Endless Summer Hydrangea: Dream Come True–or Nightmare?
It’s just like Elizabeth said. We gardeners want to believe that our dream plant is out there, just waiting for us to find it. I know when I first saw photos of the ‘Endless Summer’ hydrangea, and read that it bloomed in zone 4, I thought I’d finally be able to grow the same kind of hydrangeas my grandmother did. As you’ll read below, the truth is somewhat more complicated. The same year I got the ‘Endless Summer’ hydrangea (2006), I also received some Forever & Ever hydrangeas to trial, including this one on the left. “Trial” means it came to me straight from the grower, already forced into precocious growth, a good month before my last frost, so its behavior in my garden that first year could hardly be considered typical. My garden notebook doesn’t state when this bloomed that first year, but it was still blooming the first week in September. I fell in love with it.
The following year, in 2007, it got hit by frost after the leaves had emerged. Maybe it got knocked back twice, I don’t remember. (I may forget to cover an iffy plant once in spring, but rarely twice. But there are those nights where the temperature drops much more than predicted.) But when all danger of frost was past, and it started growing, well, it didn’t. Take a look at the photo on the right. I have never seen a woody plant do this. It put out leaves, but the stems didn’t lengthen. Seven inches was as tall as it ever got. You can see the Johnny-jump-ups towering over it in the background. (Click on image for a larger one.)
2007 was a Bad Year for these Hydrangeas
Neither ‘Endless Summer’ nor any of the Forever & Evers bloomed for me in 2007. By all accounts it was a bad year for these reblooming hydrangeas, so let’s not hold that against them.
These are not the old-fashioned hydrangeas
But it’s time to wake up and smell the coffee. Cold climate gardeners, I’m talking to you. These are not the hydrangeas you see growing and blooming in the yards of older homes. These new, fancy hydrangeas, the ‘Endless Summer’ series, the Forever&Ever series, and the Let’s Dance series are all cultivars of Hydrangea macrophylla. These hydrangeas really don’t belong here. They are at the northern limit of their hardiness. For me, at least, they break dormancy well before the last frost in spring. Yet the slightest frost will kill back all the growth, so you need to cover it in spring and fall–every time a frost threatens. Better yet, keep them heavily mulched until all danger of frost is past.
Southern hydrangeas trying to make it in the north
So why are they being marketed to Northern gardeners? Your typical macrophylla blooms on old wood. That means it forms flower buds the year before they are to bloom, and they have to survive the winter. As you might guess, that usually doesn’t happen in our climate. Enter the next generation of macrophyllas: they also bloom on new wood. Even if they die all the way back to the ground (which they will), the new branches that emerge in spring will have flower buds.
But it ‘s not that simple. According to Jim Kohut at Northscaping, our growing season is often not long enough for those buds on new wood to flower. We may get, at best, “one flush late in the season.” For a longer season of bloom, you need to mulch heavily to protect the buds further up the stems.
And that’s not all. Again, according to Jim, these plants need:
- Evenly moist soil, but no standing water
- Moderate air temps during the day
- A low nitrogen, high phosphorus (10-40-10) fertilizer–but stop before August
- Minimal pruning at first–don’t even deadhead for the first couple years
According to Tim Wood, plant hunter for Spring Meadow Nursery (Proven Winners),
If your Endless Summer dies back to the ground in the winter, forcing growth will deliver more flowers and sooner. Endless Summer and other rebloomers have to put on a certain amount of new growth before they will make new buds and flower. So it pays to give these plants extra fertilizer and water to push the growth. Miracle Grow once a week after any danger of frost does the job.
(Note: Miracle Gro is 15-30-15–proportionately more nitrogen and less phosporus than what Kohut recommends.)
Are these prima donna hydrangeas for you?
The bottom line is, you can grow these babies to at least USDA Zone 4–but you have to really want to. They are not low-maintenance shrubs in our climate; they need pampering. If, like me, they remind you of Grandma’s garden, or if you think they’re drop dead gorgeous, you’ll put in the work and be grateful that you can now grow what used to be a shrub for warmer climates.
If you’re hankering for something hardier, try:
- Hydrangea paniculata ‘Grandiflora’ (aka “Pee Gee”)
- Hydrangea arborescens ‘Annabelle’
- Hydrangea paniculata ‘Limelight’
- Hydrangea paniculata ‘Pinky Winky’
These are just some of the more well known cultivars. This Northscaping article mentions even more, plus has additional planting advice for cold climate gardeners.
This is an experiment for all of us. Please let me know in the comments which hydrangeas are working for you.