The Iowa Gardener: Picking the best hydrangeas for Iowa

Who can resist big, bodacious hydrangeas? Just be sure to plant those types that will succeed in our cold climate.

Hydrangeas are all the rage in garden centers right now. With their melon-sized clusters of flowers in pink, blue, and white, these small shrubs are stunners. Bonus: They thrive in light shade.

However, not all types of hydrangeas do well in Iowa. Steer away from types that won't flower and instead, spend your garden dollars on those that will.

The Big Blue

Blue hydrangeas are known as Mophead hydrangea (Hydrangea macrophylla), also called big leaf or French hydrangea. They are drop-dead gorgeous when in bloom in garden centers. But they've been babied to flower beautifully one time in order to lure you into buying. They're gorgeous naturally in some parts of the country, especially in the moist, highly acid soils of the East Coast. In less acidic soils, the flowers bloom pink. (Note: Soil acidity or adding sulfur will make some pink hydrangeas bloom blue; but it will not make white types bloom pink or blue. Acidity has no effect on the actual production of flowers, only on the range of pink to blue.)

Here in the Hawkeye State, Mophead hydrangeas will grow healthy, attractive foliage, but our Iowa late spring frosts zap developing flowers. Some Iowa gardeners, if they're lucky, get a few puny mauve-colored flowers now and again.

So, bottom line: The blue-type hydrangeas are not a recommended plant for Iowa. You'll get nice foliage but next to no flowers.

‘Endless Summer' Hydrangeas

The good news is that there is a new type of hydrangea, Endless Summer, bred in Minnesota, that has promise for Iowa. It produces flowers like the sky blue types, though they tend to be more pink or mauve. However, this plant is relatively new and I feel the jury still is out. I have one and it struggles year after year. Last year, after five years, I finally got a few small pinky-lavender flowers.

Like mop-head types, Endless Summer grows about 3 feet tall and wide.

Other Better Choices

There are some hydrangeas that do really well in Iowa and are very pretty.

The Annabelle hydrangea grows 3 to 5 feet tall and gets large creamy flowers also the size of melons. The flowers will dry right on the plant (or in a vase) to a pretty buff color and last for months.

Annabelle is one of the smooth hydrangeas (Hydrangea arborescens). Like all hydrangeas, it likes moist soil. It will do well in light shade, but also in full sun.

Also experiment with the panicle hydrangea (Hydrangea paniculata). It has large, cone-shaped creamy white flowers that also lasts a long time. It will reach as high as 10 feet. Try Grandiflora or PeeGee, two of the most popular cultivars.

Pruning Hydrangeas

There's a lot of confusion about pruning hydrangeas. But in Iowa, pruning hydrangeas is pretty simple. (It's only in warmer climates that you have to be careful about timing.)

If you do have a Mophead hydrangea, prune it as little as possible in our climate. In late May, after it has leafed out, if there's any dead stuff, trim it out and be done with it.

With other hydrangeas, cut out any obviously dead wood in late April or early May, when the stems are leafing out. Otherwise, cut them back - only as needed - in July or so after they're done blooming.

That, in fact, is a good rule of thumb for all flowering shrubs: Prune them right after they're done blooming. That way, you never have to worry about harming developing flowers.

l Veronica Lorson Fowler is co-publisher of the website, theiowagardener.com