Few plants have become as recognizable in garden centers as Endless Summer Hydrangeas, in their blue pots and colorful ball-shaped blossoms. What started as one Endless Summer Hydrangea type with blue flowers has now become the Endless Summer Series, with four members: Original (blue flowers), Twist ‘n Shout (pink), Blushing Bride (white with pink blush), and Bloomstruck (purplish).
They’re beautiful, but will they grow here? Let’s start by saying the best-suited hydrangeas (meaning winter-hardy and requiring no extra measures for survival) for North Dakota and Northern Minnesota belong to two species. Hydrangea arborescens types are fully adapted, like the large-flowered white Annabelle. Hydrangea paniculata types are also well-adapted, with their pyramidal-shaped flower clusters, like Vanilla Strawberry. (See photos below.) Key words are the species H. arborescens and H. paniculata, which can be located in fine print on the plant labels, along with the cultivar name.
Endless Summer hydrangeas belong to a different species, more closely related to the florist hydrangea, Hydrangea macrophylla. They aren’t as totally suited to North Dakota and Northern Minnesota as the two Hydrangea species mentioned. If you look at the label closely on Endless Summer, you’ll see the botanical species Hydrangea macrophylla. They are distinctly borderline in adaptation for our region.
Because they are so widely sold in the region, two years ago I did a fairly extensive survey to see if gardeners were having success with Endless Summer. More respondents reported failure than reported success, saying the hydrangeas did fine the first summer, but failed to survive winter, or gradually went downhill.
However, a few people reported success, and were enjoying Endless Summer. Those who were successfully growing Endless Summer for multiple years were doing several things in common:
- They were planting Endless Summer in a protected microclimate within a sheltered yard, not in a windswept, open area. Best location was in shade, or a little morning, east sun. Not hot, dry location. Locations with good winter snow cover were more successful.
- Successful growers were keeping them very moist, many with soaker hoses that could be turned on frequently.
- Mulching with wood product mulch during the summer to keep soil cool and moist.
- Fertilizing with Miracid or hydrangea fertilizer.
- A key point with most successful growers was mulching the plants with wood chips for winter protection, by mounding them up in fall, then leveling out the mulch for summer moisture conservation.
If left to their own devices, or planted and grown as we would ‘ordinary’ shrubs, most people reported failure after a season or two.
In summary, for successful growing of Endless Summer Hydrangeas, a fair track record of experience shows that extra steps are needed in North Dakota and Northern Minnesota. They can be grown, and grown beautifully, but buyers should know the difference between the better-adapted types and the Endless Summer types, which need some extra TLC.
Below are photos of several well-adapted hydrangea examples. Happy Gardening!