Hydrangea serrata ‘Kiyosumi’
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.
Hydrangea quercifolia ‘Snowflake’
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.
Hydrangea macrophylla ‘Zebra’
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?
There are many good Viburnum selections on the market, but this cultivar of Double File Viburnum gets high marks from us. It is laden with white lacecap blossoms in early June, like all the rest, but this particular form continues to produce blossoms on new growth all summer into fall. It is especially striking in autumn, when the white blossoms are set off by foliage that takes on wine tones.
Early info about the size of this plant reaching only 4-6′ was inaccurate. In our garden our specimen quickly reached 8′ tall, and as much in width. We’ve pruned our ‘Summer Snowflake’ to have a single leader with a more open habit. Plant ‘Summer Snowflake’ in good well drained soil where it will receive 6-8 jours of sun. Birds love take cover in it’s branches. Deer find them unappealing for the most part.
It’s time to love pink, and how can anyone say no to a flowering shrub that produces upright racemes of soft pink pea blossoms from late spring right through fall. Indigofera amblyantha, commonly known as Chinese Indigo, is a member of the legume family, so it fixes its own nitrogen from the soil and thus is a candidate for poor soil conditions. It asks for full sun and good drainage, and is hardy in zones 6-9. It wants to be a multi branched shrub but we have seen it charmingly pruned to a single leader (to appear as a small tree). In zones with severe winters, Indigofera amblyantha may get winter die back, so we suggest that if you try this pruning treatment, do so on plants located in a sheltered spot and consider it as an experiment. Then again, should die back occur, you can always enjoy this plant as the bushier shrub it is more inclined to be.
Attractive companion plants for Indigofera amblyantha are Calamintha nepetoides, Euphorbia ‘Blue Haze’ and Sedum ‘Maestro’.
Hayes Starburst Hydrangea is a floral arranger’s dream. This chance discovery, by Hayes Jackson of Anniston, Alabama, differs from the species by its showy display of clustered greenish white, multi sepaled star shaped flowers. It is a form of Hydrangea arborescens, also known as Smooth Hydrangea or Hills of Snow, and although native to the southeastern U.S., is cold hardy into zone 4.
Hydrangea arborescens ‘Hayes Starburst’ blooms on new wood, so there is little danger of winter damage to flower buds. We recommend cutting back the woody stems to 12″ in early spring to keep the plants tidy. Hydrangea arborescens prefers to grow in full to half day sun and in a well drained soil that still gets adequate moisture. If there is a common complaint about this species it would be that the flower clusters are so heavy that they weigh down the supporting stems. Some consider this an addition to the plant’s charm, and if it is sited on a slope or above a retaining wall, you could take advantage of its cascading habit. If an upright habit is preferred, situate a large tomato cage over the cut back stalks in spring, which will lend support. The height and spread of this shrub can remain a manageable 3′ x 3′, if pruned annually.