There is something quietly grounding about a Japanese garden. The raked gravel, the moss, the careful balance of stone and space — it all invites a slower breath. But a full-scale version asks for a lot: space, budget, and decades of patience. A tray garden gives you the same feeling in something you can carry with two hands and set on a windowsill. It is miniature gardening at its most forgiving, and it works beautifully in a British courtyard, balcony or bay window. Here is how to build one properly.

Choosing the right tray and the right spot

Start with the container, because it sets the scale for everything else. Look for something shallow and wide: 30–45cm long and 6–10cm deep is a comfortable size. Unglazed terracotta saucers, slate cheeseboards, old seed trays and shallow wooden boxes all work. If your tray has no drainage holes, you are effectively making a shallow pond garden, which is fine — but you must water with restraint. If you plan to leave it outdoors, drill one hole in a corner and cover it with a scrap of fine mesh so grit does not wash out.

Position matters more than most people expect. Japanese gardens are gardens of shade and edge, not blazing sun. A spot that gets morning light and afternoon shelter suits moss and small conifers best. On a patio, tuck it against a north- or east-facing wall. Indoors, a bright windowsill away from harsh midday sun is ideal, though you will need to mist more often.

Gravel, grit and the art of the rake

Use horticultural grit or pea gravel in the 3–6mm range — limestone, granite or a plain grey quartz. Avoid anything brightly coloured or polished; aquarium gravel reads as plastic and ruins the illusion. Spread it 2–3cm deep over a thin layer of soil, and keep a 1cm gap between gravel and the tray rim so nothing spills.

For raking, a small bonsai rake is lovely but not essential. A cheap metal fork with the tines bent sideways works, as does a cocktail stick dragged through damp grit. Rake only when the surface is dry; mist lightly afterwards to settle the lines. Classic patterns are either concentric circles around a central stone, or long flowing curves that suggest a stream moving between islands. Keep lines 1–2cm apart and vary the direction between sections so the eye keeps travelling.

Building moss mounds that actually survive

Moss is the heart of the composition. Gather it from between paving slabs, on shaded walls or along a damp kerb — it transplants far better than anything bought. Irish moss (Sagina subulata) is not a true moss but looks convincing and knits together quickly.

• Shape a dome of soil and compost, 3–5cm high, and damp it thoroughly.
• Press sheets of moss over the dome, overlapping the edges like tiles.
• Pin them down with hairpins or short lengths of bent wire until rooted.
• Keep in shade and mist daily for three weeks, then gradually reduce.

Always use rainwater rather than tap water. The limescale in most UK mains supplies will leave chalky deposits on moss and gravel within weeks, and it is very hard to remove afterwards.

Placing stones — a handful goes a long way

Three or five stones, never four. Odd numbers feel natural because they resist symmetry and invite the eye to wander. Choose weathered slate, sandstone or granite with a little character, and avoid anything shiny or perfectly round.

Bury each stone roughly a third into the gravel so it looks as though it has always been there. Give one tall, upright stone the role of a mountain, a flatter one the role of an island or a shore. Leave the largest gap of open gravel on the side where you want the viewer to rest their gaze. That emptiness is as deliberate as any plant.

Trees, ferns and the question of scale

Think of your tray as a landscape a kilometre wide, and pick plants that behave as though they belong to that scale. Slow, compact and fine-leaved is the rule.

• Dwarf conifers such as Chamaecyparis obtusa 'Nana Gracilis' for a cloud-pruned tree shape.
• Japanese holly (Ilex crenata) or box for neat clipped mounds.
• Black mondo grass (Ophiopogon planiscapus 'Nigrescens') for dark contrast at the edge of gravel.
• Miniature hostas and small ferns for a damp, green corner.

Trim with sharp scissors rather than shears, pinching out growth to keep a natural silhouette. A single well-placed tree with an open, airy shape is worth more than five crowded ones.

Keeping it alive through a British year

Water little and often with a fine rose or a mister — a flooded tray drowns roots and clouds the gravel. Feed very sparingly from April to August, using half-strength liquid feed once a month at most; these plants are growing in a few centimetres of soil and will not thank you for more.

Rake the gravel once a week; it takes two minutes and is the most meditative part of the whole hobby. Trim moss back if it creeps over stones, and pull out any weed seedlings by hand while they are small. In winter, lift the tray into a cold greenhouse or against a sheltered wall if you have used anything tender, and check that drainage holes are clear before a hard frost. Algae on the gravel is a sign of constant wet, so improve airflow and cut back on watering.

Give it a season and the tray will start to look settled, as though it had been there for years. That, in the end, is the whole point.