Lotus Root Care Through the Growing Season: Water, Feed and Leaves

The three kinds of leaf, and what they tell you

The first leaves of the season are coiled spears that unroll flat on the surface of the water. These floating leaves mean the rhizome is alive and rooting, but nothing more; the plant is still living off the food in the old segments. Then come the standing leaves, held clear of the water on a stiff stem, at first a few inches up and later two to five feet (60 to 150 cm) high. Standing leaves are the working leaves, and only once several are up is the plant feeding itself and building the crop.

The number and height of standing leaves is the single best progress indicator you have, because everything else is hidden in opaque mud. A plant that reaches midsummer with only floating leaves is too cold, too shaded, too crowded or was planted with a damaged tip, and it will not make a crop that year. A plant with a dozen tall leaves standing well clear of the water is fattening segments underneath.

Late in the season the plant sends up one or two very tall leaves and then stops. That is the signal that the runner has stopped traveling and started swelling, and it is the point at which your feeding stops too.

Never cut a stem under the water

Lotus leaf stems are hollow tubes, and they are the plant's air supply. Air enters at the leaf, travels down the stem and pressurises the whole rhizome, which is what keeps it alive in mud with no oxygen in it. Cut a stem below the waterline and the tube floods. Water runs down into the segment it is attached to, and that segment rots, often taking the growing tip with it.

So remove leaves only above the water, and only when they are already yellow or brown and finished. Leave a hand's width of stem standing above the surface, and let it dry off and collapse on its own. The same rule applies to any accidental damage: if a storm snaps a stem below the surface, cut the remaining stub off above the water immediately rather than leaving a flooded funnel open.

Do not tidy healthy leaves for the sake of appearance. Every standing leaf you remove is food the rhizome does not get, and the crop is made in the last third of the season when the plant is running on exactly those leaves.

Bent or leaning leaves do not need cutting. As long as the leaf is green and the stem is not broken below the surface, leave it alone.

Feeding: heavy, buried and stopped early

Lotus is a hungry plant and the mud in a tub runs out quickly. Feed with aquatic plant tablets pushed deep into the soil, never with anything scattered on the surface or dissolved in the water, which just feeds the algae and turns the tub green.

1. Start when the first standing leaf is up Do not feed at planting or while the plant has only floating leaves. There are no roots to take it up yet and the fertilizer sours the mud around the new tip.
2. Push tablets to the bottom of the mud Work each tablet down with a finger or a length of dowel until it is four inches (10 cm) deep, well away from the growing tip, and close the hole behind it so nothing leaches into the water.
3. Repeat every three to four weeks Use roughly one tablet per gallon (4 L) of soil each time through late spring and summer, or follow the rate on the pack. If the water goes green after feeding, you have used too much or placed it too shallow.
4. Stop about six weeks before dieback Late feeding pushes soft new leaf growth instead of letting the runner swell, and soft late growth is what rots over winter. Once the plant sends up its last tall leaf, feeding is finished for the year.
5. Watch the leaf color between feeds Pale yellow-green new leaves with green veins mean it is hungry. Dark green leaves with brown scorched edges usually mean too much fertilizer too near the surface: top the tub up with fresh water and skip a feed.

Water, heat and keeping the runner in bounds

Keep the water level steady rather than deep. Two to three inches (5 to 8 cm) over the mud in early spring warms fastest and gets the plant moving; raise it to four to eight inches (10 to 20 cm) once the standing leaves are up, so the mud does not dry out on hot days. Letting the tub go dry even once, for even a day, checks growth badly and can kill the tip outright.

Heat is what makes the root fat. Lotus wants a long run of days above 80F (27C) at the water surface, and it does very little below 68F (20C). In a cool summer, keeping the water shallow and the tub in the hottest, most reflective position you have is the only lever you actually control.

From midsummer, check the rim every time you top up. Runners travel outward and will climb the inside wall looking for somewhere to go. Push any runner that has reached the edge gently back down into the mud with your fingers, and make sure no leaf or runner is bridging out of the tub onto wet ground. Algae on the surface is cosmetic and can be lifted off by hand or with a net; it competes for nutrients but does not harm the plant.

Keep a running note through the season of the date the first standing leaf appeared, the date of each feed, and roughly how many standing leaves you have at midsummer. Those three numbers, set beside what you dig up in autumn, tell you next spring whether to feed harder, move the tub into more sun, or plant two weeks later into warmer water.