Master Gardeners: Choosing the right hydrangea for your landscape

By Michele Walfred, Sussex County Master Gardeners
Posted 6/2/23

Hydrangeas are a popular, deciduous shrub in Delaware. Five species are commonly available, of which two are native. As their name suggests, all hydrangeas love moist, well-draining soil and will …

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Master Gardeners: Choosing the right hydrangea for your landscape


Hydrangeas are a popular, deciduous shrub in Delaware. Five species are commonly available, of which two are native. As their name suggests, all hydrangeas love moist, well-draining soil and will quickly wilt in drought conditions. That’s where the commonalities end. Let’s look at the hydrangeas offered in our region and what you need to know to grow happy hydrangeas.

Native to Asia, the macrophylla or big leaf hydrangea is a familiar species available in two distinct inflorescence forms, the globular flower shape and a dainty lacecap variety with a flat center of fertile flowers surrounded by larger sterile blossoms. Macrophyllas or “macs” blossoms will emerge in May and peak in June. Traditional macs blossom on the previous year’s wood, while reblooming varieties also bloom on the current year’s growth.

Big leaf hydrangeas are primarily grown for two distinct markets. Garden centers offer cultivars with names such as Nikko Blue and Merritt’s Supreme. Named cultivars are bred to endure in landscapes and possess characteristics such as color flexibility, growth habit and cold hardiness. Most blues and pinks will shift in color, but some cultivars will not. It’s all in the genes, so reading the tag and knowing what to expect is essential.

Hydrangeas received as gift bouquets are typically not bred with resilient characteristics and are more vulnerable in the landscape to diseases and sudden frost or cold weather snaps. These hydrangeas will need protection during a late spring frost warning. Covering your shrub during these cold spells with burlap, sheets or a tablecloth is recommended.

All macs prefer morning sun and afternoon shade. They do not require pruning and perform better if left alone. If a mature shrub encroaches into a pathway or blocks a window, the pruning window is mid-July to mid-August. Pruning at any other time will affect future blossoms. Pruning errors are a primary reason macrophyllas fail to bloom.

Serrata or “mountain” hydrangea, native to the higher altitudes of Asia, are well-suited to colder weather and overwinter well in Delaware. Serratas are almost always a lacecap. These also should never be pruned. Many serrata varieties will rebloom.

Two species of hydrangeas are native to the eastern region of the US and perform well in Delaware. Quercifolia or “oakleaf” hydrangeas offer a distinct lobed-leaf shape that is stunning in autumn. The flowers are showy coned-shaped panicles that emerge in June. Blossoms typically begin as light green and transition to white or ivory and will continue to shift color as they age to pink and green before finishing as a stunning chocolate brown.

Mature oakleafs display an exfoliating bark. They are relatively disease free and can tolerate southern exposures if grown as an understory shrub with dappled shade from a taller tree.

The other native is Arboresecens, or “smooth” hydrangea. “Annabelle” is an old-fashioned cultivar. Breeders improved on this classic, and a wide array of sturdy, showy blossoms in shades of white and blush are available. Dwarf sizes are available. Arborescens attract pollinators, are pest free and perform well in our climate, tolerating partial shade or partial sun. Smooth hydrangeas also come in a lacecap form. “Haas Halo” is one creamy white cultivar that performs well for pollinators. The bees will love it.

If you need a full-sun, heat-tolerant shrub, turn to Paniculata or “panicle” hydrangeas. Panicles’ blossoms are triangular-shaped with either a round or pointy end and bloom later than other hydrangeas, emerging in July and August. Limelight is a tried-and-true favorite. Paniculatas usually start cream or white and transition in color as they age. The cultivar name will provide the hint! The shift in color from white to rose shades depends on cooler evening temperatures. Be forewarned. Delaware’s evenings may be too hot to achieve the colors we see in catalogs.

Panicles and arborescens, the only hydrangeas to prune, bloom on new wood and thrive if heavily pruned in early spring. Mid-March is an ideal time to prune paniculata and arborescens species down by at least one-third. Allow a newly purchased plant to get established for a year or two before beginning the practice of pruning back. Pruning is optional, but it invigorates the shrub. Not pruning will result in more but smaller blossoms. Decisive pruning by one-third and eliminating all weak stems will encourage grander inflorescences.

Hydrangeas benefit from ground watering, preferably in the early morning. In late summer, a fungal leaf spot disease Cercospora is common and almost unavoidable in our humid climate. While unsightly, it is not fatal to the shrub. Disposing of any fallen leaves will help prevent the spores from overwintering.

Hydrangeas benefit from a granular, slow-release fertilizer applied in early April. Hydrangeas also grow well in containers. At the end of fall, potted hydrangeas will need to overwinter in a space that will not freeze where they can go dormant. Introduce containers outside in early spring, but bring them back if lower temperatures threaten.

Since hydrangea choices vary, it is wise to read the label carefully, match the shrub’s sun and growth requirements to a fitting site in your landscape and enjoy hydrangea happiness in your home for many years.

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