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Rooting Hormones

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Root hormones
Photo Credit: Lane Greer
Rooting hormones are available at many home improvement stores and garden centers.
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.

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 hormonesMaybe 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)
Warnings
  • It’s more difficult to root plants in winter because light levels are low and it’s more difficult to keep the rooting media warm (around 70 degrees F for most species).
Tips
  • Other plants that benefit from hormone application are heliotrope, mandevilla and bougainvillea.
Tools
  • Some common rooting hormones are Rootone® (a powder) and Dip ’N Grow® (a liquid).
Facts
  • Auxins are produced in the tips of plants, called the apical meristem. Cytokinins are produced in plant roots.
 
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