Gadenin日本語Get the appWhy water rooting works so well here
Most cuttings are a gamble in water, rotting as often as they root. Impatiens are the exception, and they are close to foolproof. The stems are soft, hollow and full of water already, they carry no woody tissue to work through, and they are primed to make roots from any leaf joint. A shoot stood in a glass of water on a kitchen windowsill puts out visible white roots in five to ten days and is ready to pot in two weeks, at essentially a hundred per cent success. This is the easiest propagation any gardener will ever do and it is the reason people keep the same plant going for years.
It also solves the real problem with impatiens, which is that they have zero frost tolerance and die in a single night. You cannot overwinter them outdoors anywhere that freezes. What you can do is take cuttings in late summer, root them in a glass, grow them on a windowsill through the cold months, and put out well established young plants as soon as the frost risk passes, weeks ahead of anything you could buy.
It is worth doing this deliberately with any plant that has performed well, particularly a New Guinea type that has stayed healthy through a summer when the common bedding kind around it succumbed to downy mildew. A cutting is genetically identical to the parent, so you keep the exact color and the exact vigor, which seed will not give you.
- Take a shoot four to six inches (10 to 15 cm) long Choose a healthy non flowering shoot tip from the current season's growth. Cut just below a leaf joint with clean scissors or a sharp knife.
- Strip the lower leaves Remove every leaf from the bottom two thirds of the stem, leaving three or four at the top. Any leaf sitting under water fouls the water within days.
- Pinch off flowers and buds Take off every open flower and every visible bud. The cutting has no roots to support them and they simply drain energy that should go into rooting.
- Stand it in a glass of room temperature water Use enough water to cover the bottom inch or two (3 to 5 cm) of bare stem. Three or four cuttings per glass is fine, as long as no leaves are submerged.
- Put the glass in bright indirect light A windowsill out of direct sun is ideal, at 65F to 75F (18C to 24C). Direct sun heats the water and cooks the stem bases.
- Change the water every two or three days Fresh water is the whole trick. Water left to go cloudy is where cuttings rot, and this is the only thing that commonly goes wrong.
- Pot up at one to two inches (2.5 to 5 cm) of root Wait for a few roots at that length rather than a big tangle. Long water roots are brittle and adapt to compost poorly.
Moving water roots into compost without a check
Roots grown in water are structurally different from roots grown in compost: they are thicker, whiter, more brittle and adapted to being surrounded by water rather than by particles. If you pot a cutting with four inches (10 cm) of water root into dry compost and treat it normally, most of those roots die and the plant sulks for a fortnight while it grows a replacement set. That is why the timing matters and why you pot at one to two inches (2.5 to 5 cm) rather than waiting for a spectacular root system.
Pot into a three inch (8 cm) pot of ordinary all-purpose potting mix, making a hole with a pencil deep enough to take the roots without bending them, then firming gently around the stem. Water it in thoroughly and keep the compost distinctly damper than you would for an established plant for the first ten days, which lets the water roots keep functioning while the new ones form. After that, revert to normal watering.
Expect a few days of drooping straight after potting. This is the same dramatic wilt as always and it resolves once the roots take hold. Keeping the new plant out of direct sun for the first week and covering it loosely with a clear bag for the first three days both help, though neither is essential. Do not feed for the first two weeks; a rooted cutting in fresh compost has everything it needs, and feeding a plant that cannot yet take it up does nothing useful.
| Method | Time to roots | Reliability | Best used for |
|---|---|---|---|
| Glass of water on a windowsill | Five to ten days | Very high | Any number of cuttings, no equipment |
| Directly into damp compost | Ten to fourteen days | High | Skipping the transfer step altogether |
| Compost under a clear bag | Seven to twelve days | High | Dry indoor air in winter |
| Cuttings taken in cold weather | Three weeks or more | Low; many rot | Avoid; take them while it is still warm |
| Sowing seed indoors | Fourteen to twenty one days to germinate | Moderate; needs warmth and light | New colors, large numbers cheaply |
Overwintering the young plants indoors
Take your cuttings in late summer, while the weather is still warm and at least a fortnight before your first expected frost. Cuttings taken in warm conditions root in a week; cuttings taken in the cold, damp fortnight before a frost sit still and rot, which is the single most common failure. Do it too early rather than too late.
Through the winter the young plants want the brightest windowsill you have, cool rather than warm, and much less water than they took outdoors. A south or west facing window is right in winter, when the light is weak and the sun is low. Let the top half inch (12 mm) of compost dry before watering, because a small plant in low light with cool roots in constantly wet compost rots at the base. Feed once a month at quarter strength, or not at all, since you want a compact plant rather than a growing one.
They will stretch anyway in short days. Pinch the tips out whenever a shoot gets long and leggy, which keeps the plant bushy and gives you more cutting material. By late winter one plant will have produced enough shoots to take another round of cuttings, and that second round is what turns a single overwintered plant into a dozen for spring.
Note which parent plant each batch of cuttings came from and how that parent performed. After a season or two you will be carrying forward only the ones that stayed clean and flowered hardest, which quietly improves the whole planting without you buying anything.
Growing from seed, and the seed pods that fire
Seed is the other route and it is worth it if you want large numbers or colors you cannot buy as plants. Sow indoors ten to twelve weeks before your last expected frost. The seed needs light to germinate, so press it onto the surface of damp compost and do not cover it. Keep it at 70F to 75F (21C to 24C) and expect seedlings in fourteen to twenty one days, which is slow enough that people give up on them too early.
Impatiens seedlings are small, slow and prone to damping off, so use fresh compost, water from below rather than over the top, and give them as much light as you can from the moment they emerge. Transplant into plugs at the first true leaves, handling them by a leaf and never by the stem, then grow on cooler and bright. Pinch the tip once at around three inches (8 cm) tall to get a branched plant.
You can also collect your own seed, and the plant makes this memorable. The ripe pods are swollen and translucent and burst explosively at the slightest touch, flinging seed several feet, which is where the name busy Lizzie's relative touch me not comes from. To collect any, cup a pod in a closed hand or slip a small paper bag over it before you touch it. Note that seed saved from a hybrid plant will not come true, so the colors you get will be a mixture, and any plant grown from seed of a common bedding type carries the same vulnerability to downy mildew as its parent.