Short answer
Yes. Cannabis cuttings root in plain water, usually in 10–21 days, though less evenly than in plugs or an aeroponic cloner. Keep the water dark, 20–24 °C (68–75 °F), changed every 2–3 days, and transplant at 2–5 cm of root. Grower practice.
Why
Cannabis roots readily, so a cut stem in water will often form roots without any medium.
Oxygen is the limit. Still water holds little oxygen and loses more as it warms; oxygen management is central to keeping Pythium out of hydroponic roots [3].
Warm, stagnant water breeds rot. Pythium and Fusarium both infect cannabis roots in hydroponic systems [1], and a brown, slimy stem base in a glass is the same problem.
Air in the root zone helps rooting in any medium. In one cannabis trial, cuttings in an airy peat-perlite mix rooted best, while rockwool held at full water capacity, with less air space, rooted worst [2].
Water roots are a different shape. They are thick and brittle and must regrow fine roots once moved to soil or coco.
The numbers
| Item | Target |
|---|---|
| Water temperature | 20–24 °C (68–75 °F) |
| Water change | Every 2–3 days |
| Depth | Bottom 3–5 cm (1–2 in) of stem only |
| Light | 50–150 µmol/m²/s, 18–24 h |
| Time to roots | ~10–21 days |
| Transplant at | 2–5 cm (1–2 in) roots |
What to do
- Use a dark or foil-wrapped glass so algae don't grow.
- Fill with clean, room-temperature water; add an air stone if you have one.
- Stand the fresh-cut stem 3–5 cm deep; keep leaves dry.
- Change the water every 2–3 days.
- Pot into a light, moist mix at 2–5 cm of root, then keep humidity high for 3–5 days.
Common mistakes
- Clear glass in a sunny window.
- Never changing the water.
- Leaving roots to grow 15 cm long before potting.
- Submerging leaves.
Related
- Full article: Clone-only cuts and how to preserve them
- Best medium for rooting clones · When to transplant clones
- Root rot (Pythium)
- Terms: aeroponics · dissolved oxygen
