Water Lilies and Oxygen Plants for a Small Pond

Why every small pond needs a water lily

A water lily is the heart of any pond. The flowering floating leaf provides colour, shade and protection for fish and underwater life. But a water lily alone is not enough. You also need oxygen plants: fully submerged plants that keep the water clear and produce oxygen. Without both, your pond will clog with algae within a season.

A small pond (1 to 4 square metres, 60 to 80 centimetres deep) demands careful plant selection: water lilies and oxygen plants in the right ratio, proper baskets and the correct planting depth for each species. Not sure how a pond corner would look in your own garden? On gardenworld.app you can see it first in a preview of your own garden. This article shows you exactly how to get it right.

Water lilies: two types, two depths

Water lilies are not all the same. There are two main groups: tropical water lilies (for warmer climates and larger ponds) and hardy water lilies (for our climate). For a small pond in the Netherlands or Belgium, you always choose a hardy type.

Hardy water lilies

Depth: 40 to 80 centimetres. Smaller varieties grow better in shallow water, larger ones prefer deeper water.

Flowers: White, pink, red or yellow. Many varieties, from 6 to 15 centimetres in diameter.

Leaf shape: A round floating leaf that can grow as large as a palm or bigger, depending on the variety.

What to choose for a small pond: Nymphaea 'Marliacea Chromatella' (yellow, compact), Nymphaea 'Pygmaea Alba' (tiny, white), Nymphaea 'Attraction' (red, needs a little more space).

Avoid large-growing varieties such as Nymphaea 'Gladstoniana' or 'Gonnere' in small ponds: they become far too big and take over completely.

Tropical water lilies

Better suited to warmer climates or a pond in a greenhouse. In the Netherlands and Belgium they do not survive winter without protection. Unless you bring them indoors in October, you buy new ones every year.

For a small pond in our climate: not recommended.

Oxygen plants: the backbone of clear water

Oxygen plants grow completely underwater. They consume nutrients, especially nitrogen, and release oxygen. This stops algae from getting a foothold.

Quantity per square metre: two to three bunches per square metre of water surface. One bunch is a cluster of 5 to 10 stems.

Depth: 30 to 80 centimetres, depending on the species.

Best species:

• Water violet (Hottonia palustris): fine foliage, flowers pale lilac in May, good for small ponds. 40 to 60 centimetres deep.
• Rigid hornwort (Ceratophyllum demersum): rootless, very effective against algae, also grows in shade. 40 to 80 centimetres.
• Bladderwort (Utricularia vulgaris): fine bladders, keeps pond water healthy, a somewhat weaker grower.
• Canadian waterweed (Elodea canadensis): fast growing and very effective, sold legally at every garden centre. 40 to 80 centimetres.
• Dwarf reedmace (Typha minima): narrow, not suited to dense planting in a small pond. Better as a marginal plant.

Note: never buy or plant curly waterweed (Lagarosiphon major) or Carolina fanwort (Cabomba caroliniana). Both are on the EU list of invasive alien species and have been banned from sale, transport and release since 2016. Canadian waterweed (Elodea canadensis) sometimes grows so fast you need to thin it yearly, which is simply a sign it is thriving.

Floating plants: extra breathing room

Alongside oxygen plants you can use floating plants. These drift on and around the water surface.

Duckweed and water fern: tiny, fast growing and often free from fellow pond owners. They cover the water surface quickly, so keep them in check, though they do filter nutrients well.

Fairy fern (Azolla filiculoides): fine, reddish brown in autumn, grows mainly in warm weather. Note that this species can cover a pond completely within weeks.

For a small pond: limit yourself to a handful of plants, otherwise the water surface disappears entirely under green.

Baskets and substrate

Water lilies and oxygen plants do not grow in ordinary soil in the pond. They sit in specially made baskets.

Water lily basket

Size: for small water lilies 20x20x20 centimetres. Larger varieties 30x30x25 centimetres.

Substrate: clay or pond clay. No flower compost, no peat. Clay holds nutrients and does not leach out.

Planting hole: fill the basket two thirds with clay, plant the water lily, fill around the roots with more clay. Not too deep: the crown of the water lily should sit just above the clay.

Top layer: lay a layer of white gravel (2 to 3 centimetres) on the clay. This stops fish digging up the basket and clouding the water with clay.

Oxygen plant bundles

Oxygen plants need no basket. You tie them into bunches with plant weights, available at every garden centre, and lower the bunch to the correct depth.

Alternative: some pond keepers use small pots filled with clay instead. Also good, and less visible.

Planting depth by species: getting it right

Pond depth is not a guessing game. Each species has its own preference.

Water lily: 40 to 80 centimetres

Larger varieties prefer deeper water, smaller ones can be shallower. Do not plant a water lily deeper than necessary: the shallower it sits, the faster it grows and flowers.

Measuring guide: measure from the pond bottom to the water surface. Place the basket so the crown of the plant sits roughly 5 to 10 centimetres below the surface.

Oxygen plants: 30 to 80 centimetres

Depends on the species and its vigour. Water violet prefers shallower water (40 to 60 cm), Canadian waterweed grows well deeper too (60 to 80 cm).

Floating plants: no depth needed

They float. Simply place them loose on the water.

Plant quantity per square metre

This is the golden rule that many beginner pond owners miss.

Water lilies: at least one per two square metres. In a 4 square metre pond: two water lilies. They need room to spread their leaves without shading each other.

Oxygen plants: two to three bunches per square metre. This keeps the water clear without an algal bloom.

Floating plants: one to two plants at most in a 4 square metre pond.

Too many plants means cloudy water and an oxygen shortage lower down. Too few means the algae win.

Plant in spring, maintain through summer

The best time to install water lilies and oxygen plants is May to June, once the water warms up, at least 12 to 15 degrees.

Do not plant them in October or November: they no longer have enough warm days left to root before winter.

Set the plants out in May, and by July you will see the first flowers. Oxygen plants start working straight away.

In June: check three to four weeks after planting. Is everything growing well? Is everything at the right depth?

In July and August: maintenance: remove dead water lily leaves, thin Canadian waterweed once it gets too dense.

Winter: what does a water lily do?

Water lilies go dormant in October and November. The stem dies back, and the crown withdraws into the silt on the bottom. This is completely normal.

What to do:

1. Leave dead leaves floating or remove them gently, do not scrub them, just lift them out.
2. Make sure the pond water does not freeze over completely. In frost: push a stick through the ice and remove it daily, or use a pond heater in severe cold.
3. Oxygen plants die back above water, but the roots survive in the silt.
4. No feeding between October and March.

In April, as the water warms, water lilies and oxygen plants start growing again. You will see the first green in May.

Keeping the water clear

Here is the balance. Oxygen plants and water lilies only cooperate when the ratio is right.

Green algae: usually too few oxygen plants. Plant more.

Silt build-up: too much organic matter, such as dead leaves and leaf fall. Remove silt every year. Do not empty the pond completely, but take it down to about 10 centimetres.

White cloudiness: usually a temporary bacterial bloom. Add an extra oxygen plant.

Check regularly: look at your pond once a month. Is everything growing well? Is the balance right? Is anything suffocating underwater?

Dwarf grasses around the pond

Around your small pond you can plant low-growing grasses. These prevent erosion and look attractive.

Good for small ponds:

• Japanese sedge (Carex oshimensis 'Evergold'): soft, low, evergreen.
• Blue fescue (Festuca glauca): bluish colour, compact.
• Japanese blood grass (Imperata cylindrica 'Red Baron'): red in autumn.

Do not plant them right at the water edge, but 20 to 30 centimetres back. They do not like wet feet.

Varieties for an extra small pond

Do you have less than 2 square metres of water? Then choose the smallest water lily varieties, bred specially for tubs and mini containers.

Nymphaea 'Pygmaea Helvola': yellow-orange flowers, leaves speckled with brown, one of the smallest hardy water lilies available. Suits a depth of just 30 centimetres.

Nymphaea 'Perry's Baby Red': deep red flowers on a compact plant, suited to a basket as small as 20x20 centimetres.

Nymphaea 'Froebelii': wine red flowers, a classic among the small varieties, grows well at 30 to 50 centimetres.

All of these varieties are hardy in zone 7 to 8 (the Netherlands and Belgium).

Step by step

Step 1: Prepare the pond

Measure the depth and surface area. Check what is already living in the pond, such as fish or old plants. Make sure the water is clean and free of debris.

Step 2: Fill the water lily basket

Fill the basket two thirds with pond clay, place the water lily in it, fill around the roots with more clay, and add a gravel layer on top. Lower the basket carefully into the pond.

Step 3: Place the oxygen plants

Tie the bunches together with plant weights. Lower them to the correct depth: water violet 40 to 60 cm, Canadian waterweed 60 to 80 cm.

Step 4: Add floating plants

Place water fern or duckweed gently on the water. A handful per 4 square metres is enough.

Step 5: Monitor and maintain

Check weekly during the first month to see that everything is growing and sitting at the right depth. After that, maintain per season: remove dead leaves and thin dense oxygen plants in July and August, and prepare the pond for winter in October and November by removing silt and providing an ice hole.

Frequently asked questions

Can I plant a water lily directly in pond clay without a basket?

No. Without a basket the plant grows uncontrollably, the root system becomes unwieldy and you keep disturbing the bottom. A basket is essential.

How long before my water lily flowers?

Four to six weeks after planting, provided the water is warm enough, at least 15 to 18 degrees. The first flowers are small, later ones get larger.

What do oxygen plants feed on?

Nitrogen, phosphate and potassium from the water. These come from leaf fall, fish waste and other pollution. In a healthy small pond, extra feeding is usually not necessary.

Does my pond need winter preparation?

Yes. Gently remove dead leaves and silt, leaving the roots in place, provide an ice hole, and do not let strong winter sun heat the water, which raises the algae risk.

Can I still plant a water lily in August?

That is too late. The water is still warm, but the plant no longer has time to root and prepare for winter. Wait until May of the following year.

See it in your own garden first

Want to see how water lilies and oxygen plants fit into your own garden design? Upload a photo of your garden to gardenworld.app, view a free sample design with water lilies and oxygen plants. The sharp image with the full plant list costs 7.99 euros, a one-time payment, no subscription.