More subtle and nuanced than the big mop heads, the species H. serrata hails from the higher elevations of Japan and Korea and is considered more reliably cold hardy than most H. macrophylla. What caught my eye about this particular selection H. ‘Kiyosumi’ , even before the blossoms developed, was the attractive brick red tint to the new foliage. The 4-6″ lace caps are composed of tiny rose tinted fertile flowers, accented with a skirt of larger florets colored white to pale pink with a rim of brick red. This compact selection grows 4′ x 4′, and is hardy to -10F without stem dieback. H. serrata ‘Kiyosumi’ does bloom on old wood, and I can vouch that it survived the winter of 2014-15 quite admirably.
An old favorite for the shade garden is the double form of Oakleaf Hydrangea, H. ‘Snowflake’. The bold oak leaf shaped foliage is handsome all season, but in early summer it bears long (10-15″) panicles of exquisite double white to celadon green florets which age beautiful to shades of pale green and rusty rose. It’s grace and beauty never ceases to draw compliments.
Like all H. quercifolia, ‘Snowflake’ blooms on old wood, so care should be taken when pruning so you are not sacrificing too many potential blossoms. H. quercifolia ‘Snowflake’ grows 7-8′ tall and wide, but the weight of the blossoms gives it an arching habit. Although this particular form can be grown in full sun if it has evenly moist soil, it has always been happier in our cooler, shady border. It is hardy in zones 5-8.
I was recently alerted about the new Hydrangea macrophylla ‘Zebra’ from my gardening friend Barbara Smith, who suggested it as a great Hydrangea for cut flowers. (Didn’t need much convincing; I bought 3). This new patented selection is a sport of the all white cultivar H. ‘Schneeball’ (German for Snowball) and is distinguished not only for its 3.5-5″ trusses but for its very dark green foliage and almost black stems. I hear the flowers age to a wonderful pale green. Plants form compact shrubs 3-4′ tall and wide. I suspect that this form will only bloom on old wood, so I am trialing one in a protected area and the others in a more open spot in the garden. The literature says it is hardy to zone 5, but we’ll see if that means bud hardy, won’t we?