Gadenin日本語Get the appWhy a container suits this plant so well
Two things about water dropwort make container growing the obvious choice. It needs its roots permanently saturated, which is difficult to guarantee in an open bed but trivial in a pot standing in a tray of water. And it runs across wet ground on stolons that root wherever they touch, which makes an open planting into a spreading patch and makes a raised container into a self-contained crop you can see the edges of.
There is a safety argument too. A crop in a labeled pot on a hard standing is unambiguously the plant you bought and put there. Given that this plant's wild relatives are seriously poisonous, growing it in an obvious container rather than as a patch in a damp corner removes any chance that a household member confuses it with something that arrived by itself.
The pot and the tray
Use a wide shallow pot rather than a deep one. The plant roots in the top few inches and spreads sideways, so a 12 inch (30 cm) wide pot that is 8 inches (20 cm) deep grows far more than a narrow pot of the same volume. Ordinary drainage holes are fine because the pot will be standing in water anyway; a pond basket lined with hessian works equally well.
The tray matters more than the pot. A standard plant saucer holds half an inch and boils dry by lunchtime on a hot day. Use a washing-up bowl, a mortar tub, a solid seed tray with no holes, or any watertight container that will hold 2 to 3 inches (5 to 8 cm) of water around the base of the pot. Deeper water heats more slowly and buys you a margin of a day or two if you are away.
| Component | What to use | Why |
|---|---|---|
| Pot | 12 inch (30 cm) wide, 8 inch (20 cm) deep, with drainage holes | The plant roots shallow and runs sideways |
| Tray | Watertight, holding 2 to 3 inches (5 to 8 cm) of water | A saucer dries out in a single hot day |
| Compost | Heavy loam based mix, no bark chunks, firmed down | Light peat or bark mixes float and break up under water |
| Top dressing | Half an inch (1 cm) of coarse grit | Holds the surface down and keeps the water clear |
| Position | Full sun in cool climates, afternoon shade where summers are hot | Warm roots plus hard sun give tough, harsh leaves |
Filling and planting the pot
Use a heavy loam based compost, not a light multipurpose mix. Bark and coarse peat float out of the pot the first time you flood it and then drift around the tray. Fill to within an inch (2 to 3 cm) of the rim, firm it down properly with your knuckles, and top with a shallow layer of grit which stops the surface clouding the water every time you fill.
Plant three small plants or three rooted stems into a 12 inch (30 cm) pot, spaced evenly, crowns level with the surface. Stand the pot in the empty tray, water from above until it runs through, then fill the tray to 2 inches (5 cm). Cut the tops back by half at planting so the plants push new shoots from the base rather than trying to hold up the growth they arrived with.
- Firm the compost hard Loose compost slumps and floats once flooded, leaving the crowns sitting proud with their roots exposed. Press it down until it feels like garden soil, not like a fresh bag of potting mix.
- Set the crowns level with the surface Not buried. A crown permanently under water in warm weather rots at the collar. The roots want to be flooded, the growing point does not.
- Grit the surface before flooding A shallow layer of coarse grit stops compost washing up into the tray water and keeps it clear enough that you can see the water level at a glance.
- Fill the tray and check it in a day A newly filled pot absorbs a surprising amount overnight. Top the tray back up the following morning and again the day after.
The routine once it is growing
In a container the whole job comes down to keeping the tray full and cutting the pot back regularly. Top up when the water drops below an inch (2 to 3 cm), which in hot weather means daily. Through hot spells, tip the tray out and refill with cold water rather than topping up, because water standing warm for weeks turns sour and rots the lower stems. In cold weather reduce the tray to a shallow film and leave it.
Cut the whole pot down to 2 inches (5 cm) every three to four weeks in the growing season, and feed at half strength after each cut. Two pots cut a fortnight apart give you a continuous supply. Skim off any leaves that fall into the tray, and once a season scrub the tray out properly, because a film of algae on the inside is the first sign that the water is being topped up rather than changed.
| Symptom | Cause | Fix |
|---|---|---|
| Leaf edges browning within a day | Tray ran dry | Refill immediately; use a deeper tray |
| Lower stems brown and slimy | Warm stagnant water | Empty the tray, scrub it, refill cold and change weekly in heat |
| Compost floating out of the pot | Light bark or peat mix | Repot into a loam based mix and grit the surface |
| Pale narrow leaflets | Underfed after repeated cutting | Half strength liquid feed after every cut |
| Stems long, hollow and harsh | Left too long between cuts, or heat | Shear to 2 inches (5 cm) and shade the tray |
| Stolons hanging over the rim into other pots | Normal spreading habit | Cut them at the rim or peg them into a second pot |
Winter, propagation and what to note down
A pot outdoors comes through cold winters as roots and crowns, and in mild regions it keeps producing pickable leaf all winter, slowly. Reduce the tray to a shallow film so the pot is not sitting in a solid block of ice, stop feeding, move it against a wall out of drying wind, and pick lightly. In a cold-winter region, a pot brought into a cool bright room and kept in a full tray gives small cuttings through the coldest months.
Propagating is free and takes minutes. Cut a stolon into lengths with two or three nodes each, lay them flat on the wet surface of a second pot, weight them down with pebbles, and keep the tray full. They root in a week or two in warm weather. Worth noting in your records: the date each pot was planted, the date of each hard cut, and how long regrowth actually took at that time of year. After one season those regrowth intervals let you set a cutting rota that never leaves you short.
Never tip an old pot or its trimmings into a pond, ditch or stream margin. Every node in that compost is a viable plant, and escaped water dropwort is difficult to remove from a waterway.