Choosing marginal pond plants
Choosing and buying pond and marginal plants and how to plant them.
In a well-balanced planted pond, aquatic plants are far more than decoration. They actively support water quality, fish health and the overall visual impact of your water garden.
1. Functional Role of Pond Plants
Aquatic vegetation acts as a natural filtration system. In the same way that garden plants compete with weeds in a flower border, desirable pond plants compete with nuisance algae such as green water and blanketweed for light and nutrients. The stronger and more established your planting, the less opportunity algae has to dominate.
Submerged plants also provide essential spawning areas for species such as goldfish and other ornamental pond fish. Their dense growth offers shelter for fry, protecting them from predators and increasing survival rates.
2. Aesthetic Role of Pond Plants
Plants are equally important for shaping the pond’s appearance. Strategic planting softens hard edges, disguises liner margins and blends the pond naturally into the surrounding landscape.
As a simple design rule:
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Taller marginal plants belong towards the back or rear edges.
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Lower-growing, spreading marginals work best at the front.
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Surface plants break up reflections and add seasonal interest.
With hundreds of aquatic plant varieties available, it is more helpful to understand planting zones than to focus on individual species. Once you understand where plants thrive, you can select varieties to suit your style and local availability.
The Three Main Planting Zones in a Garden Pond
1. Marginal Plants (Shelf Zone)
These are planted on shallow shelves around the pond edge, typically 6–12 inches below the water surface. Marginals provide structure, soften edges and create transition between water and land.
Examples include:
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Water Iris
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Marsh Marigold
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Water Mint
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Sweet Flag
They are essential in achieving a natural pond look.
2. Deepwater and Submerged Plants
Rooted on the pond bottom, these plants grow up through the water column. They are vital for oxygen production and nutrient uptake, helping maintain healthy water conditions.
Deepwater plants such as water lilies also provide valuable surface shade, reducing light penetration and discouraging algae growth.
Submerged oxygenating plants are particularly important in maintaining a biological balance within the pond ecosystem.
3. Floating and Surface Plants
Floating plants sit directly on the water surface and help reduce light penetration, limiting algae growth. They also offer shade and refuge for fish.
However, avoid allowing surface coverage to exceed 50% of the pond area, as this can reduce oxygen exchange.
How to Plant Aquatic Plants Correctly
Most aquatic plants are planted in mesh baskets rather than directly into the pond base. This allows easy repositioning and prevents aggressive spread.
The correct planting method:
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Line a plastic aquatic basket with hessian or foam liner.
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Fill with heavy aquatic loam (never standard garden compost).
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Position the plant securely.
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Cover the soil surface with a generous layer of gravel to prevent clouding.
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Gently lower the basket to the appropriate shelf or depth.
Using proper aquatic soil and gravel topping prevents nutrient leaching and keeps water clear.
Creating a Balanced Planted Pond
A successful planted pond blends function with beauty. Strong planting:
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Competes naturally against algae
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Supports fish spawning and fry survival
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Enhances water clarity
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Softens pond structure
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Creates a visually natural landscape
When planted thoughtfully across all three zones, aquatic vegetation transforms a simple pond into a thriving, balanced water garden.
1. Marginals
These are placed on the shelf and their position in relation to the viewing point is determined by its eventual height. Marginals will produce a variety of foliages and flowers above the water s surface and these include: The many varieties of iris available in the stunning yellow through to a very rich purple. Other taller marginals such as the Sweet Rush (Acoras), Cotton Grass (Eriophorum) and the Reed Mace (Typha).
Lower growing marginals that provide excellent colour include the fiery red Lobelia cardinalis and the vibrant and hardy Marsh Marigold. Great coverage can also be achieved by the similarly flowered Ranunculas.
Two plants which will soon cover bank margins, growing before your very eyes are the rampant Water Forget-Me-Not (Myosotis) and Water Mint (Mentha aquatica). These are excellent in a new pond but must be chopped back regularly to keep them under control.
2. Deepwater plants
These plants will be situated on the pond bottom to produce pad-like leaves on the surface. A host of lilies are available to choose from with the 2 features that are essential to identify before buying being their colour and size. Be sure to choose the colour you prefer (as they are not likely to be flowering at that time) and the size of the overall plant should complement the area of the pond. Pygmy or miniature lilies are quite rare but well worth the extra cost as they do not tend to be as rampant or invasive as the larger lilies.
Water Hawthorn (Aponogeton) is a similar grower to a lily but with more delicate flowers and smaller, elliptical leaf-pads.
Other deep water plants include the group of submerged plants called the oxygenators . Planted to the bottom, they will grow upwards, oxygenating the water and utilising light and nutrients so as to outcompete the unwanted algae and blanketweed.
These should be the first plants to be added to a new pond and include Hornwort (which is quite resistant to grazing by fish) and Water Milfoil. Starwort (Callitriche) and Water Violet (Hottonia) can also perform this vital, functional role for a planted pond.
3. Floating plants
Some floating plants can be very invasive and can be used as a short-term measure to prevent unwanted algae. Duckweed or Frogbit are particularly fast growers and must be netted off regularly to maintain a clear surface. Water Soldiers (Stratiotes) are very hardy plants which hang just below the surface and also perform an oxygenating role.
A balanced combination of plants for all zones within a pond will both transform a pond s appearance and maintain its healthy aquatic environment.
Plants for the bog garden
The beauty about planting a bog garden is that we have complete freedom as to where to place our chosen plants. Bog plants are by their nature tolerant and adaptable and will soon colonise and spread through what is a very favourable and fertile substrate.
You can try to include a graduation in the planting scheme. Those plants that are quite tolerant of drier areas of a bog garden can be planted to the margins where they will blend with the drier terrestrial borders.
Bog Plants
The early flowering Globe Flower (Trollius europaeus) and Marsh marigolds (Caltha palustris) will serve to brighten up the foreground of a bog garden. The Marsh Marigold will soon cover any areas of bare soil with its rampant growth, especially when unhindered by a basket. Further splashes of colour can be added with Primulas, available in many colours and shapes, from the red-hot-poker shaped P. vialii to the more delicate P. bulleyana, both early to flower. A scattering of the more delicate lanterned Frittillaries can also add some movement in a gentle breeze.
A particular fan of the moist conditions is the Arum Lily (Zantedeschia) while the closely related Hosta (H. sieboldiana) will tend to grow quite large, providing generous cover for any amphibian inhabitants. Other plants that can serve as a backdrop include the tufting Cotton Grass and any number of Iris varieties.
The periphery of the bog area can be planted with varieties that will blend in well with any bordering terrestrial vegetation. Possible candidates for this role include the tall and Iris-like Phormium tenax and the spreading Meadowsweet (Filipendula) which may well choose to dip its feet either side of the bog garden. A superb backdrop of ferns (Matteuccia) would complete the effect.
Pond Plants help a pond to become balanced, but what is meant by balanced?
It may take years to achieve a balanced pond and a newly constructed pond may well experience highs and lows in appearance and habitat quality along the journey to becoming established. For example, algae is a common problem in newly constructed ponds. In an artificially maintained pond, the action of a pump, filter and UV system will maintain the clarity and sweetness of the pond water in a matter of days. In a wildlife pond, it is the collective responsibility of the pond flora (plant life) and fauna (animal life) to maintain such a balance. Because you can t rush mother nature, this may take years to achieve. However, having waited and facilitated nature s balancing act, patiently over a matter of months and years, a naturally balanced pond is likely to be more stable in the long term.
If after only a few days, the water turns green, you may be forgiven for having the instinct to drain the pond and start again. This will only prolong the problem as every new pond on the road to becoming balanced has to pass through an unsightly green water stage. This is why if you take a more organic approach, that much patience is required along the way.
A balanced pond is one in which the nutrients and sunlight (which drive the pond) are at the correct level for the flora and fauna present. A newly filled pond turns green because firstly the tapwater may be high in nutrients encouraging plants to proliferate (green water algae) and secondly because there is insufficient established plant life to shade or compete for the sun. So if your pond does turn green, simply concede this first battle, knowing it will eventually fade and that your pond will come through to win the war. Consequently, when considering a conservation pond, probably half of your budget should be set aside for plants. These are your allies in the war to making your pond s ecosystem balance.
Nutrients entering a pond can be a real problem when fighting the battle against algae. As already mentioned, tapwater can be an unwitting source of nitrates and phosphates which can be reduced by using rainwater as a source of water. Other inadvertent sources of nutrients are fish foods which after digestion, can release nutrients into the pond water.
Beware! Invasive Alien Species
Many aquatic plants that are on sale in garden centres are non-native species and have been shown to invade our natural aquatic habitats, taking over where once our more delicate native species thrived.
As a pondkeeper, you can help to conserve the UK s native aquatic habitat by:
1. Not buying any of the following non-native aquatic plants that are already invading the UK s natural aquatic habitats.
Crassula helmsii Australian swamp stonecrop or New Zealand pigmyweed
Myriophyllum aquaticum Parrot s feather
Hydrocotyle ranunculoides Floating pennywort
Impatiens glandulifera Indian (Himalayan) balsam
Azolla filiculoides Water fern
Azolla caroliniana Water fern
Pistia stratiotes Water lettuce
Salvinia molesta Giant salvinia
Crassipes Water hyacinth
Trapa natans Water chestnut
2. Buying native species instead.
Oxygenating plants
Callitriche stagnalis Starwort
Ceratophyllum demersum Hornwort
Eleocharis acicularis Hair grass
Fontinalis antipyretica Willow Moss
Hippurus vulgaris Marestail
Hottonia palustris Water violet
Myriophyllum spicatum Water milfoil
Myriophyllum verticillatum Whorled milfoil
Potamegoton crispus Curly pond weed
Ranunculus aquatilis Water crowfoot
Floating aquatic plants
Hydrocharis morsus ranae Frogbit
Stratiotes aloides Water soldier
3. Do not release any aquatic plants from your pond into natural rivers, ponds or brooks, Compost everything in your own garden.
For more information, consult the Plantlife website: www.plantlife.org.uk
