dissolved in the water as well as to oxygenants. In those having floating leaves, such as the water lilies, the upper epidermis in contact with the atmosphere has cuticle and stomata. The aeriferous gaps are more developed and allow the support of the leaves and stems by floating. Generally these plants are attached to the substrate with short roots, except for plants that have tubers or rhizomes such as water lilies. The conductive tissues are very small because it is the epidermis that absorbs the nutrients dissolved in the water. Their transpiration is almost zero and desiccation cannot take place; gaseous exchanges take place by diffusion through the epidermis of the stem and leaves.

Vegetable Physiology

All these plants, whether for wet, marshy or aquatic soils, are linked to four limiting factors (law of the minimum), imperatively conditioning their life, growth and reproduction. These are light, carbon dioxide, temperature and nutrients. The first three factors are intimately linked and participate in the primordial function that is chlorophyll assimilation or photosynthesis. To this is added the process of nutrition of the plant from organic and mineral substances.

Waterlily: Water Queen

Well anchored at the bottom of the lakes, they let leaves and flowers float on the water. Since ancient times, water lilies have aroused admiration and veneration among the peoples of Asia. The Egyptians have left us through the frescoes of the temples and tombs a faithful representation of the Nymphaea lotus with its white flower and the Nymphaea caerulea the famous blue lotus of Egypt, two tropical species that populated the ponds of the Nile valley 5000 years ago. Another species of blue water lily, the Nymphaea stellata, was, in India and China, the sacred flower of the Buddhists in the same way as the Nelumbo nucifera the sacred pink lotus of Asia. In Europe, the Nymphaea alba and the white-blossomed white Nymphaea were the basis of many popular myths and beliefs. They symbolized beauty and elegance for the ancient Greeks, who saw in them the representation of the Nymphs and water spirits. For the people of Central Europe they had the power to ward off evil spirits. In the last century they inspired great painters like Monet who painted his famous paintings in his garden in Giverny. Today these beautiful aquatic plants are cultivated as ornamental plants. The easiest to cultivate are the rustic water lilies. They disappear completely during the bad season and are able to withstand the harshest winter, provided their rhizome is kept above freezing level. All water lilies love sunny locations and warm water. The daily hours of sunshine should be at least six to encourage good flowering. Few varieties can tolerate semi-shaded positions (Hermine, Comanche). These plants start to vegetate at the end of winter when the water starts to warm up. First the leaves develop and only later, in mid spring, do the flowers come out. The greatest growth occurs in the warm months of summer. In autumn, as the temperature drops, growth slows down until it stops completely at the end of October. Depending on the species, the planting depth can vary from 15 to 200 centimeters. The rhizome is still tenaciously at the bottom and produces long petioles that end at their end with a solitary leaf. The leaves submerged during growth are rolled up like a horn. The flowers, which can reach 20 centimeters in diameter as in the Attraction, open at ten in the morning and close at five in the afternoon throughout the flowering season from April to September. After fertilization, the petals and sepals close to form a globular and leathery fruit which can contain up to 1500 seeds. The fruits come off after ripening to overwinter at the bottom of the pond. In spring the seeds rise to the surface to be dispersed by the wind and water birds. Each water lily can cover about one square meter. The limitation of the leaves is a small expedient that will allow us to obtain a more abundant flowering.

At What Depth Should They Be Planted?

It is important to respect the typical indications of each species. A depth of 60-80 centimeters, in any case, meets the needs of most water lilies. Shallow water heats up quickly and promotes a generous and early flowering. In the small ponds we choose species of reduced development that can grow up to 15 centimeters. In large ponds we choose species of large development that can withstand depths of 200 centimeters; keep in mind that at this depth the flowering decreases.

What Kind Of Soil Do We Use?

Water lilies love common garden soil, better if clayey and a bit slimy, rich in organic substances. We avoid adding manure, as many people suggest, because by osmosis such a high quantity of nitrogenous substances would be released into the water that it would cause uncontrolled algae growth. If the soil used is excessively poor, we use slow release balanced fertilizer that will be placed on the bottom of the pot.

How Do We Plant Water Lilies?

The rhizome should be buried up to the leaf collar, slightly inclined, so that the terminal part touches the wall of the pot while the growth apex can develop towards the centre of the pot. In large natural ponds, water lilies should be planted directly into the silt at the bottom. If the water level cannot be lowered, we tie a stone to the rhizome and throw it where we want the water lilies to appear. In an artificial pond we can grow them in the same way after having prepared the bottom with twenty centimeters of soil and five centimeters of sand. Otherwise we grow them in plastic containers at least thirty centimeters in diameter. This method allows us to better control the growth of the plants and intervene for division at the right time.

Oxygenating Plants

These plants, which live completely submerged, are not spectacular and not even beautiful, but surely the most useful ones. Present in a certain quantity, they ensure clear water. Oxygenating plants play a fundamental role in the life of a pond. They release large quantities of oxygen during the day, which is vital for all living organisms in the pond. Their number must be proportionate to the amount of water in the pond. If they were reduced in quantity the oxygen would be insufficient, algae growth would be encouraged and the water would turn green. If the number of algae is too high, the growth of other plants could be suffocated. It will be useful to plant them in pots to avoid excessive proliferation and invasion, which would be difficult to contain if they were planted in the ground. In addition to oxygenating these plants offer an excellent shelter and food to all newborn fry often easy prey for adult fish.

Elodea Canadensis (oxygenating)

This perennial, rustic plant takes root easily at the bottom. It forms long stems that come close to the surface. It grows rapidly in early spring and stabilizes as the season progresses. To reduce its volume, simply pull out some tufts with the same hands. Very effective oxygenating plant, it is very easy to grow. It should be planted from 30 to 150 cm of depth, better in pot to control the development.

Ceratophyllum Demersum (oxygenating)

Excellent oxygenating plant. Its stems produce numerous small, finely divided leaves; this prevents the bottom of the pond from becoming obscured despite very vigorous vegetation. It can be planted in pots or left to float freely.

Hippuris Vulgaris (Oxygenating)

Planted deep, it remains totally submerged. In shallow water, the stems rise up to 40 cm above the surface to form small fir trees. It has a good oxygenating power.

Floating Plants

They seem to live on fresh water. Some of them are “pests”, due to their excessive development, others are jewels, due to their strangeness, but all of them are extremely useful in cleaning the water of a small lake. They are plants floating freely on the surface of the water. The leaves are structured in such a way as to contain micro-bubbles of air which allow the plant to float. They produce masses of roots that grow under water and absorb the mineral salts dissolved in it. For this reason they are very useful as biological purifiers, reducing organic pollution and avoiding water numbness. Some are tropical and cannot withstand the winter rigours of our latitudes. If they are to be stored for the following year, in October they must be collected in a heated greenhouse or at home. It is sufficient to use a small plastic container; you cover the bottom with a centimeter of silt recovered from the pond by covering it with sand, fill it with water from the pond and place it in front of a window in full light. Every fortnight a balanced liquid fertilizer is used.

Rustic Floating Plants

Lemna minor or water lentil. It is very intrusive, covering the entire body of water and removing light from the oxygenating plants. It is easily eaten by fish. Trapa natans or water chestnut. Very beautiful for its rhomboidal emerald green leaves, it begins to produce at the end of summer seeds as big as a chestnut with hard, sharp thorns. When the plant dies before winter the “chestnuts” fall to the bottom. In spring they germinate forming new seedlings on a long stem that grows to the surface.

Stratiotes aloides or water pineapple. In winter it rests on the bottom to overwinter. In spring it resurfaces again. It forms colonies by vegetative multiplication. Produces beautiful white flowers from May to July.

Tropical Floating Plants

Eichornia crassipes or water hyacinth. It is a very beautiful plant that produces a magnificent blue mauve flower from July to September. It is composed of a rosette of leaves whose petiole is enlarged into a ball giving it a very curious appearance. For its intrusiveness, only a few seedlings are needed in a pond.

Pistia Stratiotes Or Water Lettuce

The thick, light green leaves arranged in a rosette vaguely resemble a lettuce strain. Its highly developed roots are used by fry as a refuge. It is very intrusive.

Marsh Plants

Their leaves and flowers develop free in the air, but the roots grow in water and do not tolerate dry soil. Marsh plants populate the area that connects the earth to the water. In a natural pond, they can easily be planted directly in the silt at the bottom near the shore at the desired depth. In an artificial pond these plants should be placed along the edges. A brick wall or stones placed on the bottom can be useful to contain the earth and prevent it from landslide downwards. Most of these plants have great vigor and in small to medium ponds should be planted in pots to control their growth, cutting the roots regularly and dividing them every two or three years. If different depth levels were not foreseen when the pond was built, it is often necessary to use bricks to lift the pots up to below the surface of the water. When choosing the number, the rule is to avoid an excessive mixing of different species. It is better to have a small number of varieties with numerous specimens for each group.

Houttuynia Cordata

Excellent upholstery. Ideal for masking the rocks used to cover the edges of the sheet. Leaves and flowers smell of unripe mandarin. Grows in any position.

Butomus Umbellatus

It stands out for its inflorescences that culminate with about fifty pink flowers grouped as an umbrella. It quickly forms colonies if the soil is very rich in nutrients. Loves sunny locations.

Scirpus Tabernaemontani

It forms dense colonies of tubular stems up to one and a half meters high that swing in the wind. The ‘Zebrinus’ variety is horizontally variegated with white and green stripes, the ‘Albescens’ variety is vertically variegated with yellow and green stripes. They grow well even in half shade.

Sagittraria Sagittifolia

is a plant able to adapt to live in all positions by changing the shape of the leaves according to the planting depth. If planted on the bottom it produces ribbon-shaped leaves. At water level they become lanceolate. When the plant is on the edge it produces clearly sagittate leaves.

Lysimachia Punctata

Easy to grow, Lysimachia grows quickly, whatever the soil or exposure. The flowers, shaped like yellow bells, are grouped in spikes. The plant reaches a height of 60 to 120 cm. It should be planted at a depth of 10 cm. at a ratio of six plants per square meter.

Glyceria Maxima “Variegata”

This beautiful grass is ideal for populating the edge of the pools. With its very long, variegated leaves, which move with every breeze, it animates the edge of the pond. Its root system is beneficial for the solidity of the banks. It can be planted up to 50 cm. deep, at the rate of 10 plants per square meter. In small ponds it is better to plant it in a basket.

Equisetum Hiemale

Horsetails are much feared in gardens, but find their ideal place in ponds. Their very attractive stems reach a height of 120 centimeters and remain green all winter long while around them, most water plants disappear.

Water Irises

They must never miss the edge of a pond. Their flowers are splendid, even if not very long lasting, and their linear and vertical leaves contrast with the horizontal plane of the water. They must be divided in two groups: aquatic irises can live in the water all the year round, like the genera ‘Laevigata’, ‘Pseudacorus’, ‘Versicolor’, ‘Setosa’ and ‘Luisiana’. Marshy irises do not like to have their feet in the water even during winter rest like the genera ‘Ensata’ and ‘Sibirica’.

Orontium Aquaticum

The flowers of the orontium resemble large matches or candles lit on water with the yellow end and long stem. A very unusual flowering. To appreciate it, starting in March, it is best to plant it at the edge of the pool. The plant forms a very dense tuft of bluish green lanceolate leaves. It reaches a height of 45 cm. and you need six per square meter.

Juncus Effusus

The reeds are perennial and rustic plants, they have cylindrical stems and leaves. Their brown fruits are as interesting as in Juncus ensifolius. Some varieties can reach 1.5 m in height. Juncus effususus ‘Spiralis’ is very decorative with its spiral leaves. You have to plant them very close together to get dense tufts that are more pleasing to the eye.

Marshy primroses

Of all the perennial wetland primroses, those grouped under the name ‘Candelabrum primroses’ are certainly the most spectacular. They produce flower stems from 40 to 90 cm high, on which flowers of different colors bloom at regular intervals. Among the most recommended: Primula japonica (pink, red or white), Primula bulleyana (yellow and orange), Primula beesiana (magenta pink), Primula florindae (yellow). They should be planted flush with water.

Mentha Cervina

The mind is a perennial, rustic and melliferous plant. There are more than a thousand varieties of which some thrive in shallow water. It is best to grow them in pots to control the expansion of their very vigorous roots.

Thalia Dealbata

This beautiful rustic plant of subtropical origin possesses solitary glaucous green oval leaves, with a horizontal position on long stems at the end of which an ear of purple flowers develops. Because of its elegant profile it is a precious plant for creating an exotic scenery. It cannot stand frost, but it is sufficient to place the strain below the freezing line.

Pontederia Cordata

It is a plant widely used in the furnishing of a pond. Its lanceolate leaves are very decorative and its lilac blue flowers are very appreciated and bloom in summer, when there are no other flowering plants. It loves sunny locations. It reaches a height of 90 cm. and to fully appreciate its posture it is necessary to plant it in groups freely or in large pots.

The Lotus Flower: Symbol Of Purity

Known since ancient times, lotuses are among the oldest cultivated plants. The symbolic content of this plant is extremely powerful in Buddhist religion. In temples there are often pools full of lotuses. Buddha is represented sitting on a lotus flower that represents the purity of the muddy waters. Nelumbi, in Asian countries, are also cultivated for food purposes. Of it all is consumed. The seeds are roasted, the rhizomes replace our dear potatoes and the young leaves, when they are still wrapped around themselves, are used to make excellent soups. It seems that nothing is worth a good lotus leaf soup to spend a peaceful night. The Vietnamese often give their slightly agitated children a lotus seed before going to bed with surprising effect. The Chinese cultivate a lotus variety with thicker rhizomes and close internodes for purely nutritional purposes. The lotuses are native to the Indies, the banks of the Volga, North Australia and North America. Instead, their presence on the edges of the Nile is due to human intervention around 500 BC. The lotus of the Nile exists, but it is not a nelumbo, but a blue water lily, the Nymphaea coerulea endemic to the river. It is a rare tropical botanical waterlily, often found in the frescoes of Egyptian temples. Although very different from the morphological and vegetative point of view, the lotuses belong to the Nymphaeaceae family, although some authors still include them in the Nelumbonaceae family. The vegetation of these plants is extraordinary. Only the first leaves, like the water lilies, float on the water, while all the others stand out towards the sky. The largest varieties reach a height of 180 cm. The flat or slightly funnel-shaped, dark green, bluish green or bronze green leaves are supported by slightly thorny peduncles. The flowers emerge from the foliage to bloom in full sun. The banana-shaped rhizomes, white in color, are covered internally by canals. When they develop, they produce a very long stolon which, at the level of the nodes, gives rise to secondary rhizomes. There are only two botanical species of lotus: Nelumbo lutea, native to the United States, and Nelumbo nucifera, native to the Indies. Latour Marliac was the first hybridizer to obtain a lotus hybrid: the Nelumbo ‘Flavescens’. Dozens of cultivars have been obtained in America from numerous hybridizers. Almost 300 cultivars have been obtained by the Chinese in the last twenty years. Most of them are small in size.

Lotuses In The Water Garden

The lotuses are of great decorative interest. Their presence gives an exotic note to the whole body of water. At the edges or in the middle of the water, they grow with the luxuriance typical of tropical plants but without having their fragility. Only the Victoria director can stand up to them. When you are lucky enough to have the two species living together in the same tank, you have the impression of being in the land of a thousand and one nights.

Cultivation And Maintenance

The cultivation of lotuses does not present particular difficulties if these simple advice is followed. The lotuses want a sunny area from morning to evening so that the water can reach a temperature of 25 degrees as the season progresses, a primary condition for stimulating flowering. Sustained fertilization is a prerequisite for lush vegetation. It should be borne in mind that lotuses are capable of producing stolons more than six meters long in a year. The rhizomes of the previous year are dying to feed the vegetation and future flowering and at the same time they must find enough resources to remake the rhizomes of the future year. These plants must be grown either in closed tubs or in sectors of your pond isolated from the rest of the pond. In any case, if you do not want your water garden to become a virgin forest, you must imperatively bar the advancement of the roots. The ideal space to appreciate this plant should be 2 square meters of surface area by 60 cm deep, of which 40 cm filled with substrate and 20 cm of water. In order to insert the fertilizer without difficulty in spring, it is necessary to wait for the first floating leaves to appear, then wrap the fertilizer in a sheet of newsprint, make holes with the help of a stick and insert these candies in the holes closing them immediately afterwards. The method is simple and effective when the water level cannot be lowered and the newspaper quickly degrades. For a first plantation, the fertilizer will be hidden under the whole surface then a furrow of the shape and size of the rhizome with a depth equal to three times the thickness of the rhizome will be traced, a dose of fertilizer (50g) will be laid then covered slightly with substrate. The lotus will be deposited in this excavation, the lotus will be buried taking care to leave the apexes of growth free from the soil; above all it is not necessary to crush the substrate because the plant is very fragile like glass, finally a flat stone will be placed sideways on the rhizome to ballast it and it will be filled with water without causing turbulence.

Tropical Water Lilies And Lotus Flower

The tropical water lilies are even more spectacular than the rustic ones because their flowers are large, they are emerging, they are very perfumed but above all they have a color that does not exist among the rustic ones: blue. Their countries of origin are Australia, the Far East, Africa, South America. In these countries they populate stagnant waters and slow streams. The number of tropical water lily species is considerably higher than that of rustic water lilies. The flowers of all tropical water lilies rise about twenty centimeters above the water surface and are produced in large quantities. The leaves are larger and more decorative because they are often colored, purple veined and serrated at the edges. In northern Europe they are grown exclusively in heated greenhouses or winter gardens. Here they can be grown outdoors in the summer and protected in the winter months. The sacrifices that must be made in conserving these water lilies in winter are largely compensated by two unique characteristics: only among tropical water lilies are there varieties with blue flowers and some species bloom at night.

Care And Maintenance

Most of these water lilies are bulbous plants and are relatively easy to grow provided, however, that they meet certain requirements that are indispensable for their vegetation.

  1. The substrate must be rich in organic matter and composed of clayey soil mixed with sand.
  2. The bulb must be planted at a depth of no more than thirty centimeters.
  3. The water temperature must be at least twenty-five degrees. In the north of Italy this temperature is easily reached in June.
  4. Tropical water lilies need a lot of light to develop; they must be planted absolutely in the sun.
  5. It is necessary to limit the number of leaves to stimulate the plant to produce more flowers.
  6. The bulbs of these plants must be withdrawn before the autumn frosts. They can be stored in damp sand and stored in a room with an average temperature of ten degrees. If unfortunately the bulb is hit by frost, the water lily is lost.
  7. During the growing season they must be fertilised once a month with a balanced, slow-release fertiliser.
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