FLIMBY: How to keep hydrangeas happy

This is another installment in our Flowers in My Back Yard series, dedicated to blooming plants.

Hydrangea mania has come to California.

Most of the nation has been enthralled with this nostalgic flowering shrub for at least a decade. Amid our state’s prolonged droughts, California gardeners leaned away from this notoriously high-water plant. (Hydrangea, after all, means “water vessel.”)

But new hybrid varieties that require less water while reblooming for months have broken down our resistance. There’s now a hydrangea for almost any California landscape – especially shady spots.

Nationwide, gardeners have rediscovered hydrangeas as easy-care, low-maintenance, pest-free shrubs. They “bloom” – or boast huge flowerheads – when other shrubs are basic green at best. (And some species change color!)

White Flower Farm, which sells more than 60 varieties from its Connecticut-based nursery, explains:

“Hydrangeas bloom throughout summer and fall – a quiet time for most woody plants. Hardy, and pest-free, they’re suitable for a broad range of climatic conditions and are particularly tolerant of both wind and salt spray, which makes them an ideal choice for seaside addresses. Colorful, versatile, and easy-care, they’re among the most valuable of garden shrubs. Available in a range of colors, forms, and sizes, the smaller varieties can be planted in container pots or used to fill spaces in mixed borders. Larger specimens bring seasonal color to foundation plantings and make stunning backdrops in a mixed border. Planted in groups, they are also superb, long-blooming hedges.”

Hydrangea hybrids such as Proven Winners’ “Let’s Dance” series have been repeatedly voted favorite new shrub by gardeners. They offer all those hydrangea positives plus the ability to rebloom on new wood.

That’s a major difference; most hydrangeas bloom on “old wood” – stems that grew the summer before. (And is a clue to why some hydrangeas don’t consistently bloom.)

Like other plants enjoying a resurgence in popularity, hydrangeas evoke memories. A staple of Eastern and Midwestern gardens, these long-flowering shrubs came to California sometime around the Gold Rush and have been here ever since.

Native to Asia and the Americas, more than 70 species of hydrangeas have been identified. Europeans called the familiar mophead varieties Hortensia before hydrangea caught on. Most common varieties are deciduous.

Mopheads and lacecaps are the most familiar and cultivated varieties. With very distinctive flower forms and looks, they’re actually two faces of the same species: Hydrangea macrophylla. These hydrangeas also are most sensitive to water loss; they lose moisture via those big leaves.

Each has their preferred landscape use. With a more traditional look, mopheads make great foundation plants with masses of blooms. Reflecting their nickname, lacecaps look more informal and a little wild. Both can grow big (over 8 feet tall) if given enough water. Restricting their irrigation helps limit their growth. (Some new dwarf hybrids stay under 2 feet tall and wide.)

Lacecaps are actually preferred for pollinator gardens; their tight little center flowers offer more food as well as easy landing zones, according to Wayside Gardens, another hydrangea supplier.

Both mopheads and lacecaps may change color, reflecting soil acidity. (It’s actually aluminum absorption that’s impacting those hues.) The more acid (or lower pH) the soil, the bluer the hue; generally, blue hydrangeas need pH below 5.5. In more alkaline soils (above 6.5), the flowers veer pink. Balanced soil (5.5 to 6.5) results in lavender and purple hues.

One bush can contain blue, pink and lavender flowers, depending on soil conditions around its roots. Aluminum sulfate added to the soil can help maintain that bright blue color. (Pine needle mulch works, too.)

The brightness or intensity of those colors depends on saturation; that varies by hybrid. Hydrangeas with the darkest hues (such as some intense pinks or purples) have the highest saturation. Most of these flowerheads gradually fade to shades of pale green as they age.

White hydrangeas do not change color because their petals don’t contain the needed pigments.

Mountain hydrangeas (H. serrata), a Japanese native, look a lot like lacecaps, only more compact and better behaved. (They also change color depending on soil acidity.) Several new hybrids cross big-leaf macrophylla and lacy serrata varieties to get the best traits of both.

Gaining in popularity (particularly in low-water gardens) are smooth-leaf hydrangeas (H. arborescens). These woody stemmed hydrangeas can have huge, usually pure white or lime green flowerheads; ‘Incrediball’ measures more than 12 inches across. Their “smooth” leaves actually feel velvety, and tend to lose less moisture than mopheads or lacecaps. And they require only twice-monthly irrigation. (Big-leaved varieties need at least weekly water; more during July and August heat.)