Recently, Chris of Backyard Gardening Blog published a timeline in pictures, demonstrating the growth of his ‘Endless Summer’ hydrangeas. I found it very interesting to compare his photos with the few I took. You might want to have his post open in a separate tab of your browser so you can quickly flip back and forth to compare shrubs.

May 13, 2007. 'Endless Summer' is just getting started.

June 4, 2007, a bit more than 3 weeks from the previous photo.

June 25, 2008. Click to enlarge photo if necessary.

July 6, 2008

July 16, 2008

July 27, 2008: fully colored up.

September 8, 2008.

Microclimates are important

Chris is in Zone 5. Theoretically I am, too, though not too long ago I would have said I was in Zone 4. I still have a Zone 4 growing season, with later spring frosts and earlier fall frosts. And Chris has one other advantage. Did you notice it? That stone wall behind his hydrangeas is providing a warmer microclimate by storing heat and radiating it back when the temperatures drop.

I have to say I was much happier with my ‘Endless Summer’ hydrangea this year than I was last year. I’m sure it improved its performance that I took care to mulch it with leaves last fall, and I didn’t pull them away from the plant until I was sure all danger of frost had passed. But I can also see that Chris gets more bloom from his ‘Endless Summer’ hydrangeas with the same amount of work.

I hope you found this comparison as informative as I did. A few extra weeks at each end of the growing season and a more favorable microclimate can make a significant difference in the performance of a plant. It’s a good thing to keep in mind when a fellow gardener rants–or raves–about a plant.

This year, my Endless Summer hydrangea is blooming abundantly.

What I did differently

As I mentioned earlier this year, I covered the shrub with fallen leaves in late autumn. I made sure they filled the center of the plant and covered the surrounding soil to a depth of six inches. I did not remove these leaves until I was certain the last frost had passed. New growth had already begun under the leaves. (I also saw some vole tunnels, which I filled in. The shrub didn’t seem to have been harmed.)

When I removed the leaf mulch this spring, I also fertilized with Shrubs Alive! Fertilizer for Acid Loving Plants, to try to enhance the blue color of the flowers. I think they are bluer than when they last bloomed, though not as blue as in the marketing photos.

I also made sure the hydrangea had better weather this year. Seriously, the weather can have a major impact on the performance of these shrubs, and there’s not much you can do about it. This was a good year for hydrangeas, and I’m thankful for it.

Unfortunately, the ‘Forever & Ever Double Pink’ that I fell in love with seems to have expired. After its stunted growth last year and its very weak growth this spring, I’m wondering if it had a virus. On the other hand, the original Forever & Ever Hydrangea (a single pink) had never bloomed for me before, and it now has buds on it. You win some, you lose some.

They’re still high maintenance

The same caveats still apply. They need their mulch in winter, they need their water in summer. Not too hot, not too cold. Ju-u-ust right. Like Goldilocks.

Endless Summer Hydrangea: Dream Come True–or Nightmare?

Hydrangea ‘Forever & Ever Double Pink’ stole my heart in 2006. This photo was taken September 7 of that year

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.

This photo of ‘Double Pink Forever’ hydrangea was taken September 14, 2007. It never got any taller, and never bloomed.

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

That’s just the high points of his excellent advice. Make sure you read the whole article. You will probably also find this forum thread of interest.

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.