Less-experienced contractors, when first selecting a cleaner to use, often ask me if it will kill the grass. It is important to state right at the top that any cleaner strong enough to work the way we want it to IS strong enough to harm both plants and animals - even those "green" cleaners.
Most experienced contractors never have this problem. They have learned through experience what they can and cannot do.
Basically, a contractor who frequently works near landscaping plants has to understand the nature of plants and soil.
Dry soil absorbs any moisture within moments, soaking it in as far down as it will go. If you then realize that all plants live by drawing moisture from the soil, you see the recipe for disaster.
When the soil is dry, the plant waits for the first sign of moisture and starts to immediately suck it in. If that first drink is some highly caustic or acidic cleaner, the plant can be drinking a lethal mix.
Experienced contractors pre-wet the soil, soaking it with enough water that the soil cannot absorb anything else. In that case, the cleaner that lands on the soil merely sits on top of the soil ? away from the roots ? and just evaporates in the sun.
Within a few days, it is completely broken down and harmless.
So, by pre-soaking the soil you can use industrial strength cleaners and even bleach on house siding or other surfaces tangent to landscaping and never harm the plant roots.
Pre-soaking the lawn edges allows you to use the strongest concrete cleaner on a driveway without any concern about the grass on the border.
The blades of the grass (or leaves of the plant) can be a different story, though. Leaves can be burned by strong chemicals, just like your skin can be burned.
Pre-wetting the leaves (which of course occurs when you are pre-soaking the soil) minimizes this danger, since any cleaner that might land on the leaves would be diluted by the rinse water already there. Rinsing plant areas off immediately after completing any wash job insures that any cleaner residue is rinsed off or well diluted.
So, water is the best protection the plants have against even the strongest cleaners we use. All it takes is a little planning and effort to avoid huge headaches later on.