Question
What are the effects of chlorine on plant growth?
This is for my daughters science project so I will need any information that you can give me.

Thank you.

Answer
Hi Charrie,

In high concentrations, chlorine is toxic to plants. For example many plants that are kept near indoor swimming pools, where the water is heavily chlorinated, suffer leaf discoloration and damage. However, the chlorine that is often added to municipal water supplies is not usually strong enough to cause damage to plants.

I have also read that when chlorine gas is released by accident from chemical plants or damaged railroad cars, nearby trees have died as a result.

Plants in the Dracaena and lily family are particularly vulnerable to chlorine damage. This includes, Dracaena 'warneckei,' Dracaena'Janet Craig,' and spider plant (Chlorophytum).

Your daughter may want to use several small spider plants for her experiment and water each with different concentrations of chlorine and record the results. It may take several weeks for the differences to show up.

One other piece of information: Chlorine tends to dissipate (evaporate) from water that is left standing in an open container for 24 hours.

Please let me know if any of this is unclear or if you have any additional questions.

Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

You can E-mail me directly at: [email protected]

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