Hydrangea selections:
Top Row (l-r): Hydrangea aspera 'Macrophylla', H. macrophylla 'Blaumeise', H. serrata 'Kiyosume'. Middle Row (l-r): H. macrophylla 'Mariesii Variegata', H. macrophylla 'Glowing Embers', H. quercifolia 'Little Honey'. Bottom Row (l-r): H. arborescens 'Annabelle', H. macrophylla 'Enziandon', H. paniculata 'Tardiva'.
In the Pacific Northwest, few shrubs can surpass hydrangeas for variety and summer color in the garden. Whether you're a budding gardener or an ardent collector, you can never seem to have enough of these beauties in your garden. Hydrangea flowers range in form from subtle, understated lacecaps to the largest mopheads so cherished in floral arrangements. Other varieties may climb or offer variegated or golden foliage as well. This truly amazing group of plants is only beginning to be appreciated and fully utilized in our gardens as new species and varieties are made available to the gardening public.
These plants love our maritime climate with relatively mild winters and cool summers. Our generous annual rainfall is most advantageous too although care must be taken to be sure that they are watered deeply during the summer.
It is generally best to plant hydrangeas in areas that do not receive afternoon sun, with the exception of H. paniculata cultivars. Hydrangeas prefer moist,well-drained soils that have been amended with plenty of organic matter and they benefit from regular watering during the summer months. Other than an occasional slug or two feeding on young leaves, all hydrangeas are generally pest-free.
Hydrangea macrophylla, H. serrata and H.quercifolia are best pruned lightly in early spring just as the buds swell on the stems. With selections of these species remove weak or spindly stems and lightly thin older stems that have started to branch (the weight of additional flowers on these branched stems will cause the plant to flop badly). As a general rule, it is helpful to try to make sure to leave at least four pairs of buds on the stems that you are keeping to ensure blooms. H. paniculata and H. arborescens bloom on the current season's growth and should be pruned back hard in February-March. H. aspera varieties should be pruned hard for their first three years at the cost of not blooming to promote a fuller, more attractive plant later. Climbers such as H. anomala petiolaris and Schizophragma hydrangeoides 'Moonlight' do not require pruning.
As a general rule, organic matter or additives like Aluminum Sulfate will make the soil more acidic (lower pH) and tend to turn most hydrangeas blue (except for white-flowering forms). Garden lime or the additive Potassium Nitrate will make soil more alkaline (raise pH) and tend to turn hydrangeas pink. Certain varieties may have a limited range of color due to breeding (ie. H. 'Glowing Embers' can be purple in acidic soil but never blue).
I hope that this clears up some of the confusion regarding these remarkable plants and that you might be inspired to try a few new varieties in your own garden. Happy gardening.
Cheers, Tim
