Gadenin日本語Get the appWhy a bed will not do
Lotus fattens its rhizome in mud that stays flooded from spring until the leaves die back. It is not a plant that merely likes wet feet. The rhizome is a chain of air-filled chambers connected to the hollow leaf stems above the water, and the whole plant breathes through that column. Soil that drains, even slowly, lets air into the mud, and in aerated soil the runner stays thin and stringy instead of swelling into the fat segments you want to eat.
So the home version of a paddy is a container with no way out for the water: a stock tank, a half barrel with a liner, a mortar mixing tub, a food-grade drum cut down, or a purpose-made pond planter. Anything watertight, rigid and stable when full will work. What you are building is six to eight inches (15 to 20 cm) of heavy mud with four to eight inches (10 to 20 cm) of water standing permanently on top of it.
If your container has drainage holes, seal them from the inside with a bolt and rubber washers or a patch of pond liner and marine sealant. A tub that seeps loses both water and warmth, and the mud goes half-dry by midsummer.
Size: width beats depth
The runner grows horizontally, so the harvest is set by how far it can travel before it hits a wall. When it reaches the side it turns, and every turn produces a bend and a short segment rather than a long straight one. A wide shallow tub therefore beats a narrow deep one of the same volume every time.
Round containers give a better crop than square ones because the runner circles the wall instead of jamming into a corner. Whatever you choose, it must be stable and it must be positioned before you fill it: a 24 inch (60 cm) tub of wet mud and water weighs several hundred pounds and cannot be moved once made.
| Container width | Soil depth | Water above soil | What to expect |
|---|---|---|---|
| Under 18 in (45 cm) | 6 in (15 cm) | 3 in (8 cm) | Leaves and possibly flowers, but thin coiled roots. Too small for a crop. |
| 24 in (60 cm) | 6-8 in (15-20 cm) | 4-6 in (10-15 cm) | The practical minimum for edible segments from one rhizome. |
| 36 in (90 cm) | 8 in (20 cm) | 6 in (15 cm) | Comfortable. Several fat segments and room for the runner to stay straight. |
| 48 in (120 cm) or more | 8-10 in (20-25 cm) | 6-8 in (15-20 cm) | A real crop. Warms slowly in spring but holds heat well in late summer. |
Soil: heavy, plain and boring
Use the heaviest mineral soil you can get. Clay loam, plain subsoil topsoil, or unamended garden soil from a bed that has not been heavily composted is ideal. It should feel dense and slightly sticky when wet, and it should stay put when you flood it.
Do not use bagged potting mix, and do not add bark, coir, peat or compost. Those materials float, so half of your soil ends up on the surface and blows away, and the ones that do sink rot underwater, souring the mud, blackening it and stripping the oxygen the young roots need. A tub that stinks of sulfur in early summer almost always has organic matter in the mix.
Aim for a smooth mud with no stones and no lumps. Wet the soil in a barrow or in the tub itself and stir it to the consistency of thick porridge, then leave it to settle for a day before planting. Settling first matters: soil that slumps after planting swallows the growing tip.
Siting and topping up
Put the tub where it gets at least six hours of direct sun, and preferably eight. Lotus fattens its rhizome on heat, and a container in half shade produces leaves all summer and pencil-thin roots in autumn. Hard standing that reflects warmth, against a south-facing wall in the northern hemisphere or a north-facing one in the southern, is better than a lawn.
Water level drops fast once the leaves are up, because tall standing leaves transpire hard and the surface is fully exposed. In high summer expect to top up every two or three days. Add water gently down the side of the tub rather than onto the mud, and use water that has stood in the sun where you can, since a slug of cold tap water can check growth on a hot day.
Keep a simple note of the fill line, the topping-up frequency through the season, and how many hours of direct sun the spot actually gets at midsummer. Sun hours are almost always overestimated, and comparing last year's note with this year's harvest tells you quickly whether the tub needs to move.
Never sink the container into a pond, a bog garden or a wet lawn, and keep its rim several inches above the surrounding ground. Lotus escapes through any overflow and colonises open water permanently.