I played charades the other night and had to enact the word “hormone.” You can imagine the pandemonium that ensued as I tried to elicit the proper response. Contrary to what you might be thinking, hormones have nothing to do with ladies of the evening or moaning.

Rooting hormones

Rooting hormones are available at many home improvement stores and garden centers.

Photo Credit: Lane Greer

Cuttings with rooting hormones

Dip the basal end of the cutting into your rooting hormone and shake off the excess.

Photo Credit: Lane Greer

Most of us know that hormones help regulate our bodies, but few people realize that plants also possess hormones. One of these, called auxin, is important when you’re trying to root cuttings. Commercially available rooting hormones are natural or synthetic versions of auxin at different concentrations. Generally, low concentrations are used for herbaceous cuttings (annuals and perennials), and high concentrations are used for woody cuttings (trees and shrubs). Commercial hormones may also contain cytokinins (another plant hormone), fungicides and other chemicals.

When to use hormones

  • With cuttings that root slowly.
  • With most woodies (trees and shrubs).
  • If propagation conditions aren’t ideal. (An ideal situation would be a greenhouse with a misting system [yeah, right] and warming mats.)
  • To speed up rooting. Some species that root without hormones can benefit from hormone application, just by speeding up the process.

There are powder and liquid hormone forms. Powders are easier to use because they’re hard to overapply. Liquids are either alcohol- or water-based and are stronger than powders. This makes it easier to burn cuttings using liquid rooting hormones. If you don’t know which type is best for your cuttings, check the label or ask at your local garden center.

Here are the rooting hormone requirements of some common species:

Must have hormones Maybe could use hormones Nope – don’t do it
Dahlia (Dahlia) Pocket petunia (Callibrachoa) Coleus (Solenostemon or Coleus)
Hibiscus (Hibiscus) Fuchsia (Fuchsia) Impatiens (Impatiens)
Cape daisy (Osteospermum) Some salvias (Salvia) Petunia (Petunia)
Lobelia (Lobelia) Snapdragon (Antirrhinum) Moss rose (Portulaca)

How to Use Hormones

  1. Pour a little into a cup or dish, keeping in mind that a little goes a long way. Don’t pour anything back into the bottle because this can spread disease! Throw away the unused portion.
  2. Dip the base of the cutting into the powder or liquid. Then tap or shake the cutting to remove any excess.
  3. If cuttings are very dry and no powder stays on, dip the cuttings in water first. But be aware that this breaks down the hormone faster, and it may spread disease.
  4. Stick the cutting into your potting mix or other growing medium.

What you need to know

  • Applying too much rooting hormone can damage the cutting. Just as taking too much medicine doesn’t cure you any faster, overdosing on rooting hormone harms the cutting rather than helps it.
  • Don’t get rooting hormone on the foliage, since this causes misshapen leaves.

So the next time you visit your grandmother’s garden and say to yourself, “I’d love to take a cutting of that magnificent dahlia, but I’ve tried it before and it hasn’t worked,” think about trying again. And this time use a rooting hormone to get that beautiful new plant. (And the next time you play charades and have to enact the word “hormone,” just quit while you’re ahead.)