The next time you come up dry due to watering restrictions, consider using dishwater to keep your flowers and veggies from dying of thirst. The detergent residue in the water won’t hurt them; as you might recall, dish soap is often used as a base for natural pesticides, because it helps the mixture stick to the plants, isn’t toxic, and can be easily washed off later. Just make sure your dish soap does not contain boron or bleach. You can read more in the article below about boron compounds and chlorine and how they can hurt plants.
Now, one caveat here: dishwater is classified as a type of “greywater,” because it tends to be cloudy rather than clear. While it’s not considered sewage as such, in some areas, you’re required by law to dispose of greywater through a proper sewer system. Therefore, it’s a good idea to check your local regulations before dousing the daisies with dishwater.
Also, keep in mind that while dishwater is fine to use on your plants, not all greywater is created equal. If you’ve used water to wash poultry parts, for example, don’t use it to water anything you’ll later be eating, because of the risk of bacterial contamination. Bathwater, of course, is right out.
Want to learn more about using greywater to water your plants?
Check out these helpful resources:
Using Household Waste Water on Plants from University of California’s Cooperative Extension
UC Marin Master Gardener: Drought Prompts More People to Consider Using Graywater in Gardens
Irrigating the Home Garden from Virginia Cooperative Extension