Can I root cuttings in a jar of water?

Water rooting is genuinely useful and slightly oversold. It is easy, needs nothing, and lets you watch what is happening, which makes it an excellent way to learn. But water roots have no root hairs and a different structure from soil roots, and the plant has to grow a second set once it is potted. That transition is where the losses are.

What you'll need

• A clean jar or glass
• Fresh water
• Small pots and compost for the transfer
• A clear bag for the transfer stage (optional)

Step by step

1. Pick a plant that suits the method.Mint, willow, pelargonium, coleus, basil, tradescantia, busy lizzie, pothos, philodendron, begonia and many soft-stemmed houseplants root in water readily. Woody shrubs, lavender, rosemary and most conifers do not — they rot.
2. Take the cutting the same way you would for compost.A non-flowering shoot about 100mm long, cut square just below a leaf joint, with the lower leaves removed so nothing is under the water.
3. Use a narrow clear container.It holds the cutting upright and lets you see the roots. Clear glass grows more algae than opaque, but being able to watch is most of the appeal.
4. Keep only the bottom 20 to 30mm submerged.Deep immersion rots the stem. One node under the water is enough — that is where the roots come from.
5. Change the water every two or three days.Standing water goes stale and low in oxygen, and that is what turns the stem to slime. Fresh water at room temperature, and rinse the jar.
6. Bright, indirect light and normal room warmth.Direct sun heats the water and grows algae. A north or east window is ideal.
7. Pot it up early — this is the critical step.As soon as the roots are 20 to 40mm long. Long water roots are brittle, break on potting, and are poorly adapted to compost. Early transfer has a far higher success rate than waiting for an impressive root system.
8. Pot into a light open mix and keep it very damp.Multipurpose with a third perlite, kept wetter than you normally would for the first two weeks so the water roots are not shocked, then gradually normal watering.
9. Cover it for the first week or two.A clear bag held clear of the leaves reduces water loss while the plant builds its soil root system. Take it off gradually.
10. Expect a check, and do not panic.Some leaf yellowing or a droop in the first week is normal as the plant switches root types. Steady, damp, bright and undisturbed is what it needs.

Tips

• Willow stems steeped in water release compounds that help other cuttings root, which is why willow water has a long folk history. It is a mild effect, not a substitute for good technique.
• Herbs from a supermarket pot — mint, basil, and often coriander — root in water on a kitchen windowsill and turn one pot into a permanent supply.
• If you want reliability rather than the pleasure of watching, gritty compost under a cover beats water for almost every plant.

Common mistakes

• Waiting for a big root system before potting — The longer the water roots grow, the harder the transition. Roots at 20 to 40mm transfer far better than roots at 100mm.
• Leaving leaves under the water — They rot within days and the rot travels up the stem. Strip everything below the waterline.
• Topping the jar up rather than changing the water — Stale water is low in oxygen and full of bacteria. Change it every couple of days.
• Potting into ordinary compost and then watering normally — Water roots dry out very easily. Keep it noticeably damper than usual for the first fortnight.

If it doesn't work

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