AQUATIC

What Is An Aquatic Plant?

An aquatic plant is a plant that lives in (and sometimes on the margins of) water. These are one of the types of plant you will need to consider if you plan to create a pond in your garden.

Choosing aquatic plants should always begin with a consideration of where exactly you live, and what the conditions are like there. With aquatic plants as with other plants elsewhere in the garden, it is important to choose the right plants for the right places. If you don’t really know where to begin, the staff in an aquatic plant nursery, or in your local garden centre should be able to help.

Wherever you live, however, there four different categories that you will have to take into account when you choose plants for your pond. You have to remember that you want to create a balanced natural ecosystem, and that means that you need:

  • Aquatic plants that root beneath the water.
  • Marginal species which live in boggy ground and around pond edges.
  • Submerged plants (which oxygenate the water) and
  • Plants which float on the pond surface.

As elsewhere in your garden, diversity is key when choosing pond plants. Aim to incorporate as many different aquatic and marginal plants as possible.

Rooted aquatic plants are typically purchased as container-grown or bare-root specimens. They are planted in special containers/ aquatic baskets that are placed in a pond or other water to allow the leaves to float on the surface. Newly purchased plants of this type may need to be placed on bricks in the water to raise them to the right height, then lowered in stages as they grow.

Marginal plants thrive either on the damp edges of a pond, or in very shallow water at the edges of it. They can also thrive in a bog garden – liking damp and waterlogged conditions.

Submerged oxygenating plants are another important type of plant to include in your pond. You will usually purchase bunches of these plants, that can be placed into your pond and secured in place. As a general rule of thumb, you should include 4 or 5 bunches, each containing 3-4 stems, of these plants for each square metre of pond surface area.

Floating plants are a fourth type of aquatic plant to introduce to your pond. These, as the name implies, float on the surface of the water. Some floating plants are aquatic weeds that you do not want. But some floating aquatic plants can be beneficial.

Popular Aquatic Plants Grown In The UK

There are many popular aquatic plants to choose from for your garden pond. But here are some of the popular options that you might like to consider:

When choosing aquatic plants, it is important to avoid any that can become invasive, and also those which can overwhelm a smaller garden pond. Be sure to choose options from each of the four types of aquatic plants to create a healthy and biodiverse system.

What Conditions Do They Prefer?

pink water lilies on a pond

The conditions which an aquatic plant will prefer will of course depend on which type of aquatic plant they are. All will thrive in or around a pond – though some will not be suitable for a pond of the size that you have created. It is important to consider where the aquatic plants are to be used before you start trying to decide which ones are right for you.

When it comes to rooted aquatic plants and marginals, the key thing to consider is how deep your pond or container needs to be. Some will thrive in deeper water (30cm or more), some in a depth of 15-30cm, some in 5-15cm of water, and some in very shallow water or waterlogged and muddy soil. A number of waterlilies, popular aquatic plants in the Nymphaea genus, will need water that is 30-45cm, or even 45-75cm deep.

Choosing the right spot for your garden pond or aquatic feature in your garden is very important. Aquatic plants will not necessarily thrive if your pond is placed in an unsuitable spot and does not provide the right environmental conditions.

Be sure to think about sunlight and shade, for example. If you are creating a wildlife pond, you need to take into account not only the needs of the aquatic plant life, but also of the other creatures that will use it and live in it. Much of the wildlife using your pond will prefer it to be in direct sunlight. But to keep the algal growth down, a partly shaded spot may be better.

The pond should have dense foliage cover up to the edge along at least one side. If the area around the pond is too open, this will make it more difficult for visiting wildlife. And when wildlife does not use the pond as it should, the system as a whole will not be as resilient. Remember, plants need animals and animals need plants. And increasing the range of beneficial interactions will ensure that your organic garden thrives.

The shape of your pond is also important, both for the plants and the wildlife. It is best to keep the shape natural and to make sure there are varied depths. This will provide conditions for as wide a range of aquatic plants as possible.

Ideally, your pond should have a deeper section in the middle (if you can, a depth of at least 60cm at the centre is best), shallower sides, and one end that slopes gently to a sort of beach area. A gently sloping side not only allows for the inclusion of marginal plants, but also provides an escape route for any wildlife that might accidentally fall in. Make sure the edges of the pond are level and water will not escape and a lip be left at the other side.

Make sure you choose a durable lining for your pond. Or, for a more natural and eco-friendly option, consider lining your pond with clay.

If you are using a small container to make a tiny pond for a small garden, make sure you leave a branch or something else sticking out from one side, so any creatures that fall in can escape.

If you can, it is best to fill your pond with rainwater, or water from a natural spring or other water source. Treated tap water will not be as good for aquatic plants or wildlife. If you can, add a bucket of water from an existing pond to give the ecosystem a head start.

What Conditions Should You Avoid?

One thing that can cause environmental issues for aquatic plants is temperature. It is a good idea to make sure that the water will not freeze solid in winter, or overheat in summer.

Wind is also something to consider. Place your pond or water feature in a spot that is as sheltered as possible. This makes it easier for insects and other creatures that like to sun themselves around the pond. Consider prevailing wind direction because if leaves and debris accumulate in the pond, the system, and the plants and other life within it can suffer.

Make sure you have oxygenating plants so that the pond remains in balance. And make sure that nothing disrupts the pH or nutrient levels in the water.

Frequently Asked Questions

What Are The Best Aquatic Plants For Small Containers?

If you are planning on growing aquatic plants and making a pond in a small container, it is important to choose plants that will not grow too large, and which will not take over. Some good options to consider for a small container or small pond include:

  • Nymphaea leibergii (Dwarf water lily)
  • Nymphaea ‘Pygmaea Helvola’
  • Nymphaea tetragona
  • Nymphaea odorata var minor
  • Hottonia palustris
  • Myriophyllum spicatum
  • Ranunculus flammula
  • Orontium aquaticum
  • Zantedeschia aethiopica
  • Myosotis scorpioides

What Are The Easiest (Low Maintenance) Aquatics To Grow In The UK?

Many aquatic plants are excellent choices for a low maintenance wildlife pond or water feature. I would recommend pond aquatics that are on the list above, of plants suitable for a small pond. Many of these won’t take over too much, and require very little ongoing care.

Which Varieties Are Non-Flowering?

Not all of the plants that you will choose for your pond will have conspicuous flowers. But there are also non-flowering aquatic plants. These are things that you do not want that may show up in your pond. Simple, non-flowering aquatic plants are known as algae.

Algae can pose a problem in an aquatic ecosystem. When they are present, they can upset the natural balance, creating unsightly discolouration, mats of material, or slime-like substances around pond edges. Botanical names for these algae include single-celled algae Chlamydomonas, Chlorella and Euglena, and filamentous algae, Cladophora (e.g. blanketweed).  Though there are hundreds of different algae that can cause problems in ponds.

The main causes of algae in a garden pond are:

  • A site that is too sunny.
  • New ponds that have not yet found their balance.
  • Ponds that were filled with tap water (chlorine content may affect the pond’s natural balance).
  • Fertiliser run-off causing an imbalance in the pond.
  • Excess leaves/ organic debris in the pond that have caused nutrient levels in the water to rise.

Algae can cause deoxygenation of the water, which of course has a detrimental effect on other pond life.

Begin to try to solve an algal problem by eliminating the causes mentioned above, and by making sure that at least 1/3 of the pond surface has aquatic plant cover, and there are plenty of oxygenating plants.

Manually removing algae when you see it can help. But it is best to create an ecosystem that does not get out of balance in the first place.

If the algal build-up has been caused by excess nutrients, you can add a bag of barley straw and lavender (50g per sq m of surface area) to your pond. The container of barley straw is usually added in the spring and then removed, when it has blackened, around 6 months later. Some commercially available products combine barley straw with a beneficial blend of micro-organisms which also aid in solving the problem.

But avoiding or eliminating the root causes of the problem is the only sure-fire way to prevent algae from building up again.

How Do Aquatic Plants Respire?

Just like other higher plants, higher aquatic plants take in carbon dioxide and expel oxygen during photosynthesis. But they also respire and, at night, expel carbon dioxide take in some oxygen instead.

Aquatic plants that are fully submerged have specialist structures on their leaf surfaces that allow for gas exchanges. These include stoma, for example, which is a type of pore. In some plants, these stoma are controlled. They can open or close according to the environmental conditions. Many aquatic plants remain buoyant due to stores of oxygen kept in special vacuoles.

Oxygenating plants in your garden pond release oxygen as a byproduct of photosynthesis, and this oxygen dissolves into the water. By measuring the oxygen in a body of water, scientists can work out whether different aquatic plants are photosynthesising or respiring in different conditions.

How Do They Survive In Water?

Just as land-based plants absorb CO2 from the air, aquatic plants are able to absorb it from the water around them. They can take in this CO2 and through the process of photosynthesis, turn it into glucose. Aquatic plants use photosynthesis and cellular respiration processes to control gas exchange to live.

Plants growing in soil, or in a growing medium in your garden, get their nutrients from the soil. They also take up water from the soil through their roots. Aquatic plants take nutrients and water from the water around them.

Not all aquatic pond plants live entirely submerged in water. Many root below the water but have their leaves above it, and there are also marginal plants, which are typical photosynthesising plants which use sunlight, air, water and nutrients from the air and water or air and boggy soil.

Where Can You Get Aquatic Plants?

Many garden centres in your area will sell aquatic plants. There may also be a specialist aquatic plant nursery near you. Of course, there are also a number of places where you can purchase aquatic plants online.

Can Semi Aquatic Plants Be Submerged?

Semi-aquatic plants are plants which typically root in water, but emerge above the water surface and get sunlight and CO2 like land-based plants. These are plants that are placed close to the edge of a pond, or on its margins. They will also tend to grow in boggy or waterlogged soil.

These plants are typically in the category of aquatic plants referred to above, commonly known as marginals. Some can cope with permanently waterlogged roots, while some tolerate their roots being submerged only for a period of time.

It is important to make sure that, if you want to place a marginal aquatic plant, or semi-aquatic plant in a pond or water feature, that it can cope with permanent root submersion.

Remember, rooted aquatic plants also need to be placed so that they are at the right depth, and so that their leaves are above water level. And floating plants will be on the surface of the water, not submerged entirely within it.

How Does pH Affect Aquatic Plants?

PH levels can be important, whether we are talking about a garden pond, a water feature, or an aquarium. Carbon dioxide lowers water pH, making it more acidic. So when plants absorb carbon dioxide and remove it from the water, pH will rise. The plants in an aquatic system, therefore, have an impact on maintaining pH balance.

Most natural freshwater features have a pH of between 6 and 8. But water acidification in both fresh and saltwater bodies is a major ecological problem caused by humanity and our emissions. Unpolluted rain should have a pH of 5.6, But most rain has a lower pH than this due, in large part, to fossil fuel emissions and other forms of pollution.

When acidity increases in aquatic systems, it can have a detrimental effect on both aquatic plants and aquatic wildlife. Algae and other non-desirable plant species are more likely to arrive. And aquatic animals will suffer, which in turn throws off the balance in the system and causes more problems for aquatic plants.

Too high an alkalinity is more likely to be a problem in an aquarium than in a garden pond. When the pH in a fish tank rises above 7 (when tap water is too hard, for example, or when the aquatic plants remove too much CO2) then adding CO2 to the system may be necessary.

In a garden pond, pH level is not usually a problem, as long as you make sure that you include plenty of aquatic plants to keep the natural system in balance.

What Are The Best Aquatic Plants For An Aquarium?

Choosing aquatic plants for an aquarium is quite different to choosing aquatic plants for a garden pond or water feature. Aquarium plants need to be tough to cope with changes in water chemistry and temperature in a closed system, and usually need to survive with a lot less light.

Some top plants for a freshwater aquarium include:

  • Amazon sword
  • Anubias
  • Cryptocorynes
  • Java moss
  • Java fern
  • Narrow Leaf
  • Water wisteria
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