Mexican Bush Sage (Salvia leucantha) is one of my favorite plants to use as a designer. It is fast growing, drought tolerant, and a great hummingbird plant. Mexican Bush Sage is also easy to take care of. This Salvia only needs to be trimmed twice per year. Once in July, when you should trim everything above your kneecaps. I like to call this technique 'Tony Soprano'ing the plant'. Get it? Just whack everything off at the knees. If you trim your plant like this you will be rewarded with lots of blooms in the Fall.
The other time to prune Mexican Bush Sage is in December. By the end of the year, Mexican Bush Sage starts to look scraggily. So now you should trim the the entire plant down to the ground. By doing this, you remove the old plant stems and allow the sun to hit the base of the plant. This encourages new growth to burst forth. See the photos posted above. Also in December (or January) add 2 cups of Gro-Power Plus to the base of each plant and water it in. Do this and you will have gorgeous purple blossoms all Spring.