Bogey, I was sure I answered you last night...I don't know where the post went.

Have you checked your drainage by filling the planting hole with water and observing how long it takes to seep out? My old and out-of-print rhody bible recommends "Even with raised plantings, prepare the top 12 inches of native soil beneath the plantings with organic material to improve soil texture and drainage."

And I wanted to caution you about the mushroom compost...it's too high in ph for growing healthy rhododendrons. If your base soil isn't alkaline to begin with and you used it as only part of your soil amendments, hopefully it will be alright since you seem to be asking after the fact and not before you planted :)

Any mulching material that may pack down with watering should be kept at a depth of 2" or so; mulches that are more loose which allow air to reach the soil surface can be applied in thicker layers.

thanks for your post. The mushroom compost was just one of several amendments, I am not too worried about it. I did try and see if the holes would drain and they were very slow. I went and got more mulch and now have about 2 inches all around the plant.

You can probably improve drainage by digging new deep holes near the plantings to act as soil drains. You woud backfill with sand and top soil mixed in with some old soil.

You can improve pH with top dressings of sulfur. It works best if you pull back the mulch, spread some sulfur, and then respread the mulch. The amount of sulfur to use is specified at:

Here is a link that might be useful: Check the section on pH.

rhodyman - the concept of digging deep holes is an interesting one. However, I have learned from experience that digging anything "deep" in this soil requires back breaking work due to the number of rocks and the heavy clay.

Instead I was thinking of running a french drain along the front of the bed as the bed slopes down towards the low point of my property. I am going to have the sprinkler company install some spray heads to irrigate the bed and they will have their ditch witch here so I am hoping I can "convince" the workers to dig me a trench or two.

Sounds brilliant. I did something similar and had to run the gravel in the backfill all the way to the surface to make it drain properly.

I expect that I will have to also run the gravel all the way up to the top. I was going to line the trench with fabric, put the PVC pipe and gravel in then cover up the top with fabric and then top with mulch.