Retaining Wall It was more than ten years ago when I visited the greenhouse looking for plants for a newly created stone retaining wall.  The retaining wall was created to make room for a garage addition.  There was a lot of debate about what was being retained in that wall, it came with a two-foot diameter, mature, black walnut tree.  There were pros and cons, but the pros won out (later on we may have decided to go with the cons) and the search for compatible plants was on. If you aren’t aware, Black Walnut trees, put out a toxin called juglone that surrounds the tree preventing invading trees from taking hold.  There are a lot of plants that cannot survive in this toxic environment, so I wanted to make sure I didn’t waste my money on plants that would die.  The greenhouse manager suggested several plants including three variegated yuccas and we took them all home for planting. Yucca survival I like yucca plants, overtime they will mature and send up a tall flower spike that produces a ton of white flowers, very dramatic.  I looked forward to seeing that someday.  I watched the little yuccas over several years,