Seek out hydrangeas for summer-flowering shrubs

Many believe that “hydrangea hysteria” erupted in 2004 with the debut of the reblooming bigleaf hydrangea, ‘Bailmer,’ known by its trade name of Endless Summer™. Since this mophead hydrangea cultivar entered the marketplace, the interest in mophead and lacecap hydrangeas skyrocketed, especially remontant or reblooming types. This frenzy to produce bigger-flowered, smaller-statured, more floriferous hydrangeas caused the number of Hydrangea macrophylla cultivars to swell to more than 300 and counting.

Hysterical hydrangea breeders diverted their attention to other species, notably the native, white-flowered smooth hydrangea (Hydrangea arborescens), which gave rise to the pink-flowered Invincibelle™ Spirit ‘NCHA1’ in 2010 and the new-and-improved Invincibelle™ Spirit II (‘NCHA2’) this past Spring.

Even the often maligned panicled hydrangea drew attention from plant breeders, who looked past its gawky, gangly stature (15 to 25 ft. high and 10 to 20 ft. wide) and homed in on its large mid-summer white panicles, preference for full sun, and tolerance to drought. Their breeding efforts led to a wide range of cultivars boasting a variety of shapes and sizes that include ‘Bulk’ (Quickfire™), ‘Phantom’, and ‘Tardiva’.

Despite these contenders, the beloved bigleaf hydrangea has no rivals. While visiting the hydrangea collection at the SC Botanic Garden this past week, I can see why. There are mopheads with cabbage-sized blooms and dainty, more refined-looking lacecaps with flattened, disk-shaped inflorescences. On many bigleaf hydrangea cultivars, their flowers are either blue or pink depending on the level of aluminum that’s available in the soil, which is dictated by the soil pH. For blue flowers on your mophead and lacecap or French hydrangeas, maintain a soil pH between 5 and 5.5. An acid soil increases the availability of aluminum, which turns the flowers blue. Apply sulfur to reduce the pH to this ideal range in late summer or when you see new growth emerging in the Spring.  To avoid having to adjust the pH, grow a blue-flowered hydrangea such as ‘All Summer Beauty’, ‘Blue Wave’, or ‘Nikko Blue’.

Pink flowers occur on bigleaf and lacecap hydrangeas with a soil pH between 6.0 and 6.5. In this pH range, aluminum becomes “tied up” or rendered unavailable in the soil and so is absent from the flowers. Use lime to increase the soil pH to this desirable range. To avoid having to maintain a particular pH, grow pink-flowering cultivars such as ‘Forever Pink’ and ‘Pia’.

Hydrangea macrophylla 'Goliath' SCBG 6_3_2016

The cultivar ‘Goliath’ is an old-timey bigleaf hydrangea from Germany that produces bouquet-sized blooms that range in color from deep pink to purplish-blue. June 8, 2015. SC Botanical Garden, Clemson, SC.

Some cultivars produce a kaleidoscope of colors, such as ‘Goliath’, which is perfect for people who aren’t sure if they want pink, blue, or blurple (a combination of pink and blue) hydrangea flowers.

If you have a landscape with high, filtered shade or a site that receives morning sun and afternoon shade, grow hydrangeas. Dr. Michael Dirr, renowned plantsman and author of Dirr’s Encyclopedia of Trees & Shrubs (Timber Press, 2011), evaluated over 250 cultivars of Hydrangea macrophylla in Athens, Georgia, and created two lists of favorites.  His “historical” favorites include ‘All Summer Beauty’ (mh = mophead), ‘Ami Pasquier (mh), ‘Blue Wave’ (lc = lace cap , Frillibet (mh), Generale Vicomtesse de Vibraye’ (mh), ‘Lanarth White’ (lc), ‘Lilacina’ (lc), ‘Mme. Emile Mouillere’ (mh), ‘Mousseline (mh), Nikko Blue’, (mh), ‘Veitchii (lc), and ‘White Wave’ (mh). His list of reblooming bigleaf hydrangeas include ‘Blushing Bride’ (mh), ‘David Ramsey (mh), ‘Decatur Blue’ (mh), Endless Summer® (mh), ‘Mini Penny’ (mh), ‘Oak Hill’ (mh), ‘Penny Mac’ (mh), and Twist-n-Shout™ (lc).

You don’t have to take his word for it. In the hydrangea collection at the SC Botanic Garden there are 39 cultivars of bigleaf hydrangeas in bloom right now, and more than 30 cultivars of mountain hydrangea, oakleaf hydrangea, smooth, and panicled hydrangea. This team of 5 hydrangeas will provide color in your garden from May to late September, and will always give you an excuse to go outside for a spell. If the heat and humidity is not to your liking, you can always enjoy them as cut flowers indoors.

Bob Polomski  © 2016

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s