The reason(s) amending of soils in small areas is counterproductive do not vary with the type of soil. Sandy, silty or clay-like, it makes no difference. You do not want to install plants in pockets, strips or zones of one soil texture surrounded by soil of a different texture, as this sets them up for likely problems with how water moves into and out of the soil around their roots. In the case of plants to be left in place for many years (or indefinitely) without lifting and re-planting there is no point in incorporating organic soil texture modification materials (bark, compost, peat...) even if the bed is large enough to minimize or eliminate water movement problems for most of the plants - once the amendments decompose the effects they produce will be lost. Inorganic amendments like perlite and sand do not decompose but enormous amounts of these have to be added to change a heavy soil into a light one. And if too much is added then a droughty and infertile (leaching) situation may be produced, that may be more limiting than a heavy clay-like soil. The most straightforward approach is to choose plants adapted to the existing soil type and plant these in wide, shallow holes dug out of that, loosening it over a wide area beforehand and mulching well afterward. The most satisfactory mulch for woody plants appears to be clean wood chips. If arborist wood chips available nearby tend to have bramble stem sections or other undesirable material mixed in then play chips from a local dealer may be the best bet. Ones we obtain here as cedar play chips are very nice but have become quite pricey, as far as it goes.

A bigger picture would help. Do you have a bigger one that you could put on a photohosting site like photobucket?

NO! Do not do a rejuvenation to any Viburnum!! Michael Dirr, who wrote the book on them and who has developed many of them, recommends infrequent and light pruning of Viburnums, if any at all. This is my favorite shrub. I have at least two dozen and about 8 different cultivars. I believe the one you have is a Burkwood, but it could also be Judd. Either way, it's gorgeous, pretty much pest- and maintence free, and you should definitely NOT coppice it. You do that to a Rose of Sharon or a lilac, but never to a Viburnum. Here is a link that might be useful: Michael Dirr's Viburnum for American Gardens

That's what it looked like to me. Larry