Do I actually need rooting hormone?

Rooting powders and gels contain a synthetic version of auxin, the hormone a plant already produces at leaf joints to initiate roots. Supplying extra tips the balance in favour of root formation. The size of that effect depends almost entirely on how readily the plant roots anyway.

Safety

Step by step

1. Skip it for easy subjects.Pelargonium, fuchsia, penstemon, salvia, mint, coleus, willow and most soft-stemmed plants root readily without it. The hormone adds nothing measurable and is one more thing to buy.
2. Use it for woody and semi-ripe cuttings.Shrubs, evergreens, hollies, box, hydrangea, and hardwood cuttings taken in winter. Here it improves the strike rate noticeably and often speeds it up.
3. Choose the right form.Powder is the traditional option and keeps well if it is kept dry and dark. Gel coats the cut surface more evenly and does not shake off. Liquid concentrates are used by nurseries and are usually more than a garden needs.
4. Decant a little rather than dipping into the tub.Tip a small amount into a lid or a saucer, dip into that, and throw away what is left. Dipping cuttings straight into the container contaminates the whole tub with plant material and fungal spores.
5. Moisten the cut end first.A quick dip in water so the powder adheres. With gel this is unnecessary.
6. Tap off the excess.You want a light dusting on the bottom few millimetres, not a clogged lump. Too much genuinely inhibits root formation — this is the one place where more is worse rather than merely wasteful.
7. Apply to the very base and the lowest node only.That is where roots form. Coating the whole stem does nothing useful.
8. Do not treat it as a fix for bad technique.Hormone will not save a cutting that dries out, sits in soggy compost, or was cut in the middle of a stem. Preparation, humidity and a gritty mix matter far more.
9. Replace it every couple of years.The active ingredient degrades with light, heat and damp. An old tub found at the back of a shed is probably doing nothing.
10. Consider the honest alternatives.Willow water — willow stems steeped in water for a day or two — has a mild genuine effect. Honey and cinnamon are sometimes suggested as antifungals rather than rooting agents and have very little evidence behind them for either purpose.

Tips

• Keep the tub dry, cool and dark, and decant what you need. That doubles its useful life.
• The best free rooting aid is taking the cutting at a node, in the morning, from a non-flowering shoot.
• If a plant will not root with hormone, try a different type of cutting or a different season rather than more hormone.

Common mistakes

• Using a heavy coating in the belief it will help — Excess auxin suppresses root initiation. A light dusting on the base is the correct dose and the label rate is not a minimum.
• Dipping cuttings into the main tub — It contaminates the product with sap and fungal spores, and one diseased cutting can spoil the lot.
• Relying on hormone to compensate for wilting or wet compost — Neither problem is a hormone problem. Humidity and drainage are what decide most cuttings.

Questions people ask