Today's hardy hydrangeas give Minnesota gardeners more blooming options

When the hydrangea Endless Summer was released in 2003, Minnesota gardeners were ecstatic at the chance to grow something other than the white hydrangeas we were used to.

If the soil was acidic enough, Endless Summer produced bright blue flowers. If it wasn't, the flowers were a soft pink or lavender.

At the time, that was enough for me. I liked Endless Summer's attractive dark green leaves. The plant was a solid presence in my perennial bed, even if in some years it didn't bloom much.

But over time, I've tired of babying Endless Summer. Every fall I cover it with leaves to protect it through the winter. One year, when it seemed spring was really here, I stripped off the protective mulch, only to have a killing frost hit the area. That year, Endless Summer was a barely visible green bump in the garden.

While I haven't gotten rid of my Endless Summer yet, there are far hardier hydrangea choices for Minnesota gardeners today. And there's no better place to see them than in the hydrangea trial garden at the Minnesota Landscape Arboretum in Chaska.

The garden is part of a national plant-trial program called Earth-Kind that is being used to see how hydrangeas do under low-maintenance conditions. The plants are watered their first summer in the ground, but after that they're on their own unless there's a severe drought. The plants are mulched but not fertilized. It's basically survival of the fittest.

I visited the arboretum a few days ago to take a look at the trial plot, where about 20 hydrangea varieties are planted in four beds. If you're thinking about adding hydrangeas to your landscape, now's the time to take a look at them. While many of the plants were just past peak bloom, most still had newer flowers so you can see their color and shape.

Limelight and Little Lime, which feature white flowers that age to green, were covered in dozens of flowers that on some plants nearly hid the leaves. Pinky Winky, Quick Fire and Vanilla Strawberry stood tall and straight with large conical flowers that start white and grow an intense pink with age. At midseason, these hydrangeas often have new white flowers and older pink blooms at the same time, making a striking display. Some hydrangeas in the trial garden flopped under the weight of their flowers, but these three have thick, strong stems that hold blooms upright.

All the above varieties are panicle hydrangeas, which are winter hardy to Zone 3, north of the Twin Cities. They're brawnier, coarser-looking plants than big-leaf hydrangeas like Endless Summer, growing rapidly in the spring and blooming on new wood. Panicle hydrangeas can reach heights of 8 feet or more.

In the trial garden, big-leaf hydrangeas like Endless Summer and its newer relative, Twist-n-Shout, looked healthy and green but had few flowers. Both were less than 3 feet high. Twist-n-Shout had more flowers than Endless Summer, with deep blue and pink blooms on the same plant. The leaves were flushed with maroon. Twist-n-Shout is a lacecap hydrangea, with flower heads that combine large individual flowers with little buds that stay small.

The hydrangea trial garden is in full sun. While hydrangeas traditionally are considered partial shade plants, in Minnesota panicle hydrangeas do just fine and flower more heavily in full sun. Big-leaf hydrangeas like Endless Summer, which wilt dramatically when dry, may need a more sheltered spot.

If your heart is set on having a blue-flowered hydrangea in your Minnesota garden, you'll have to stick with certain big-leaf hydrangeas and be willing to amend the soil to maintain the blue color. Altering soil acidity can be a laborious process, and quick treatments run the risk of poisoning the soil, so care is needed. Here's more information from the University of Minnesota Extension Service:

After I lost a maple tree this year, I planted two Pinky Winky hydrangeas as foundation plants in my east-facing front yard. While they can't replace the enormous tree as a landscape feature, I'm excited to see how these sturdy shrubs with white blooms that age to pink look against my gray house as they get bigger each year.

As for Endless Summer, this year the leaves provided nice texture in the perennial border but the plant had just two flowers. I'm reluctant to give up a plant I've had for 10 years, but I think that unless Endless Summer provides more of a show next year, it will make way for something new.

Mary Jane Smetanka is a Master Gardener and Minneapolis freelance writer.