|The slightly less stressed lilac|
Here is what I saw and the history that I got. The small lilac is about 1 1/2 feet tall and fully leafed out. The leaves were folding and had a dry appearance all over. I first inspected for any obvious pests and saw nothing. I asked how the shrub was planted. The hole had been dug about twice the diameter of the container and about 4 inches deeper than the container. Part of the backfill soil was a potting soil mix and I noted that soil was mounded over the top of the original container root ball. I stuck my finger, the on the fly moisture meter, into the soil around the plant and it was slightly moist. Considering our lack of rain it had obviously been watered. I then took a trowel and carefully excavated an area to the edge of the original root ball. As I suspected it was dry. I then told the neighbor that we were going to dig up the lilac and replant it. Of course the response was, “Won’t that hurt it?” and my response was, “not as much as not doing it”.
The plant was carefully dug up and the root ball stayed intact. It was fairly dry although there were some new root shoots forming on a small area on one side. The extra soil that had been added to the top was removed so that we were back to what was originally removed from the container at the first planting. I excavated the hole and mixed the backfill material which was part native soil and part potting soil. Then the depth was adjusted so that the top of the original container soil would be about even with the surrounding area. I firmed up this soil layer and placed the plant back into the hole and replaced the backfill but did not cover the top of the original container surface. We made a small berm around the planting hole and added water. I watched and could see small air bubbles come from the plant root ball; this was probably the first water that was actually getting into the root system since it had been planted 3 weeks ago.
Why did this happen? It was soil interface issues. The root ball was like a large air bubble and the water could not penetrate it because it was capped off. It would be like trying to pour water into an inverted glass in a bucket, the water just goes down the sides but it will not fill up the glass. Now that the root ball had been uncovered and the soils on the sides mixed and firmed up a bit, the water can actually penetrate the root ball and not just channel around it.
Here is a link to a CSU tree planting guide that would apply to container grown shrubs as well, http://www.ext.colostate.edu/mg/Gardennotes/636.html
So the take away her is to always leave an escape route for air so that the water can get into the root ball. I checked back the next day and already the little lilac is looking a bit better.