This is the third willow acacia we are trying to grow in the same spot. The first one didn't make it; we think the second one froze (but it's possible that the spot is bad); and this is the third attempt. It's been planted about a month. It's been leaning over to the side and has not straightened out since planting. The black bark started appearing this week. It is in a spot that gets a lot of direct sun. We have a willow acacia about 30 feet away from it that has thrived - with no water.

Any ideas what is causing the black bark? What can we do to help it take and thrive?