Willow is famously forgiving. Cut a whippy stem, push it into damp ground, and there is a fair chance it will simply grow. Rooting cuttings in water takes that same ease and makes it visible: you can watch the first white nubs appear along the bark and know, rather than guess, that something is happening. It is a good project for a windowsill in January, and a neat way to turn one branch into a dozen new plants.

Choosing a willow and a good moment to take cuttings

Not every willow roots at the same speed. The vigorous, water-loving sorts root within weeks almost every time: white willow (Salix alba), crack willow (Salix fragilis), osier (Salix viminalis) and purple willow (Salix purpurea) are all reliable. Goat willow (Salix caprea) and some of the ornamental weeping forms are fussier, so take more cuttings than you need and expect a lower strike rate.

Timing matters more than technique. Take hardwood cuttings from late autumn to late winter, while the tree is dormant and leafless. The stem is full of stored energy then and there are no leaves to lose water through. You can take willow cuttings in spring, but you will be working against evaporation. Avoid a hard frost day when the stems are frozen solid.

Taking hardwood cuttings

You need very little kit:

• Sharp secateurs or a craft knife
• A clean glass jar or a plastic bottle with the top cut off
• Rainwater, or tap water left to stand overnight
• A pencil-thick to thumb-thick stem of last year's growth — smooth and flexible, not old grey wood

Then work through this:

1. Choose healthy stems with buds running along them. Skip anything with canker, dieback or scale insects.
2. Cut each one to about 20–30 cm. Make the bottom cut just below a bud and the top cut just above one, so you can always tell which end is which. Cuttings planted upside down will sulk, and may root poorly or not at all.
3. Strip the buds and any side shoots from the lower half, leaving three or four buds at the top.
4. Optional, but it helps: nick the bark at the base with a shallow diagonal cut. Roots form most readily where tissue is wounded.
5. Keep them the right way up in a labelled bag if you are not rooting them straight away. In a cool shed they will hold for several weeks.

Rooting the cuttings in water

1. Stand the cuttings in the jar, base down, with only the bottom 3–5 cm sitting in water. Submerge much more than that and the bark softens and rots.
2. Four to six cuttings in a standard jam jar is plenty. Keep the buds clear of the water line.
3. Put the jar somewhere bright but out of direct sun and away from radiators. A cool porch or a north-facing windowsill suits them well.
4. Top up the level as it drops, and be patient.

Roots usually appear in ten days to four weeks. Some willows throw out a fringe of roots in a week. If nothing has happened after six weeks, the material was probably too old or too dry — start again with fresher stems.

Changing the water: the part most people get wrong

This is what separates rooted cuttings from a jar of smelly stems. Change the water every three to five days. Lift the cuttings out, rinse them under the tap, run a finger around the inside of the jar to remove the slippery film of algae and bacteria, then refill. If the water turns cloudy or starts to smell, change it at once.

Rainwater is ideal. Tap water is fine, though in hard water areas a film of limescale can build up on the stems; a rinse deals with it. Do not add sugar, plant food or anything else to the water. The cutting is living off its own stored reserves, and anything extra simply feeds the algae.

Potting on rooted slips

Wait until the roots are 3–5 cm long and there are several of them. Water roots are brittle and built for water rather than soil, so move the cuttings before the roots grow long and tangle together.

• Use a small pot — around 9 cm — of free-draining compost. Mix in perlite, horticultural grit or sharp sand so it drains freely.
• Make a hole with a pencil, lower the roots in without pushing, then firm the compost gently around them.
• Water once and let it drain. Keep the pots light, cool and frost-free for a week or two, out of strong sun.
• Water regularly, but never leave them standing in a saucer of water.
• Once they are growing away, harden them off outside over a week or two before planting out in autumn or the following spring.

Plant them at the same depth the cutting sat at in the pot, and water well through the first summer. If you would rather skip the pots, a nursery bed of moist, weed-free soil works too — just keep the hose handy.

Troubleshooting

• Bases turn soft and black: too much stem submerged, or the jar sat somewhere too warm. Trim the rot back to clean wood and start again.
• Water goes green: too much light. Change the water more often and move the jar out of direct sun.
• Leaves but no roots: the cutting is spending its reserves on top growth. Move it somewhere cooler and dimmer, then wait.
• Roots rot after potting: they were damaged or left too long, or the compost stayed soggy. Fresh compost and a smaller pot usually fix it.

Willow water, and a final word on where to plant

Willow stems contain natural rooting compounds, so a weak infusion of chopped willow in water makes a useful pick-me-up for other cuttings — roses, hydrangeas, anything slow to strike. Steep a handful of chopped stems for a few days and use it fresh within the week.

Then give some thought to the eventual size of the tree. Willow grows fast: a cutting rooted this winter can be head-height in two or three years. Its roots hunt for water, so keep well clear of drains, pipes, foundations and septic tanks, and plant in open ground where it has room. Finally, only take cuttings from land you own or have permission to cut on, and leave trees in hedgerows and nature reserves alone.

Photo: Jessica Lewis 🦋 thepaintedsquare / Pexels