Hydrangea helper

Hydrangeas are stellar shrubs for Minnesota. In late summer, just when many other flowers are fading, the big, beautiful blooms of hydrangeas are coming into their own. And with the right care, these lush plants can keep their looks well into fall.

Hydrangeas aren't high-maintenance plants, but the three basic types do have different growing habits and care requirements. This quick primer will help you decide which hydrangea would be best suited for your yard.

Smooth hydrangea (Hydrangea aborescens)

This hardy, compact shrub grows to 3 to 5 feet tall and forms large rounded flower clusters that are referred to as lollipops by some gardeners. Although the flowers form in early spring, they look their best in August and September. That's because they start out a pale green color and turn white only later in the season. The flowers, which dry and remain on the stems, can be cut for fall or winter arrangements.

Native to much of the eastern United States, smooth hydrangea is hardy to zone 3. Because its flowers form on new wood (the current season's stems), the flower buds are not affected by winter.

Best in: Partial shade to full sun. Although it prefers moist, well-drained soil, smooth hydrangea can tolerate a range of soil conditions.

Prune: In the spring before growth starts, prune last year's stems to 1/2 inch above the first pair of buds. If more pruning is needed, wait until after the shrub has flowered in late summer or early fall.

The tallest of the hydrangeas, panicle hydrangea grows to 8 to 10 feet high. This multi-stemmed shrub often is pruned into a single-stem small tree. Panicle hydrangea has large and lovely cone-shaped flower clusters. In many cultivars, the clusters are made up of a mix of large and small florets, which gives them a lacy look. The most common cultivar, PeeGee (Hydrangea paniculata 'Grandiflora'), has flowers that open white in August and turn pink or purplish as they age.

Best in: Partial shade to full sun. Although it prefers moist, well-drained soil, it can tolerate a range of soil conditions.

Prune: Like smooth hydrangea, panicle flowers on the current season's stems. Pruning out some of the branches will result in fewer, but larger flowers. But prune only after the plants are finished blooming in late summer or fall.

Big leaf hydrangea (Hydrangea macrophylla)

This coveted hydrangea makes up in color what it lacks in size. Although the plant only grows to 2 or 3 feet tall, it has large blue or pink flower heads. Until fairly recently, few big leaf hydrangeas would flower in Minnesota. (The plants would survive, but the flowers often winter killed because they formed the previous summer.) But in 2003, Bailey Nurseries introduced Endless Summer, a hardy big leaf hydrangea that blooms on new and old wood. Now, there are three cultivars in the Endless Summer series, including Endless Summer Blushing Bride, which has white flowers with a blush of pink, and Endless Summer Twist and Shout, which has a mix of large and small florets in pink or blue.

Prune: This short plant, which dies back to the ground in winter, rarely needs pruning except to remove dead stems.

Forever blue: Most Endless Summer and Twist and Shout hydrangeas are sold with blue flowers, but the soil must remain acidic for the flowers to continue to be blue rather than turn pink. Minnesota is known for alkaline soil, so you may have to amend the soil to keep your big leafs blue. For how-to information, go to www.extension.umn.edu/yardandgarden/YGLNews/YGLNews-May1506.html.

Mary Hockenberry Meyer is a professor and Extension Horticulturist with the University of Minnesota.