Garden Myth: Sterilizing Pruning Tools with Bleach


20151214EAMost gardeners know that it is important to disinfect pruning tools (pruning shears, saws, loppers, etc.) before moving on to another plant. And that, if you’re removing diseased branches, tools should likewise be sterilized between each cut as well. It is, in fact, very easy to transfer a disease from one plant to another or even from an infected part of a plant to a healthy part via contaminated tools.

However, contrary to popular belief, bleach is not the product of choice for sterilizing metal tools.

On the one hand, bleach is corrosive and will damage the tool. And the now damaged, pitted surface can become infested with microbes that your sterilization efforts will no longer reach. Also, bleach is a skin irritant and can also cause serious damage to the eyes. In addition, bleach can stain and ruin your clothes. Plus, if you attempt to clean the cutting surface with a cloth or a cotton ball dipped in bleach, it will quickly disintegrate under the bleach’s oxidizing effect… as will your gardening gloves. Finally, bleach is very phytotoxic and can damage the cells of the branch you’re pruning.

In other words, use bleach for washing clothes and possibly, well diluted, for sterilizing pots, but keep it away from both plants and gardening tools.

Better Than Bleach

20151214EBThere are commercial liquids specifically designed to disinfect pruning tools, but your home probably already contains reasonably good products for that purpose that will cost you much less.

For example, you can dip the tool in a small jar of rubbing alcohol (isopropyl alcohol) or wipe the blade with a cotton ball or cloth dipped in rubbing alcohol. Other readily available products that sterilize well without harming tools are Lysol, Pine-Sol and Listerine. Use the original formula, not one of the multitude of offshoot products of unconfirmed effectiveness.

Other Helpful Hints


Dry the blade before making another cut.

Note that it is better to let the blade dry before the next cut, or to wipe it dry with a cloth, because even the products mentioned above, although less phytotoxic than bleach, can damage otherwise healthy tissues on the next branch to be cut.

And to avoid transferring germs from one plant to the next, make sure that your tool is sharp, since a dull blade contains pitted edges in which microbes find refuge from your sterilizing treatments.

Also, never apply disinfectants (alcohol, Lysol, etc.) directly to the wound. In the past, it was believed that wiping a tree wound with a disinfectant helped prevent future fungal infections. Today we know that it kills plant cells… leaving the wound more susceptible to fungus! Mother Nature provides plant wounds with natural protections against this type of infestation. It’s best to let them do their job!