While Southerners may not be able to enjoy wondrous lilacs, they do grow the best hydrangeas! In fact, the shaggy flowers of mophead hydrangeas (pronounced hī dran' ja) are a must-have plant for many gardeners.

Blue hydrangea

Blue-flowering hydrangeas occur in soils with low pH and aluminum.

Photo Credit: Lane Greer

Pink hydrangea

Pink-flowering hydrangeas bloom in soils with higher pH levels.

Photo Credit: Lane Greer

Blue hydrangea

No matter what color they are, hydrangeas add beautiful summer blooms to your garden.

Photo Credit: Lane Greer

Purple hydrangea

One of the most popular hydrangea colors right now is purple.

Photo Credit: Lane Greer

There are two kinds of bigleaf hydrangeas (Hydrangea macrophylla): mopheads (sometimes called hortensias) and lacecaps, which have a much flatter flower. Mopheads sport huge blooms that stretch up to 12 inches across. These marvelous shrubs are hardy in zones 6 through 9, and they grow especially well in coastal and mild climates.

These old-fashioned favorites look wonderful in shade. Plant them under deciduous trees or on the north side of a house or building about 5 feet apart for bursts of color. Some selections grow up to 8 feet tall. But if you’ve got a smaller space you’d like to add these beauties to, try one of the many compact forms great for patio pots or other containers.

The No. 1 question about mophead hydrangeas is not which one to choose (there are so many greats), but it’s how to change their color. Bloom color depends on soil pH level, as well as the availability of aluminum in the soil. Acidic soils (those with low pH) with sufficient aluminum produce blue flowers. Alkaline soils (with a high pH, such as on limestone) create pink flowers. Some hydrangeas are “red” (actually a very dark pink), and planting these in acidic soils causes them to turn purple. Green hydrangeas “bloom” in late summer and fall, as they are actually older flowers. They often have tints of purple, blue or red on their petal (technically these are sepal) margins and you may hear people call them “antiques.”

When it comes to soils, hydrangeas can grow on most any kind – but not as well on heavy clays. Add compost to the soil at planting, as well as a slow-release plant food like Osmocote® to be sure your hydrangeas receive the right amount of nutrients they need to thrive at the right time. Mulch afterward to keep plants looking their best. And remember, these beauties need lots of water, so plan to irrigate them, particularly when they are young.

In some areas of their hardiness range, hydrangeas bloom reliably every year. But regions with “difficult” winter and spring weather may have hydrangeas that flower inconsistently.

If your garden falls in the areas with harsher weather, there’s good news. Some new kids on the block are truly different because they bloom every year, like Endless Summer®. Because most hydrangeas set their flower buds the year before they bloom, pruning them back in winter or spring will remove the flowers for the next year. But remonant (or reblooming) hydrangeas like Endless Summer bloom on the current year’s wood, so they’ll have flowers in summer regardless of pruning or bad winter weather. Other great but less-known remonant bloomers include ‘Blushing Bride’, ‘David Ramsey’, ‘Decatur Blue’, ‘Oak Hill’ and ‘Penny Mac’.

With the advent of new remonant types and a better understanding of how to change hydrangea color, more gardeners can enjoy all the beauty these wonderful shrubs bring to the shady places of their garden.