Please help with non-blooming Clethra; prune? move? water?

We have a bunch of Clethra 'Pink Spires' that had been planted behind our house. All but 2 are under the second floor deck. The picture below is what some of them looked like when we moved in August 2007 (before I pulled out the dead one :P). I didn't know yet what they are so didn't realize that they probably should've been blooming. Last summer, the buds were all dried and shriveled, not one of them bloomed. I thought maybe too dry, but the downspout is back there and we have heavy clay, so it's usually pretty damp. Maybe too damp? From my digging around, there was nothing done with the soil before anything was planted (dig a pot size hole in the clay, stick plant in hole). One thing I'm going to do is pull a few out (maybe move, maybe not) because they're planted really close together under there, so I can get some amendments into the soil then.
Anyone know how to make these shrubbies happy?

Edited to add-they've grown well otherwise, and the leaves looked fine last summer.

This message was edited Mar 8, 2009 9:55 PM

Too dark from that overhang?

Resin

I was thinking that, but the 2 that aren't under the deck did the same thing last summer. Maybe they just aren't putting out roots b/c of the way they were (not) planted by the "landscapers" so they're not getting enough water? Or maybe it just got too hot.

Too hot in the summer, too cold in the winter, clay all year 'round...

I don't have that cultivar but I four other cultivars. I'm in 5b with clay soil. I amended our soil heavily with humus and added sulfur to make it a bit more acidic. All of mine are in at least part shade and most bloomed for me the first year. Even as tiny plants they still bloomed.

They are adaptable plants but I didn't think they'd like our clay. Maybe their roots are still in the original root ball because of the clay. I'm just guessing. I'd dig them up and amend the soil in a hole much larger than the root ball to try to get it to spread out.

Just wondering...even with the downspout in there, is the water soaking into the clay or does it tend to run off? In some of my unamended soil water tends to run off rather than soak in.

Another thought - try a pH test on the soil around the plants. Clethra does like acidic soils, and close to houses, it is often alkaline from builder's rubble dumped during construction.

Resin

Those are good thoughts. My next step is to test the soil all over anyway b/c I want to grow some plants that like acid, and I'll be testing around these guys too. All of my little planting areas need amending. The water does seem to stay around under there but tends to puddle so it's probably not getting to them, they like a lot of water, right? Do they get pruned now or in the fall? I'll need to cut them back before digging them up.

Unfortunately, it looks like most of these are in bad shape. I peeked at them while it was nice out yesterday and it looks like they heaved up during winter. The tops of the root balls are above ground level, and you can see where they dug out in the clay (big time bathtub effect). The ones not actually under the deck look ok. So probably the crappy planting job that kept them from blooming.