How to Plant, Grow, and Care for Rough-Leaved Hydrangea

Hydrangea aspera, or rough-leaved hydrangea, is a unique member of the genus with velvety leaves and lacecap blooms that scaffold on the shrub. Rough-leaved hydrangeas highlight a woodland edge or blend among a mixed border with attractive foliage that gives way to an elegant mid-summer floral show.

These long-lived bloomers grace the display with distinctive flowers to brighten partially shaded garden zones. A single shrub is a stately specimen, with flower heads ranging from deep blue-purple to pale pink and white. In a group or mass, rough-leaved hydrangea produces prolific cascading blooms amongst lush foliage.

What is Hydrangea aspera?

Rough-leaved hydrangeas feature showy, rounded, flat-topped lacecap flower clusters. Large leaves are fuzzy on woody stems. The genus aspera is from the Latin “rough” and refers to the foliage.

These deciduous shrubs grow upright with a rounded form, reaching up to 13 feet tall and just as wide in their natural growing range. Depending on the variety, roughed-leaved species average six to eight feet tall. Their profusion of blooms and leafy backdrops make exceptional mass plantings, hedges, foundation plantings, accents, and specimens. 

H. aspera sets buds on old wood. Blooms emerge from mid-to-late summer and last into fall. Hydrangeas pair beautifully with other shade-loving perennials like hosta, ferns, tiarella, and astilbe for gorgeous multi-season combinations. The fuzzy leaves are a lovely contrast among other hydrangea species.

Rough-leaved selections are low-maintenance and carefree, growing best in partial shade, depending on climate. Plants are durable with multi-season appeal, and cultivars in unique colors and forms bring grace and elegance to shady garden spots.

Characteristics

The most distinctive features of these medium to large shrubs are their large leaves and shower of blooms. The large, lacy clusters hold small, fertile flowers at their centers. This bundle of petite blossoms is usually deep-purple blue. The fertile flowers draw pollinators as a nectar and pollen source.

Surrounding the fertile flowers is a ring of one-inch sterile pale blue-white, pink, or purple ray florets. The huge, flat heads reach up to 10 inches across in some varieties. Unlike bigleaf hydrangeas, soil pH does not affect flower color.

The woody shrubs feature soft, hairy leaves in deep green. The lance or ovate-shaped foliage grows as long as 10 inches and as broad as three. Varieties like ‘Burgundy Bliss’ have new growth that emerges purple-red, and the undersides of the leaves retain the color.

These sturdy growers are durable in the landscape and have few pests and diseases. With essential cultural growing requirements met, they’re long-lived garden performers.

H. aspera blooms on old wood (the previous year’s growth). After flowering, they set their buds for the next season in late summer and early fall. In cold climates, this exposes young buds to potential winter damage and subsequent loss of flowering in the following seasons. Rough-leaved selections are hardy in USDA zones 7 through 9.

Native Area

Like many hydrangeas, rough-leaved species are native to Asia. They grow in forested mountain valleys and hillsides of India, Nepal, Taiwan, and southern China.

Planting

Fall and spring are the best times to plant these robust shrubs. The mild conditions pose the least stress on new plants as they become established in the garden. For fall additions, don’t add fertilizer at planting time. Deciduous plants enter winter dormancy to conserve energy, and fertilizer counters this by encouraging new growth. Wait until spring to fertilize for the growing season.

When planting, dig a hole roughly twice the size of the nursery pot. Gently loosen any tightly packed roots and place the plant in the hole. Shrubs benefit from a level crown rather than being planted too high or too low for the best growth and flowering. Ensure the crown (where the base of the stems meets the roots) is at the soil level. Water new transplants thoroughly at the plant’s base.

Transplanting

If you need to move a hydrangea to another garden location, it’s best to do so when plants are dormant. Late fall and late winter/early spring are optimal. Dig a wide berth and go deep around established plants to lift as many roots as possible for transplanting. Water deeply after installing the hydrangea in its new spot.

How to Grow

These are carefree, unfussy plants with low maintenance requirements. However, they have certain cultural conditions that promote overall health and sustainability.

Light

H. aspera grows best in partial shade. Morning sun with afternoon shade protection is ideal in most planting areas.

In cooler climates, the bloomers grow best in more sun as long as soil moisture is consistent. In hot, southern climates (zones 8 and 9), two to three hours of morning sun or dappled sunlight is sufficient. Plants thrive with more shade as heat and sun intensity increase.

Direct afternoon sun scorches leaves and flowers. Provide shade or canopy cover to protect plants from midday sun.

Water

The genus Hydrangea comes from the Greek word “hydor,” which means water. Hydrangeas require ample moisture to thrive. Once established, they tolerate dry spells but grow and flower best with consistent water.

About one inch of water per week is sufficient, with more needed during dry periods. Water until frost to prepare hydrangeas for winter dormancy.

Even moisture ensures the plant’s overall health and vigor, but too much water and saturated soils lead to a decline in flowering and fungal issues. To check the soil’s moisture, the best test is to touch the soil and feel one to two inches below the surface. Wet soil means to hold off on watering, and dry signals time to water.

Water hydrangeas in the morning to retain the most moisture before evaporation. Watering deeply, rather than frequently and shallowly, is best for root growth and moisture uptake.

Watering at the plant’s base avoids splashing the leaves and is best for preventing the spread of fungal and bacterial diseases. Drip irrigation, soaker hoses, or direct hand watering accomplish this. If using spray heads or overhead irrigation, water early in the day so plants have a chance to dry out.

Soil

These summer beauties prefer organically rich, well-draining soils with medium moisture. H. aspera adapts to various soil types, including sandy and clay soils, as long as they’re well-draining and moist. Slightly acidic soils are ideal. Bloom color is unchanged by soil alkalinity.

Amend with composted organic material to improve soil structure in poor soils like clay and sand. Organic matter increases aeration, retains moisture, promotes drainage, and adds nutrition. Spread a generous three- to six-inch layer over the entire planting area.

Temperature and Humidity

Rough-leaved selections tolerate a range of summer and winter temperatures within zones 7-9. These aren’t the most cold-hardy of the species. Buds on old wood are susceptible to damage in winter extremes, resulting in less flowering in spring.

To prepare hydrangeas for winter, add a three-inch layer of mulch for insulation. Compost, pine bark, straw, and leaf litter work well.

Given plenty of air circulation, they thrive in regions with heat and humidity. Soils need to be moist but not overly wet. Hydrangeas may wilt in the afternoon heat, even with moist soil, but they’ll revive in cooler evening temperatures.

Fertilizing

Hydrangeas benefit from compost amendments at planting and each fall or spring. You may opt for a spring fertilizer application to support the heavy bloomers. Look for an organic granular slow-release high in phosphorous, like 10-30-10, to promote growth and flowering.

Avoid overfertilizing, as too much nitrogen produces leafy growth with less flowering. Stop fertilizing in the fall as plants stop actively growing and prepare for winter dormancy.

Maintenance

Asperas generally don’t need pruning for shape. If you choose to prune, do so right after plants finish flowering. Cut stems back to a healthy leaf node. Prune out dead, weak, or winter-damaged stems in late winter or early spring. Avoid pruning in the fall to retain old wood buds.

As regular maintenance, keep plants mulched with a healthy three-inch layer of pine bark, compost, pine needles, or leaves.

Propagation

These woody growers propagate best through stem cuttings and layering. Take softwood cuttings throughout the summer from fresh growth.

Cuttings

Here are simple steps for best practices in taking H. aspera cuttings:

• Cut a four-to-six-inch piece of healthy stem from new growth.
• Remove the foliage from the bottom section of the cutting, keeping one to two upper leaves intact. If the leaves are large, cut half of them off. Keep the cuttings moist until ready to pot.
• Optional: moisten the cutting and generously coat the lower stem with rooting hormone. Tap off any excess rooting powder.
• Plant the cutting in at least two inches of moist, well-draining potting mix. One-half to two-thirds of the stem should be covered, including at least two leaf nodes.
• Place the pot or tray in a bright, warm location, away from direct sunlight.
• Mist or water as needed to keep the soil evenly moist.
• When the cutting resists a gentle tug – generally two to four weeks for hydrangeas – roots are in place, and cuttings are ready to be repotted.
• Plant the cuttings in four- to six-inch pots and move them outside in mild conditions. The new plants will be tender.

Ground Layering

Mound or ground layering is an easy method of propagation that uses existing branching. Choose a low-growing branch and dig a trench beneath it. Scuff a portion of the stem and lay it in the trench, exposing the leafy end of the branch. Cover the stem and weigh it down with a stone or brick. Cut the branch from the mother plant after new roots develop on the stem. Transplant in the garden or into a container.

Popular Varieties

Several beautiful rough-leaved selections are in cultivation. These are exceptional additions to your hydrangea collection. They’re hardy in both flower and foliage.

‘Macrophylla’

‘Macrophylla’ welcomes the heat of summer with mauve-blue blooms ringed in white flowers with purple dot centers. Plants have long, broad leaves and a loose, upright habit.

‘Macrophylla’ is a recipient of the Royal Horticulture Society’s Award of Garden Merit. They reach five to eight feet tall with interest from spring through fall.

‘Burgundy Bliss’

‘Burgundy Bliss’ brings pinky-mauve fertile flowers surrounded by light pink outer blooms. New leaves emerge rich red-purple and mature to green. The undersides of the leaves retain their handsome purple tones.

‘Burgundy Bliss’ reaches six to eight feet tall and wide. The bright blooms appear in July through August on deep, purple-brown stems.

‘Sargent’

Hydrangea aspera subsp. sargentiana cools the summer display with rich lacecaps in deep violet-blue with white ray florets. It has an open habit with lush, velvety leaves.

The branches have peeling bark that adds contrast and seasonal interest. The plants grow five to ten feet tall and are hardy in zones 7-8.

Common Problems

Though aphids are occasional visitors, these sturdy shrubs are free of most pests and diseases. Fungal infections like leaf spot and powdery mildew are sometimes problems. The best prevention is ensuring proper cultural conditions through even watering, partial shade, good air circulation, and healthy soils.

Pests

The best way to control insects is through early detection. Aphids are common sap-sucking garden insects that feed on a variety of plants. They don’t often pose a severe threat, but they can cause stress and leave behind a sticky honeydew that can lead to black, sooty mold. They also spread diseases. 

If you notice curled leaves, stunted growth, or signs of the insect itself, spray plants with a stream of water early in the day to knock them off the stems and deter further damage. A simple horticultural soap or neem oil treats infestations.

Diseases

As with pests, the best disease control is prevention through cultural conditions. Common fungal diseases may be an issue. Water fluctuations and hot, humid conditions foster fungal spores.

Cercospora leaf spot is a fungal disease commonly affecting various hydrangea types. Brown dots on leaf surfaces indicate it, and rainfall and overhead watering promote the spread. Cercospora rarely kills an established hydrangea, though heavily impacted plants may show less blooming and vigor.

To prevent the spread of Cercospora, remove affected leaves and any fallen leaves from the plant during the growing season.

Powdery mildew is another common fungal disease that impacts these selections. A gray-white powdery substance appears on leaves, stems, and buds, which may distort and drop.

Remove affected plant parts and any dropped leaves. Horticultural oils like neem can prevent the spread of this disease to healthy plant tissue early on (but these impact beneficial insects, so be sure to follow application requirements).

H. aspera may experience bacterial wilt, especially in hot conditions after heavy rains or prolonged moisture. Infection begins with bacterial leaf spots, followed by treatment by removing impacted plant parts. It may spread to cause wilt and root rot, for which no remedy exists. Remove the plant for disposal.

Frequently Asked Questions