By Connie Espinoza
UCCE Master Gardener
Hydrangeas are some of the most beautiful flowering plants. Hydrangeas offer big, beautiful leaves and large clusters of long-lasting flowers in shades of white, pink, and blue. Garden hydrangeas (Hydrangea macrophylla) are nicknamed mopheads and lacecaps after the shape of their blossoms.
Hydrangeas are generally easy to grow and are resistant to most pests and diseases. Although their showy blooms make them very attractive to gardeners, it’s important to remember that most varieties are not drought tolerant in our Central Valley climate. It’s best to plant in a shadier spot of your garden where they’ll receive morning sun but afternoon shade. You’ll also have to monitor their water and during the hottest days, they might need a deep soaking. I like to plant mine in large pots (24+ inch pots) under a patio, where I can more easily control the sun and moisture they receive.
Hydrangeas typically prefer rich, moist soil that drains easily. Amending the soil with compost prior to planting is recommended. Hydrangeas should be grown in zones 3 – 9 for best results.
Hydrangea planting can be done in spring or fall. Hydrangeas are deciduous shrubs, which means they will go dormant and lose all their leaves during the winter. A fall planting will allow the plant to concentrate its energy on a strong root system, making it more able to withstand some summer heat. Water thoroughly after planting and then add a layer of mulch.
Plant in a hole as wide as the nursery container, or even a little wider, leaving an inch or two of the crown above the soil level. When planting, fill the hole half way up with soil and water it. When the water is absorbed, fill the rest of the hole and water thoroughly. Space plants 3-10 feet apart.
Hydrangea Care Guide
Water is an important factor when tending hydrangeas. They enjoy deep watering at least once a week, especially in hot, dry weather. Hydrangeas also do better with a bit of all purpose fertilizer once or twice a year in spring or summer.
Hydrangeas can also be transplanted easily, but this should only be done during dormancy in fall or winter. Be sure to dig up the entire rootball and replant immediately.
Hydrangea types and varieties
The most common types of hydrangea are the Mopheads and Lacecaps (Hydrangea macrophylla). Mopheads are the varieties with large, globe-shaped clusters of flowers that many of us remember as kids. Lacecaps have flat heads featuring a central area of tiny flowers and an outer ring of large, showy ones. H. macrophylla ‘Variegata’ or Tricolor, has beautiful green and white variegated foliage to brighten a shady corner.
The Oakleaf hydrangea (H. quercifolia) is the more drought-tolerant variety, which might make it more suitable to the Central Valley garden. With its unique fall color and oakleaf-shaped foliage, this variety usually provides year-round interest. It prefers medium moisture, but when established, will hold up to dry weather.
Panicle varities (H. paniculata) have flowers in cone-shaped clusters, rather than ball-shaped. Their leaves are smaller, thinner, and rougher than leaves of the mophead hydrangea. ‘Grandiflora’, commonly known as Pee Gee, exhibits white flowers in summer, which slowly age to pink and finally fade to brown or tan, persisting well into the fall.
H. arborescens, also called wild or smooth hydrangeas, are native to the United States. The leaves of arborescens are generally heart-shaped, thin, and floppier than the mopheads and lacecaps. ‘Grandiflora’, or Hills of Snow hydrangea, produces large showy white flowers in late May to June for up to two months.
The hydrangea vine or climbing hydrangea (H. anomala) has fragrant white flowers in flat-topped clusters (to 8” wide) that bloom in late spring to early summer. These vines can grow from 30-80 feet tall. Climbing Hydrangea requires little to no pruning, but if you need to trim it to keep it in bounds, you should prune it just after flowering. Cut back last year’s flower shoots to 1 to 2 inches.
Change the color of hydrangeas
An interesting aspect of H. macrophylla is that it is possible to change the color of its blooms from pink to blue. This is done by manipulating the soil’s pH level. To change the blooms to blue the soil must be acidic with a pH of 5.5 or less. This can be done in several ways and can be time-consuming. Pink hydrangeas can be turned blue by applying aluminum sulfate to lower the pH and add aluminum to the soil. Applying lime to raise the pH level will help blue hydrangeas turn pink. For more information, check our article archives: https://ucanr.edu/datastoreFiles/268-73.pdf
White blooms are not affected by pH. When attempting to change the colors, always give the plant at least a few weeks of rest time before making a switch.
Pruning care for hydrangeas
In order to know when to prune your hydrangea, one must first identify the species.
H. macrophylla and H. quercifolia both bloom on old wood and require little pruning. Prune spent blooms immediately after flowering (midsummer), or remove only dead, damaged or unsightly wood. Old wood are stems that have been on the plant for at least nine to ten months before the hydrangea blooms. The buds form on the stems around August through October for the following spring. If these stems are removed or pruned in the fall or winter, the bloom buds for the spring will be removed and there will be little or no bloom the next year.
H. arborescens and H. paniculata both bloom on new wood and actually produce larger blooms if cut back to the ground in late winter. You may also choose to prune these bushes back to 2-3 feet in early spring.
Hydrangeas are worth the extra care and maintenance because of their beautiful blooms. With proper care and culture, these beautiful bushes will reward you each year with magnificent blooms.
The UCCE Master Gardeners will be available to answer your gardening questions each Saturday at the Visalia Farmer’s Market in the Sears parking lot from 8 to 11 a.m.