Hydrangea arborescens, also known as smooth hydrangea, is one of our finer native shade plants. Growing to a height of approximately four feet tall and three feet wide, smooth hydrangea is an excellent plant that creates impact and drama in the shady border.
In addition to being beautiful, the native species, Hydrangea arborescens, is a larval host plant to an exciting woodland beauty, the inimitable Hydrangea Sphinx moth.
A popular cultivated variety of our native hydrangea is the ‘Annabelle’ hydrangea (Hydrangea arborescens ‘Annabelle’). Unlike the species form, which is a lacecap-type hydrangea and generally available only from specialist native plant growers, ‘Annabelle’ has the classic puffball or “mophead” look and is easily found at garden centers. That’s Annabelle in the photo on the right.
With billowy white blooms reminiscent of fluffy meringue or big scoops of vanilla ice cream, ‘Annabelle’ is a superb addition to any garden. ‘Annabelle’ hydrangeas bloom in early summer, usually in June, and boast baseball-size flowers that will light up the gloomiest areas of the shade garden. Even after blooming, the flowers remain attractive for a long period of time while they fade to a soft tan and then become translucent as if they were made of crepe paper.
If you prefer a more subtle beauty, then give Hydrangea arborescens ‘White Dome’ a try. This cultivated variety has the lace-cap type blooms. Although the flowers are not as large as Annabelle, they are still elegant. The pristine white lacy flowers capture the light and seem to glow in the shade. I have both ‘Annabelle’ and ‘White Dome’ planted in different areas of my woodland garden and I cannot honestly say that I prefer one over the other. They are both outstanding in their own right. So if you have the room, I recommend you try both.
Adapted to capture the dim light of the woodland understory, the leaves of smooth hydrangea stay dark green and bold all season long. The broad leaves create a perfect backdrop to the glistening white flowers that stand out like sugar-coated confections on a green velvet background.
Smooth hydrangea fits in with nearly any style of garden, whether formal or relaxed, and looks good with nearly any other garden plant. Shade-loving plants with delicate foliage would complement the broad leaves of smooth hydrangea, so be sure to include Christmas fern, Solomon’s seal, goats beard and black cohosh into the border.
[Editor’s note: best availability on these perennials at Behnke’s is in mid-spring.]
Plants with white variegation in their leaves will nicely reflect and draw attention to the white blooms of smooth hydrangea. For a stunning combination, try planting variegated Solomon’s seal (Polygonatum odoratum variegatum) in front of smooth hydrangea.
Caring for ‘Smooth’ Hydrangeas
In addition to being beautiful, smooth hydrangea is also easy to care for. The shrub likes moist soil and will illustrate its displeasure at dry soil by wilting its bold leaves. However, usually within minutes of a quick soak from the hose, the plants perk up and, once they are established, are able to withstand drier soils. A hearty helping of Leafgro, Complete Planting Mix, or compost mixed into the garden soil during planting, and a two-inch layer of mulch on top annually, will help keep plants healthy and roots cool and moist during the hot summer months.
If plants get leggy, branches can be trimmed to the ground in fall after the leaves drop off. Since smooth hydrangea produces its blossoms on new growth, you won’t have to worry about sacrificing flowers for form when pruning.
So no matter what style your garden is, smooth hydrangea is an easy native plant that will complement your shady borders and add a touch of delicious charm to your garden.
By Natalie Brewer, Howard County Master Gardener