Harnett County, North Carolina
 
Cooperative Extension 
 
Will the chlorine from a swimming pool harm my plants?

ASK THE HORT AGENT

Question Will the chlorine from a swimming pool harm my plants?

Answer Chlorine is a lot like fire. We canít live without it, but it can harm you if improperly handled. Contrary to my thoughts in high school, chemistry is very important in our everyday lives. Understanding our environment is one of the keys to peace and harmony. So in pursuit of peace and harmony, prepare your mind for chemistry.

Chlorine (Cl2) does not occur naturally in nature. Chloride (Cl-) is the ionic form of chlorine which is found in nature. Chlorides make up much of the salt dissolved in the Earth's oceans. Approximately 1.9% of the mass of seawater is chloride ions.

Chloride occurs in the blood and tissues of all living organisms Ė plants and animals. It is also the most recent addition to the list of essential elements for plants. Although chloride is classified as a micronutrient, plants may take up as much chloride as they do other elements such as sulfur. Chloride, nitrate, sulfate, borate, and molybdate are all anions (negative ions) in their available forms. In that form, they are antagonistic toward each other. Therefore, an excess of one can decrease the availability of another. Too much of any nutrient can be bad.

Chlorine (Cl2) is a poisonous, green gas used to make bleaching agents and disinfectants. Commercial liquid chlorine (compressed chlorine gas) is used as a water treatment to kill bacteria in drinking water and swimming pools.

Both concentration and length of exposure are important in the degree of damage caused by chlorine. In other words, even exposure to a low concentration of chlorine for a long period of time can cause toxic effects. Likewise, exposure to high concentrations of chlorine for even short periods of time can cause severe toxic effects.

According to Clemson University, there should be no effect on nearby plants if pool water is splashed on them by normal sized cannon ballers. Larger plants (and animals) can tolerate the concentrations that are recommended for pool water.

If your pool has a high chlorine content and needs to be drained, uncover it and allow the chlorine to dissipate before using the water for irrigating the landscape. The chlorine can be chemically removed by adding sodium thiosulfate or sodium sulfite to the water.

Many municipalities and homeowners are switching from chlorine to alternatives like Ozone for water treatment. Alternatives often require redesigning which may not be feasible. For more info about chlorine visit http://www.clemson.edu/aiken/local/PDF/c_facts.pdf

If you donít have internet access, don't hesitate to call the Extension Office at 893-7533, write us at PO Box 1089, Lillington, NC 27546, or email me at gary_pierce@ncsu.edu

Chlorine is classed as a biocide, which means it will kill all life if applied in sufficient concentration. Yet most of us eat chloride everyday in the form of table salt (sodium chloride Ė NaCl). What a difference one ion makes.

Gary L. Pierce

Horticulture Extension Agent

Harnett County