As I drive into the neighborhood to find the home which I will be inspecting, I examine homes to see general trends. I was immediately struck by the landscaping around the homes. About half of the houses had eunonymous or hawthorne bushes close to the structures, so I guessed that there may be a problem.
As I pulled in front of the home, I spotted the heads for the sprinkler system, and I knew what I would find: damage to exterior trim and walls. How could I be so sure, when I had not stepped out of the car yet? Because I knew how the plants would grow, how the watering system would be set up, and what situation this would cause. I also knew that the pest control firm coming to produce the WDI (wood destroying insect) report would say, since I was going to say the same thing for a different reason.
You could almost say that homes need to breathe, but it would be more accurate to write that air flow is needed to prevent problems. Bushes keep air from flowing around the building, which helps moisture stay on the surfaces where it could help deteriorate that surface. This environment also encourages termites, who love to hide and love moisture. Sprinkler systems will have their water kept at the wall when blocked by the plant.
Plants should be positioned where a foot space between the leaf line of the plant and wall can be easily maintained. When you think about it, a foot is not that great of a distance. It makes a tight walking space. To help further reduce moisture on the walls, a drip irrigation system is far better than a sprinkler system. Drip irrigation places water on the ground where the roots are, so it cannot splash back against the wall and trim. Drip irrigation also saves water, since it prevents evaporation.
If you need to replant to better position your plants, wait until autumn. It is less stressful on the plant then. Minor pruning can be done throughout the year. If you do have plants against the walls, consider that damage will be more common on wood surfaces behind them, but brick and stucco can be damaged too. You have to make a consideration to improve air circulation in these areas.