Wet air, not a wet cube. Gentle light until the roots show.
How do I take cuttings that root?
GROWER ANSWER
Take healthy shoots from a healthy plant, keep the air around them wet and the light gentle, keep the root zone warm, and then leave them alone. A cutting has no roots, so it can't drink much yet. Everything you do for the first days is about keeping it from drying out while it grows them.
Wet air, not a wet cube.
Start with the plant you cut from
Cuttings root off what the parent plant has stored up. A stressed plant, one that's hungry, pale or still recovering from a problem, gives you weaker cuttings. If she's catching up, give her a week or so of clean, healthy new growth before you cut.
Which shoots: healthy, vigorous ones with a few nodes. Lower branches are fine to use, as long as they're healthy and growing.
Skip anything yellowing, spotted, thin and stretched, or full of flowers.
Plan it. Shoots you top off for height or space can be your cuttings, so topping and taking cuttings can be one job.
Take the cut
Use something clean and sharp. Make one clean cut, and get it into your cube, plug or cloner quickly, because air starts getting into a cut stem right away. Trim off the lowest leaves so nothing sits in the wet, and leave a few leaves up top to work.
Set the cubes or plugs up before you cut, pre soaked and drained, so the cuttings don't sit waiting.
Set the room
A cutting can't drink much until its roots grow. Humid air keeps its leaves from losing water while they do, so the room does most of the work:
Humidity: about 80 to 95% under a dome for the first days. Most home domes won't hold the top of that range, and that's fine.
Light: gentle, about 100 to 200 PPFD at the tops. Unrooted cuttings can't drink enough to keep up with strong light.
Root zone: warm. In a cool room, a seedling heat mat under the tray is the usual way to warm it.
Wet air, not a wet cube
In our experience, this is where most cuttings go wrong. The air around the leaves should be wet. The cube or plug should be moist and drained, never sitting in water. A waterlogged cube has no room for air, and the base of the stem needs oxygen to build roots. Without it, the stem stalls or rots instead of rooting.
Check the cubes by weight, the same way you'd lift a pot. Water them when they've lightened up, not on a schedule.
Step it down as roots show
When roots show at the bottom or the sides of the cube, the cutting can start drinking for itself:
Open the dome a little at a time over a few days, stepping the humidity down toward the seedling range, about 65 to 75%.
Raise the light gradually toward the seedling range, about 200 to 300 PPFD.
Pot it up once the roots are coming out of the cube, and treat it like a seedling from there.
Don't rush the dome off. Pulling it all at once dries out a cutting that's only just started rooting.
If they're not rooting
Look at the room before you blame the cutting. The usual causes:
The cube stays soaked. Let it drain and lighten up.
The light is too strong. Back it off to the gentle range.
The root zone is cold. Warm it with a heat mat.
The air is too dry. Leaves that droop and stay down in a dome that isn't holding humidity are drying out.
The parent plant was stressed. Next round, cut from cleaner growth.
Some cuttings take longer than others, even from the same plant. Give them time before you pull one to look, because every check disturbs the stem.
What not to do
Don't blast them with light. Gentle until the roots show.
Don't keep the cubes dripping wet. Wet air does the job.
Don't cut from a plant that's struggling. Let her recover first.
When it's something else
Starting from seed instead: see My seeds won't pop. How do I start seeds and keep seedlings alive?
Topping for shape and space: see Should I top or LST my plant, and when?
Keep going
Domes, trays, cubes, heat mats and rooting gels: see our seed starting and cloning department.
Healthy cuttings, a steady room, one change at a time. The whole system for a steady grow is written down in the free Stability Playbook. Get the free Stability Playbook
More answers: all grow guides. Every shelf guide and maker feed chart: Grower Resources.