Does Powder Rooting Hormone Expire?

History of Synthetic Compounds

• One plant contains a large quantity of the auxin hormone, and is used to make a liquid rooting compound. If you soak willow (Salix babylonica) branches in water, the liquid solution can be used to stimulate root growth in plant cuttings. Willow grows in U.S. Department of Agriculture plant hardiness zones 6 through 8. The problem is that the results of the willow water are not always predictable. A synthetic powder was developed in the 1930's to give reliable results every time. Various manufacturers introduced a number of powder products that boasted guaranteed results when rooting plant cuttings. Each of the products deteriorates over time.

Rooting Hormone Ingredients

• Every manufacturer has a formula for the powder rooting hormone they produce. The active ingredient in most of the compounds on the market is indole-3-butyric acid, known as IBA or naphthaleneacetamide. The strength of the chemical in the powder varies by manufacturer. Other ingredients in the powder may include methyl naphthaleneacetic acid, tetramethyl thiuramdisulfide, thiram and talc. As with any chemical formula, the composition eventually breaks down over time.

Shelf Life

• The shelf life of a powder rooting hormone is three to four years. As the hormone powder ages, the effectiveness of the auxin declines. The product deteriorates more quickly when exposed to excessive temperature changes and sunlight. For the home gardener, a bottle of powder rooting hormone may last much longer than the recommended shelf life. Consider replacing your hormone powder every few years to keep your propagation success rate high. Your cuttings will root more rapidly and produce healthier roots with fresh hormone powder.

How To Use

• Extract a small amount of the rooting hormone onto a sterile disposable container. Your plant cutting should be about 3 to 4 inches long. The basal end of the stem cutting must be bare. Strip the leaves by sliding the stem firmly between your thumb and index finger. Dip the basal end of the stem into the powder rooting hormone of your choice to apply a thin coat of the powder. Tap or shake the stem gently to remove excess powder. Stick your cutting into the growing medium. Discard the disposable tray and extra hormone. Do not pour the powder back into the original container, so there is no risk of contaminating the rest of your rooting powder.