Yesterday I was talking to my neighbor, and he was telling me he was cleaning the trim on his house with Dawn (dishwashing detergent used in the US) mixed in water. I thought I read somewhere that Dawn can damage or kill plants. Is this true? I was thinking about trying this myself, but have shrubs and flowers under the trim I want to clean.
I've used sudsy dish soap such as Dawn before to combat insects such as aphids and it is quite effective and the one I used (it wasn't Dawn specifically) was biodegradable and that's important to me.
The key to using Dawn or anything (siding cleaner, bleach, etc.) around plants is that you need to lower the concentration of the chemical low enough that it doesn't harm the plants. A number of years ago I cleaned my siding with a soapy liquid something like Dawn with bleach in it. In preparation for this I thoroughly soaked the vegetation with water - I DRENCHED it to be sure - and then cleaned the siding as prescribed by the cleaner, then I hosed all my plants down again, ensuring that any of the cleaner was highly diluted.
Plants are pretty resilient and tend to fare well under some extreme conditions. A little insurance in the form of a good hosing down before/after the cleaning should be all they need.
I have been using detergents like Dawn dish soap to wash my vehicles and even went as far as using bleach water to clean the siding of my home right next to a big hedge bush. So far I haven't seen any ill effects from doing so. Of course I do use things in moderation, a little Dawn as well a little bleach goes a long way in a bucket of water, but I guess if it bothers you then maybe a bottle of "Simple Green" would be a great thing to keep around the house.
YES!!! Unfortunately it has taken me nearly killing two hibiscus plants to figure it out. I used Dawn diluted in a small spray bottle when I noticed aphids on my first plant. Within a couple of days all the leaves began to yellow and die off. I did not make the connection, however, until several weeks later I noticed aphids on the other plant and repeated the procedure. Of course within two days all those leaves began to yellow and fall off. I used approx. 2 Tbsp. dawn with an 8 oz spray bottle.