If you drain your pool into your landscape, yes, you will harm your trees and plants. Chlorine and other chemicals can damage and even kill trees. Chlorinated pool water in the soil forms chloride compounds, which a tree takes up by the roots. As this compound is spread throughout the tree, the leaves will begin to look burned and will dry out. Some leaves may turn yellow or drop to the ground early. To prevent this, follow these tips: Stop chlorinating your pool at least a week before you drain it Test the water to ensure the pH is between 7 and 8  Drain the pool slowly (this allows water to absorb into the soil over time) Consider non-chlorinated pool water as greywater rather than clean water. Test the water on a few replaceable plants before watering trees Scoop buckets of pool water to leave in the sun until no chlorine remains. Then use the buckets to water plants in other parts of your landscape. If your trees show damage from chlorine, irrigate the area with clean water (like from your garden hose) to flush out the chemicals and dilute the chlorine.