The Kitchen-Cupboard Rooting Test: Five Tonics, Three Cuttings, One Windowsill

A question that keeps coming back every autumn

Type 'willow water' into any UK gardening forum in October and you'll get three answers before anyone has finished their tea: that it's magic, that it's nonsense, and that honey is better anyway. The cinnamon crowd arrive shortly after. Since I had a spare windowsill, a propagator lid doing nothing and a tray of modules, I decided to run the comparison myself this autumn — 2026, for the record — with three cuttings that British gardeners actually bother with: lavender, rosemary and pelargonium.

This was not a replicated trial. It was a three-per-treatment, one-run, kitchen-table sort of investigation, and I'll flag that repeatedly, because the internet has a habit of turning one person's tray of sticks into a law of nature. Treat what follows as a signpost, not a verdict.

The five contenders

• Tap water soak — the control, and the one everyone forgets to include.
• Willow water — fresh Salix shoots steeped in water, on the theory that willow is stuffed with rooting-friendly compounds.
• Honey — a roughly 1:10 honey-and-water soak, borrowed from the world of cut-flower care.
• Cinnamon — ground cinnamon dusted on the cut end, favoured by the houseplant crowd for its antifungal reputation.
• Commercial rooting powder — the standard garden-centre product, containing a synthetic auxin (usually IBA) with a carrier and, in some formulations, a fungicide.

What the plant science actually says

Rooting is a hormonal event. Auxins — chiefly indole-3-acetic acid inside the plant itself — accumulate at the base of a cutting and prompt cells there to dedifferentiate into root initials. Commercial powders work because IBA and NAA are stable, measurable and formulated to linger at the wound. That isn't a conspiracy; it's chemistry with a batch number.

Willow's reputation rests on thinner evidence. Willow bark and young shoots contain salicylic acid and a range of phenolic compounds, and there are decades of folk reports of willow extract improving rooting in other species. Salicylic acid is bound up with plant defence and can influence rooting, but the amounts in a jar of home-brewed willow water are wildly unpredictable, and the often-repeated claim that willow water is loaded with IBA is not well supported in the horticultural literature. Its more defensible benefit is antimicrobial: a cleaner wound rots less.

Honey is hygroscopic and mildly antimicrobial, which explains its use on cuttings — but sugar water is also a lovely medium for mould. Cinnamon's cinnamaldehyde is genuinely antifungal in lab conditions; whether a dusting on a cutting helps, does nothing, or slightly burns the tissue at high doses is much less clear.

The protocol, so you can pick it apart

1. Timing: late August to mid-September 2026, while stems were semi-ripe and the light was still decent.
2. Material: Lavandula angustifolia 'Hidcote', Salvia rosmarinus 'Miss Jessopp's Upright' (still sold as rosemary in most catalogues), and a scented-leaf pelargonium.
3. Cuttings: lavender and rosemary at 8–10cm, trimmed just below a node with the lower leaves stripped; pelargonium as a 7cm tip cutting with flower buds removed.
4. Media: 50:50 peat-free multipurpose compost and perlite, in modules, watered and left to drain properly.
5. Treatments: 15-minute soaks for water, willow water and honey; a light dusting for cinnamon and powder. Three cuttings per treatment per species — 45 cells in all.
6. Conditions: a lidded windowsill propagator, south-facing, no bottom heat, vents opened daily for ten minutes to swap the air.
7. Assessment: pelargonium checked at four weeks, the two woody subjects at eight. Root score: 0 for rot or nothing, 1 for callus only, 2 for one or two short roots, 3 for a proper little rootball.

What came out of it

Treatment	Lavender	Rosemary	Pelargonium
Water (control)	1.0	1.0	1.7
Willow water	1.7	2.0	2.3
Honey	1.3	1.3	1.0 (two rotted)
Cinnamon	1.0	1.3	1.7
Rooting powder	2.3	2.3	2.7

Scores are the mean of three. Powder won on every species, which will surprise nobody who has read the label. Willow water was a clear second and, interestingly, produced the cleanest wounds — no fuzz, no blackened ends. Honey underperformed and did for two pelargonium cuttings, both of which went soft within a fortnight. Cinnamon came out close to indistinguishable from plain water, though those cells showed noticeably less surface mould than the control.

Reading these numbers honestly

Three cuttings per treatment can't separate a real effect from luck. The pelargonium result is muddied further because pelargoniums root almost regardless of what you do to them, which makes them a poor test subject and a very good confidence trick. Lavender is the honest one: slow, sulky, and quick to punish a wet compost mix.

The most useful finding was about hygiene rather than hormones. Everything that rotted did so at the base, inside a sealed propagator, in compost that stayed wet. Willow water's apparent advantage may owe more to its antimicrobial phenolics than to any auxin it does or doesn't contain — which is a less romantic conclusion than the folklore, but a more useful one.

Run your own version

You need nine cells minimum: three species, three treatments. Keep one as a water control — without it you're just collecting anecdotes. Label everything, use a fresh blade, and resist the urge to tug at the cuttings to see how they're doing. If you want a stronger test next autumn, run two trays side by side and swap which one gets the sunnier end of the windowsill halfway through, so position doesn't quietly do the work for you.

Rooting aids are a nudge, not a switch. Light, temperature, hygiene and the condition of the parent plant do most of the heavy lifting. The powder simply makes the nudge measurable — and this autumn, on this windowsill, measurable beat mystical.