Gadenin日本語Get the appWhy cuttings, and not seed
Sweetness in stevia is inherited, and it varies enormously between individual plants. A cutting is a clone: the leaf on the new plant tastes exactly like the leaf on the plant it came from. Seed is a lottery played again every year. Once you have found or been given a plant whose leaf is genuinely sweet, cuttings are the only sensible way to keep it.
There is a practical argument too. Stevia is tender and, in most gardens, is treated as an annual or lifted for winter. Rather than nursing a big old plant through the cold months, you can take a handful of cuttings in late summer, root them in a jar on a windowsill, and overwinter small plants that take up almost no space. In spring those become your stock plants.
Take the cutting from a shoot that is not flowering
The best material is a soft, actively growing side shoot from the upper half of the plant, taken while the plant is still vegetative. A shoot that has started to form flower buds is committed to flowering, roots badly, and if it does root, the young plant tries to flower at four inches tall. In practice this means taking cuttings from spring through midsummer, before the shortening days push the plant into bud, or from a plant you have been pinching to keep it vegetative.
- Cut a four inch (10 cm) tip Take the top four inches of a healthy side shoot with a clean blade. Cut just below a leaf joint, because that node is where roots form most readily. Choose a shoot that is firm but still bends without snapping.
- Strip the lower leaves Remove the leaves from the bottom half of the cutting so nothing sits below the water or compost line. Leave two or three pairs at the top. Any leaf left buried rots and takes the stem with it.
- Halve the remaining leaves if they are large Cut the biggest top leaves across by half with scissors. A rootless cutting cannot supply a full canopy, and reducing the leaf area cuts water loss without leaving the cutting unable to feed itself.
- Root in water or in compost Either works. In a glass of water on a bright windowsill, roots show in ten to fourteen days. In compost, dip the cut end in rooting hormone, push it into a fifty-fifty mix of perlite and all-purpose potting mix, and cover with a clear bag.
- Keep it out of direct sun Bright indirect light and 68 to 77F (20 to 25C) is what a cutting wants. Full midday sun on an unrooted cutting cooks it inside a day, however wet you keep it.
Water rooting against compost rooting
Water rooting is easier to judge because you can see exactly what is happening, and stevia takes to it well. The drawback is that water roots are brittle and adapted to being submerged, so they suffer when you transfer them into compost. The fix is to pot up early, as soon as roots are half an inch (1 cm) long, rather than waiting for a big white tangle.
| Method | Time to roots | Strengths | Watch out for |
|---|---|---|---|
| Glass of water | 10 to 14 days | No kit, easy to monitor, high success rate | Brittle roots; pot up at half an inch (1 cm), change the water every two days |
| Perlite and compost | 14 to 21 days | Roots transplant without a check, stronger plants | You cannot see progress; test with a gentle tug after two weeks |
| Pure perlite under a bag | 12 to 18 days | Very little rot, good for a batch | Dries out fast; needs a sealed cover and daily checks |
| Layering a low shoot | 3 to 4 weeks | No detachment shock at all, near certain | Only one or two plants at a time, ties up the parent |
Growing the rooted cutting on
Pot each rooted cutting into a three and a half inch (9 cm) pot of ordinary potting mix and keep it warm and lightly shaded for the first week while the roots take hold. From then on treat it as a young plant: full light, compost kept evenly damp, and no heavy feeding. When it reaches six inches (15 cm), pinch the tip out to force branching, exactly as you would with a seedling.
A cutting taken in late spring will be a usable, harvestable plant by late summer of the same season. A cutting taken in late summer will not give you a crop that year, but it makes an ideal overwintering plant: small enough for a windowsill, and ready to grow away hard as soon as the light returns.
Take more cuttings than you need. They are free, they cost you nothing but a shoot tip you would have pinched off anyway, and having six rooted plants in reserve means one hard frost or one collapsed pot does not lose you the plant.
Keep track of which plant came from where
Cuttings look identical, so label them at the moment you take them, not later. Write the parent plant's name or number, the date you took the cutting and the method you used. When some root in twelve days and others take a month, that record tells you which shoot type and which time of year works in your conditions.
Over a few seasons the most valuable note is the lineage: which original seedling every plant in your garden descends from, and how sweet that line tastes. A stevia clone kept going by cuttings can outlast the gardener's memory, and the only thing that stops you losing track of a genuinely good plant is having written down where it came from.