One way that walls talk to us is through the accumulation of biological growth on surfaces of buildings. Moss, vines, grass, trees, mildew, and mold are all-natural organisms. However, they are not supposed to live on or in your walls.
If there is sustained biological growth (of any kind), the wall is telling you that it’s holding moisture, which is sustaining this growth.
The moisture’s presence can be from a myriad of sources, and the bottom line is that moisture can cause deterioration – especially when combined with freeze-thaw cycles. If you have biological growth on your building, you should know this is an indicator that something is going on within your wall. It could be an overflowing gutter, an open void or crack, displacement, or other sources of moisture intrusion requiring further evaluation. 
There are numerous steps to take in order to rid the surface of these contaminants. First, it might take cleaning or physical removal. Then, you must kill any growing or living contaminates. If the actual spore or root system is not killed, then removal may only be temporary. Lastly, once you remove the biological growth, you need to make sure that you have eliminated the source of the moisture presence so that it does not return.
If your wall is telling you something, please contact Trisco Construction Services at 419-339-9912 for an evaluation.