I am the activity director at a nursing home that specializes in psychiatric patients and we want to start a garden. The trouble is, alot of them urinate whenever and wherever the want, including the garden. I plan to keep most of the plant up high, but is there anything I could plant in the ground or planters that might resist the high concentrations of ammonia? Also, given my black thumb what are good, tenacious outdoor plants. We are located in San Antonio. Any help would be appreciated.