Creating a Japanese garden with a koi pond: principles, elements, and plants

A Japanese garden is not a collection of “Asian” objects arranged around a body of water. A concrete lantern, three bamboo plants, and a red bridge are not enough, and often produce the opposite of the desired effect. What makes a Japanese garden are rules of composition: asymmetry, restraint, the empty space that highlights the full, and water that seems to have always been there. The good news is that these rules translate very well to an ordinary-sized Belgian garden, and a koi pond is its ideal centerpiece. Here is how to think it through, element by element, with plants that can withstand our damp winters and sometimes dry summers.

The principles of a Japanese garden

Traditional Japanese gardens, whether designed for strolling, tea ceremonies, or contemplation, share a few simple ideas. These matter more than the choice of one object or another.

Asymmetry. Nothing is centered, nothing is mirrored. A round pond in the middle of the lawn with one plant on each side is a formal French garden. In Japan, elements are offset and grouped in threes, fives, or sevens, creating irregular triangles rather than alignments.

Miniaturizing the landscape. The garden evokes a mountain, a river, a shoreline. An upright boulder becomes a peak, raked gravel becomes the sea, and a pine pruned into cloud shapes becomes an old tree clinging to a cliff. Nature is not copied; it is summarized.

Borrowed scenery (shakkei). Incorporate into the composition what lies beyond the fence: a neighbor's large tree, a hedge, a steeple, or a line of hills. In a Belgian housing development, this may simply mean framing the birch at the back of the neighboring plot rather than hiding it.

Empty space. An expanse of gravel, moss or still water is not a surface to be “filled.” It is what gives weight to the elements around it. The most common mistake in Europe is accumulation: every square meter receives a plant or an object, and the garden becomes a catalog.

The path. A Japanese garden is discovered step by step. The path winds around, conceals and then reveals the pond, encouraging visitors to slow down. Even on 150 m², this feeling can be created by running a path behind a planting bed before it opens out onto the water.

The pond at the heart of the garden

In a Japanese garden with koi, the pond is both an aesthetic feature and a demanding living environment. Both considerations must coexist from the design stage onward.

Location. Place the pond where it can be seen from the living area: a Japanese garden is looked at at least as much as it is walked through. Avoid placing it directly beneath large deciduous trees (leaves, complete shade), but allow for partial afternoon shade, which is welcome in summer to keep the water temperature down.

Shape. Irregular contours are the norm: a cloud shape, a stylized Chinese character, or simply a winding shoreline with a projection and a cove. One side may be edged with large stones dipping into the water, another with a pebble beach, and a third with vegetation. This variety of shorelines creates the illusion of a natural body of water.

Dimensions for koi. This is where aesthetics must not take precedence over biology. Adult koi measuring 50 to 70 cm need a substantial volume of water and sufficient depth to overwinter and shelter from herons. As a general guideline, less than 10 m³ is rarely suitable for a small group, with an area at least 1.20 to 1.50 m deep. Planting shelves should remain narrow so they do not reduce the usable volume.

Hidden filtration. A koi pond without serious filtration quickly turns green or develops an ammonia crisis. Filtration (pump, biological filter, UV-C) must be present but remain invisible: a service area behind a non-running bamboo hedge or a wooden screen, buried pipes, and water returning via the waterfall. A bottom drain and a skimmer integrated into the construction make life much easier later on.

Stones, gravel, and lanterns

In Japan, people often say that a garden is first built with stones. They set the structure while the plants grow, change, and sometimes die.

Choose few stones, but beautiful ones. Three characterful blocks, with veins, worn edges, and patina, are better than twenty identical rock-garden stones. Stick to a single geological family for consistency: in Belgium, sandstone, gray limestone, or weathered blue stone work well, as do imported granites in dark tones.

Bury them. A stone placed on the ground looks as though it was brought there. A stone buried one-third of its height looks as though it has always been there. This is the detail that distinguishes a successful composition from a pile of materials.

Group them in triads. The classic composition combines a tall, upright stone, a medium, inclined stone, and a low, flat stone, forming an irregular triangle. Repeat this motif at different scales, varying the orientation.

Gravel. Light-colored, angular gravel 3 to 8 mm in size rakes well and holds patterns. Lay it over geotextile and a compacted foundation layer; otherwise, it will mix with the soil within two seasons. Be careful not to bring it into direct contact with the pond water: fines and limestone from poorly washed gravel will eventually end up in the water.

The lanterns. A stone lantern (tōrō) is placed beside the water, often where the path ends or turns. One is enough in a medium-sized garden. Low, broad-roofed, legged « yukimi » models are designed to be viewed above the water. Molded concrete lanterns age better if you encourage moss by placing them in the shade and brushing them with plain yogurt or milk.

Bridges, stepping stones and waterfalls

Stepping stones (tobi-ishi) are flat stones spaced 10 to 15 cm apart, about one human step from one another. They impose a rhythm and invite you to watch where you are walking, thereby slowing you down. They can cross moss, gravel, or even a very shallow area of water, provided they are perfectly stable on a concrete foundation.

The bridges. A bright red arched bridge is a picture-postcard image; in a private garden, a flat bridge made of dark wood or stone (a simple long slab resting on two supports) is often more appropriate. It crosses the pond at its narrowest point, at an angle rather than perpendicularly. For koi, a bridge has a practical benefit: it creates a shaded area and visual shelter from herons.

The waterfall. Falling water is a central feature of stroll gardens. It also serves as an aerator and filtration return. In the Japanese tradition, the aim is for the waterfall to look as though it emerges from the mountain, between two large side stones, with a perfectly horizontal flat spill stone creating an even sheet of water. A modest, credible waterfall is better than a wall of stacked stones. As a rule of thumb, allow for a flow rate of approximately 1,000 to 1,500 liters per hour for every 10 cm of spillway width to create a continuous curtain, taking the pumping height into account.

Plants suited to the Belgian climate

The Japanese garden relies on a limited number of species, often evergreen, with fine foliage, pruned to maintain clean shapes. Many iconic plants are perfectly hardy in Belgium, provided their soil and exposure requirements are respected.

A few practical tips. Japanese maples hate heavy, waterlogged soils: beside a pond, plant them on a gentle mound rather than at the foot of the bank. Azaleas and pieris need acidic soil; in the calcareous soils found in some regions, prepare large beds of ericaceous soil or choose other shrubs. Running bamboos are a real nuisance near a pond liner: their rhizomes puncture whatever they encounter. Stick to clumping Fargesia.

In the water itself, the Japanese garden remains understated. A few clumps of iris, one or two water lilies, and that's it. With koi, every submerged plant must be in a basket weighted with pebbles, otherwise it will be uprooted or nibbled within a few weeks. Many owners set aside a small planted filtration zone, separated from the main pond by a submerged low wall or supplied by the filtration circuit, to enjoy the vegetation without exposing it to the fish.

Lighting

At night, a Japanese garden takes on a completely different appearance, provided you do not light it like a parking lot. The principle is to highlight only a few elements, leaving the rest in shadow.

• Looking up at a tree: a spotlight placed at the foot of a maple or pine reveals the structure of the branches.
• Grazing light on a feature stone: it highlights the contours and veins.
• Subtle underwater lighting: one or two spotlights in the pond, aimed at the waterfall or beneath the bridge, are enough. Too much light in the water reveals the bottom and equipment.
• Warm light: choose warm white over cool tones or changing colors.

For koi, avoid permanent lighting throughout the night: fish need an alternation between day and night. A timer that switches off around 11 p.m. is a good compromise.

Maintenance

A Japanese garden has a reputation for being demanding. This is true of pruning, much less so of everything else. Here is a typical calendar for a Japanese garden with a koi pond.

The gravel does not need to be raked daily: once a week is enough to keep the patterns clear. Pruning pines into cloud shapes is the real long-term work. It is done over several years, thinning the branches to create layers of foliage. If you do not have the time, choose slow-growing conifers that naturally maintain a compact shape.

Common mistakes

• Too many objects. A lantern, a basin (tsukubai), and a few stones are enough. Buddhas, pagodas, crane statues, and red bridges all together create a themed garden rather than a Japanese garden.
• A pond that is too small for koi. This is the main source of problems: unstable water, stressed fish, and disease.
• Stones placed on the surface rather than buried. They look artificial and, at the water's edge, can tip over.
• Too many plant species. Repeating five to eight species well is better than having thirty different plants.
• Visible filtration. A blue filter at the water's edge ruins the composition; it must be anticipated from the planning stage.

Common case: an existing garden pond, round and surrounded by lawn, that you want to give a Japanese feel. Rather than redoing everything, you can break up the symmetry by widening one bank with a pebble beach, installing a triad of stones on the opposite side, planting an off-centre maple and replacing part of the lawn with raked gravel and moss. The pond remains the same, but the overall impression changes completely.

Inspiration: Japanese gardens to visit in Belgium

Nothing compares with observing a site in person to understand the scale, the role of empty space and the way the stones are placed. The Japanese Garden of Hasselt, in Limburg, is one of Europe's leading examples: its waterfall, pond and cherry trees clearly show how water structures a strolling garden. Belgian arboretums, such as those in Kalmthout and the Meise Botanic Garden, also allow you to see mature Japanese maples, pines and azaleas in context, and choose the varieties you like before planting.

During these visits, take photos of details rather than overall views: the way a stone plunges into the water, the spacing between stepping stones, the height of a lantern in relation to the path. These are the details that will make the difference in your own garden. For the technical aspects of the pond, our guides on building a waterfall and on garden pond lighting usefully complement this overview. If you are planning a stream that meanders before joining the pond, our article How to create a beautiful stream? explains the slopes and flow rates.

Also read

To explore the spirit of Japanese ponds further: Everything you need to know about Japanese ponds, spaces dedicated to relaxation and meditation.

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Frequently asked questions

— What is the minimum size for a koi pond in a Japanese garden?

As a rule of thumb, we rarely aim for less than 10 m³ with an area 1.20 to 1.50 m deep. Koi grow considerably and need volume and stability.

— Can aquatic plants be kept with koi?

Yes, but in weighted baskets filled with pebbles, or in a separate planted filtration zone. Otherwise, the koi will uproot and nibble them.

— Which Japanese trees can withstand the Belgian climate?

Japanese maples, pines (black, Scots, densiflora), flowering cherry trees and crenate holly are hardy here, provided their soil and exposure requirements are met.

— How many lanterns are needed in a Japanese garden?

One is sufficient in most private gardens, placed by the water's edge or at a bend in the path. Accumulating objects detracts from the intended effect.

In summary

• A Japanese garden is based on principles: asymmetry, empty space, borrowed scenery and movement through the garden.
• The koi pond is central, but its requirements (volume, depth, filtration) take precedence over aesthetics.
• Few stones, buried and grouped in triads; a single lantern; gravel laid on geotextile.
• Hardy plants in Belgium: pines, Japanese maples, azaleas, crenate holly, ferns, mosses, irises.
• Warm, low-angle and limited lighting, switched off at night to maintain the fish's rhythm.

Last updated: October 3, 2026.