But a container plant only shares water with the roots in the container. That allows for control. An in ground plant here would be sharing the same amount of water with oak trees and assorted other vegetation. When the moisture is supplied with generous rainfall, it lasts for a while. When in ground plantings get supplemental water, the competition can be fierce since it's only covering a small area relative to all the other thirsty plants around it that aren't getting the extra. It doesn't last as long and sometimes other things get more benefit than the intended target. In a year or so, the competition becomes uneven. What might have started well may decline. With any kind of water rationing, the control weakens because you can't provide enough to account for the competition for the moisture. Probably never an issue in areas with consistent regular rainfall.
