Well, the Clethra alnifolia ‘Caleb’ (‘Vanilla Spice’) made it through this past winter with almost no ill effects–other than one small dead branch–in spite of having 22″ of snow dumped on it during our blizzard. As you can see from the photo at right (click on the photo for a better view), the plant has clean, healthy foliage and will have plenty of blooms in a few weeks. The shrub has only put on 3″ of new upward growth this year, compared with 9″ last year, although the side branches are filling out nicely. Also, the branches farthest from the light are leaning slightly toward the sun (phototropism), so I suspect the plant would be happier in light shade or filtered sun instead of medium shade; and it’s definitely not a candidate for heavy shade. The remaining question is whether the plant height will remain short or whether it will continue to grow. I’ve made sure the plant receives plenty of water during the dry spells, and I applied a 5-2-3 fertilizer early in the season since I don’t want to over-fertilize a young plant. The Clethra also has excellent soil and drainage.
I will be disappointed if the plant ends up being under 3’—for purposes of what I need in my own garden—but, if it does end up being a dwarf, it will still make an excellent recommendation for short hedges or an addition to mixed borders.