A general rule for Texas sage pruning is to wait until after the plants have bloomed. Leucophyllums bloom throughout the warm months so the best time to prune is in very early spring.
Synonyms: Texas ranger, cenizo, silverleaf.
You can remove as much as one-third of the foliage at this time without causing too much stress to the plants.
Avoid hard pruning (removing more than one-third of the top growth at one time) as plants may not recover well.
From spring through fall the Texas sage bush will bloom intermittently with splashes of color--some types are even fragrant.
If you prune during this period you will be removing the bud wood from which the blooms will be produced.
It is best not to shear Texas ranger. Instead use hand pruners to head back branches that have grown too tall and to remove broken or crossing wood. This type of pruning will result in a more natural looking bush and will remove less flowering wood.
If you like to shear plants into topiary shapes, this is probably not the best plant to use.
It will need constant trimming to keep it neat. It's easiest to let it assume its natural billowing growth habit.
If you "inherit" a Texas sage plant that has been trimmed into a neat little ball, you can rescue it--and yourself--from this fate by staggering the length of the shoots with hand pruners. This will take at least a full growing season to rectify and the bush will look a little funny during the transition. In the end, it will be worth it as you'll have a more natural, lower maintenance shrub.
If you don't have the patience for this, you could cut it to the ground and allow it to grow back into its natural form. The risk with this Texas sage pruning method is that it might stress the plant too much. You could lose it.
The main thing is to keep the plants dry. Leucophyllum frutescens doesn't like moist soil--especially in the winter. Overwatering will also encourage excess growth which will cause you to have to prune the bushes more often.
The other thing Texas sage bushes resent is shade. They grow and bloom most abundantly in full sun. Its tolerance of drought, extreme temperatures and wind make it a great desert plant.
Plant it in USDA zones 3-10.