I planted two hydrangea kardinal in my zone 5a garden--sun much of the day. The following summer one shrub produced two large gorgeous flowers, purple to blue to red, and the other none. This summer the shrub produced no flowers, but the other one (flowerless last year) gave one beautiful flower that's lasted for a month. Both shrubs seem healthy. Any suggestions on how to get greater flower production, or will Nature see to it in her own sweet time?
hydrangea kardinal
For starters, if the plants are still small you can't necessarily expect a ton of flowers until they get bigger. But the fact that the one that bloomed last year didn't bloom this year leads me to suspect one of two things. First thought is did you do any pruning--most H. macrophylla cultivars bloom on old wood, so if you pruned too late in the year then you cut off the flower buds without realizing it (I'm not familiar with this cultivar, but I don't think it's one of the ones that blooms on new wood). If you didn't prune, then it could be your climate--the H. mac's that bloom on old wood are better off in zone 6 and up, in zone 5 if you get too much cold it can freeze the buds, resulting in no or few blooms. In your climate, you're better off with one of the reblooming/bloom on new wood cultivars such as Endless Summer, or a different species such as paniculata or arborescens which bloom on new wood and are more cold tolerant.
Thanks very much for the reply and the suggestions. I didn't prune (the plants are full size now I think). I think I'll try putting burlap protection over the plants this time and see what results I get. I love the Kardinal colors.