Hydrangea: Stars of the Season

Hydrangeas herald the peak of summer, but that long-awaited heat brings out much more in our gardens.

Credit: Courtesy of Endless Summer

Hydrangeas herald the peak of summer, but that long-awaited heat brings out much more in our gardens

There are two very common complaints in regards to hydrangea: Shrubs that lack flowers or shrubs that outgrow their allotted space. These problems are often linked, as mophead or Hydrangea macrophylla types generally bloom from the previous year’s tip buds, many of which are pruned off in spring to reduce the size of the shrub. Choosing compact cultivars such as ‘Pia’ (60 cm/2 ft. tall) or ‘Adria’ (90 cm/3 ft. tall) to fill in smaller garden spaces will solve these issues.

Protect hydrangea through winter

Winter damage is another problem that can be somewhat alleviated by leaving last year’s faded blooms over winter to protect the flowerbuds immediately below. Another option is to consider remontant, or repeat-blooming, hydrangeas like the Endless Summer® series or ‘Penny Mac’; these bloom on both old and ripened new wood. Despite the common name, H. macrophylla comes in both mophead (‘Forever Pink’) and lacecap (‘Blaumeise’ or ‘Teller’s Blue’) forms.

Hydrangea flower colour

The other quirk to remember with this species is that with the exception of white cultivars, flower colour can change with the pH of the soil. Soil pH determines the availability of aluminum which is part of the flower’s blue pigment. To encourage blue flowers, add aluminum sulfate according to package directions. Also, use a fertilizer low in phosphorus and high in potassium. For pink flowers, add dolomite lime twice a year to make the soil less acidic.

Clematis 'Ville de Lyon
Clematis ‘Ville de Lyon
Courtesy of Clearview Horticultural Products

Different species of hydrangea

There are so many great species of hydrangea out there that I would be remiss if I didn’t at least mention a few of my favourites. For reliable blooms on new wood, try H. arborescens ‘Annabelle’ (white), or one of the many H. paniculata cultivars, such as ‘Kyushu’ or ‘Limelight’ (greenish-white). Gardeners with a little more shade or filtered light will find the lacecap blooms of H. serrata ‘Bluebird’ both delicate in appearance and reliable.

The summer heat also brings out the best of the perennial border – with the vibrant blooms of Achillea ‘Terracotta’, Crocosmia ‘Lucifer’ and Hemerocallis ‘Rajah’ really standing out. This is also the time when ‘C’ group clematis such as ‘Ville de Lyon’ and ‘Rouge Cardinal’ begin their summer-long flower display. And for sheer contrast, it’s hard to beat the gold foliage and rich-pink blossoms of Spiraea japonica ‘Goldflame’. Canna lilies such as ‘Wyoming’ or ‘Cleopatra’ (yellow-red blooms) also thrive in the heat, as does the bizarre-looking but always eye-catching summer annual, Amaranthus tricolor ‘Joseph’s Coat’.