There’s no doubt that the past winter left its mark on some plants in our gardens:  outright mortality in more than a few cases and many instances of delay in leafing out of woody plants.  The branches are green and the leaves are trying to push out but we have had to play the waiting game to see whether the plant is going to come back.
The Hydrangea macrophylla, or mophead hydrangea, are one of the plants that were battered by the cold snap in November.  I’ve talked to numerous customers who report very slow growth and many dead stems.  It’s a bit disappointing, but what can you do?  Some of these plants will likely not bloom, having suffered too much damage to the stems to produce flowering wood this growing season.
What if there was a mophead hydrangea that was hardy enough to withstand even colder winters, down to Zone 4?  Wouldn’t it be great if the large, round blossoms were produced early in the season and right through until frost in the fall, without any dieback to recover from?  There is a hydrangea with these characteristics-Hydrangea macrophylla ‘Endless Summer.’
Endless Summer was discovered growing in a neighbourhood in St. Paul, Minnesota, where winter temperatures can reach -40 deg. C.  Further breeding by Bailey Nurseries and renowned plantsman Michael Dirr has given gardeners a plant that seems too good to be true; a hardy mophead hydrangea that blooms on old wood produced the previous growing season and on new wood during the present season.
Flowers of blue or pink (depending on the acidity of your soil-blue in acidic soil and pink in alkaline) are present from early summer until the fall, as Endless Summer blooms on the terminal buds at the ends of its stems, and also on the basal buds along the branches and down near the plant’s crown.
Although this flowering habit is quite unique among hydrangeas, caring for Endless Summer is similar to other macrophylla types.  These hydrangeas like a moderate temperature throughout the day, with even moisture.  Subjecting them to baking hot daytime highs and allowing them to dry out will no doubt result in an unhappy plant.
Site them where they will enjoy some relief from the afternoon heat and give them a good, rich soil well amended with organic matter.  A mulch of shredded bark or pine needles will keep the roots cool and conserve moisture in the soil.  Remember that all mophead hydrangeas are slow to establish in gardens in colder climates, but once they are settled in Endless Summer will give you unmatched performance in the shadier and cooler parts of your landscape.
Endless Summer matures at between two and four feet high and wide.  It can be planted with lower growing variegated shade plants such as Pulmonaria (Lungwort), Hosta and Polemonium (Jacob’s Ladder).  Or combine it with shade tolerant annuals like impatiens, begonias, torenia and lobelia.