How to Grow Hydrangeas

Hydrangeas are grown mainly for their showy flower heads. Hydrangeas are divided into two groups: lace caps and mopheads. Lacecaps have flattened flowerheads with small flowers in the center surrounded by larger flowers around the perimeter. Mopheads have nearly spherical flower heads. Flowers of both can be white, pink, red, lavender, and blue.

Hydrangeas are deciduous shrubs native to Asia and North and South America. They belong to the Saxifrage family.

Hydrangeas thrive best in rich moist soil and flower freely in an open situation but will grow under varying conditions. Rather severe pruning should be practiced and the weak growth thinned to encourage strong shoots for good flower heads.

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Blue hydrangeas are very popular and sometimes a seeming miracle takes place when plants propagated from the blue variety produce pink flowers. This is due to the change in soil acidity. Blue flowers are produced in acid soil. Hence growers of pot plants often add iron to the soil or water with a solution of alum at the rate of a teaspoonful to one gallon of water, or with aluminum sulfate–3 ounces to the gallon.

Outdoors a sandy soil and the addition of peat moss, leaf mold, or any other acid-creating material will aid in keeping blue varieties blue.

Good plants can be grown in one year from cuttings. Young plants can be set outdoors in pots for summer or planted in a sunny place then lifted and potted in fall. Older plants may be cut back and planted out for another season of flowering and either protected outside or lifted and stored in a frost-proof place.

Choosing the Right Hydrangea

There are several types of hydrangeas, and selecting the right one for your garden depends on your climate, available space, and desired aesthetic. Common types include:

Hydrangea macrophylla (Bigleaf hydrangea): Known for its large, ball-shaped blooms, which can be pink, blue, or purple depending on the soil pH.
Hydrangea paniculata (Panicle hydrangea): Features cone-shaped flowers that start white and may turn pink with age. Tolerates full sun better.
Hydrangea arborescens (Smooth hydrangea): Produces large, round white or pink blooms. ‘Annabelle’ is a well-known variety.
Hydrangea quercifolia (Oakleaf hydrangea): Has distinctive lobed leaves and white flowers that fade to pink, with stunning autumn foliage.
Hydrangea serrata (Mountain hydrangea): A more compact shrub with lacecap blooms.

Planting Hydrangeas Quick Tips

Timing: The best time to plant hydrangeas is in spring or fall when the weather is cool and mild.
Location: Hydrangeas prefer partial shade. They thrive in morning sun with afternoon shade, although panicle hydrangeas can tolerate more sun.
Soil: Hydrangeas prefer moist, well-draining soil rich in organic matter. For Bigleaf hydrangeas, the soil pH affects bloom color—acidic soil (pH below 6) yields blue flowers, while alkaline soil (pH above 7) produces pink flowers.
Planting:
1. Dig a hole that is about twice the width of the root ball but no deeper than the root ball itself.
2. Place the hydrangea in the hole, making sure the top of the root ball is level with the ground.
3. Backfill the hole with soil, tamping it down gently to remove air pockets.
4. Water thoroughly after planting to help the plant settle in.

Caring for Hydrangeas Quick Tips

Watering: Hydrangeas need consistent moisture, especially in hot weather. Water deeply 1–2 times per week to encourage deep roots.
Mulching: Apply a layer of organic mulch around the base of the plant to retain moisture, regulate soil temperature, and suppress weeds.
Fertilizing: Hydrangeas benefit from a balanced, slow-release fertilizer applied in early spring. Avoid over-fertilizing, as too much nitrogen can result in lush foliage with fewer blooms.

Pruning Hydrangeas

Bigleaf and Mountain Hydrangeas: These types bloom on old wood (last year’s growth). Prune them after flowering, typically in late summer, by removing spent flowers and weak or dead stems.
Panicle and Smooth Hydrangeas: These bloom on new wood (current season’s growth), so they can be pruned in late winter or early spring. Cut back up to one-third of the plant to encourage healthy new growth.
Oakleaf Hydrangeas: Prune after flowering, focusing on dead or damaged branches and lightly shaping the plant.

Using Hydrangeas in the Garden

Hydrangeas are versatile and can be used in various ways to enhance your garden’s aesthetic:

Flower Beds and Borders

Hydrangeas make excellent centerpiece shrubs in mixed flower beds or borders. Their large blooms and bold foliage add texture and color throughout the growing season.
Pair them with perennials like hostas, astilbes, or ferns to create a lush, layered look.

Foundation Plantings

Plant hydrangeas along the foundation of your home to add height and soften the lines of the building. Their large size and dense foliage work well for this purpose.
Choose varieties based on the available space—compact hydrangeas are best for smaller areas, while larger varieties can fill wider spaces.

Hedging and Screening

Hydrangeas can be used as informal hedges or screens. Oakleaf and panicle hydrangeas, in particular, work well for this purpose due to their size and upright growth habit.
Plant hydrangeas in a row for a colorful hedge that provides privacy and visual interest during the growing season.

Container Gardening

Compact hydrangea varieties, such as dwarf Bigleaf or Mountain hydrangeas, are perfect for containers on patios, decks, or balconies.
Ensure containers have good drainage and use high-quality potting soil. Water frequently, as container-grown hydrangeas can dry out more quickly.

Cut Flowers

Hydrangeas are excellent for cut flower arrangements due to their large, showy blooms. Panicle and Bigleaf varieties are especially popular for floral displays.
To dry hydrangea flowers for arrangements, cut them in late summer when blooms have matured. Hang them upside down in a cool, dry place.

Changing Hydrangea Bloom Color

For Bigleaf and Mountain hydrangeas, you can change the flower color by adjusting the soil pH.
- To make flowers blue, increase soil acidity by adding aluminum sulfate or sulfur.
- To turn them pink, raise the soil’s alkalinity by adding lime.
This process takes time, so start a season in advance for desired results.

Get to Know Hydrangeas

Plant type: Deciduous summer- or fall-blooming shrub
Growing Zones and range: 4-9, more below
Hardiness: Half-hardy
Height and width: 6 to 15 feet (1.8-4.5m) tall, 3 to 8 feet (1-2.4m) wide depending on the variety
Foliage: Broad to narrow ovate or lance-shaped, toothed opposite or whorled leaves
Flowers: Two forms: (1) lacecaps have flattened flowerheads with small flowers in the center surrounded by larger flowers around the perimeter; (2) mopheads have nearly spherical flower heads. Flowers of both can be white, pink, red, lavender, and blue.
Bloom time: Summer
Uses: Thrives in shade; specimen plants, plantings, shrub border, or in containers; climbers can be used to clothe a shaded wall or fence or grow up tree trunks
Garden companions: For white-flowering hydrangeas, ‘Royal-Purple’ smoke bush (Cotinus coggyria ‘Royal Purple’); Shubert chokeberry (P. virginiana ‘Shubert’)
Common name: Hydrangea
Botanical name: Hydrangea spp.
Family: Hydrabgeaceae
Origin: North and South America, East Asia

Where to Plant Hydrangeas

Plant hydrangeas in full sun but protect plants from hot afternoon sun; plant in partial shade in hot summer regions
Grow hydrangea in humus-rich, well-drained soil, preferably acidic

When to Plant Hydrangeas

Set outdoors during fall or spring. Keep well-watered during summer.

Planting and Spacing Hydrangeas

Space hydrangeas 3 to 8 feet apart depending on the variety,

How to Water and Feed Hydrangeas

Hydrangeas need ample water; keep the soil evenly moist.
Fertilize hydrangeas with an all-purpose fertilizer in spring and again at midsummer.

Hydrangea Care Through the Year

Mulch around hydrangeas with aged compost to protect the roots and feed the soil.
Hydrangea will flower without pruning but will flower better in flowers that are cut back in fall to a strong, flat flower bud and weak. Cut old, weak stems to the ground in the fall.
Prune Hydrangeas to control size and form.

How to Grow Hydrangea as a Houseplant

Hydrangea macrophylla can be grown as a houseplant.
Place hydrangea in a room where the temperature is average, humidity is average to high, and light is direct.
The medium should be soilless and kept evenly moist at all times.
Store-bought plants do not need to be fertilized.
After the flowers have faded, plants may be moved into the garden.
If you want to force a hydrangea into bloom, the plant should be potted in the fall and placed outdoors in a dark cold frame for si week to induce flower buds before being moved indoors.
The temperature must drop below 40°F (4.4°C) for flower buds to form.
Tall plants may need to be staked.
The flower color of hydrangeas can be changed by manipulating the pH; blue flowers require an acidic medium; pink flowers require an alkaline medium.

Hydrangea Pests and Diseases

Hydrangeas are susceptible to attacks by slugs.
Gray mold, powdery mildew, rust, ringspot virus, and leaf spots are also common.

Hydrangea Propagation

Sow Hydrangea seeds in containers in a cold frame in spring.
Hydrangea macrophylla take cuttings anytime during the growing season.
Hydrangea paniculate take cuttings in summer.
Hydrangea quercifolia layer in spring or soil in fall.

Hydrangea Varieties to Grow

H. arborescens, Wild or smooth hydrangea, rounded, deciduous shrub with long-stalked, broadly ovate leaves, to 7 inches (18cm) long, dark green above and paler beneath. Domes or flattened corymbs, to 6 inches (15cm) across, of crowded, dull-white, mainly fertile flowers are borne in summer. To 3-5 feet (1-1.7m) tall and wide. Eastern United States. Zones 5 to 9. Hydrangea arborescens blooms on the current year’s growth, so prune hard to the ground each spring; best in Zones 6-9.
H. aspera, is an upright, deciduous shrub with large, lance-shaped to narrowly ovate, dark green leaves, to 10 inches (25cm) long, downy beneath. From late summer to autumn, bears flattened corymbs, to 10 inches (25cm) across, of blue to purple fertile flowers, surrounded by white, sometimes pink- to light purple sterile flowers. To 10 feet (3m) tall and wide. East Asia.
H. involucrata, a spreading, deciduous shrub with broadly ovate-oblong, bristly, dark green leaves, to 6 inches (15cm) long. In late summer, bears domed corymbs, to 5 inches (13cm) across, of small, blue fertile flowers, surrounded by white to pale blue or pink sterile flowers. To 3 feet (1m) tall and 6 feet (2m) wide. Japan, Taiwan.
H. macrophylla, bigleaf hydrangea, grows 2 to 10 feet tall in Zones 6-9; it has broad, thick leaves; it has blue or pink flowers (blue in acid soils, pink in alkaline); flowers are large, flat clusters up to 10 inches across; cultivar ‘Nikko Blue’ will bloom blue; ‘Mariesii’ bears pink flowers; all best in Zones 4-8.
H. paniculata grows to 20 feet tall and 10 feet wide; has elliptical dark green leaves; has white flowers in large pyramidal clusters in midsummer to early fall; ‘Grandiflora’ has white, snow-ball-like flowers.
H. petiolaris, Climbing hydrangea, vigorous, woody, deciduous climber, clinging by aerial roots. Ovate-rounded leaves, to 4.5 inches (11cm) long, have heart-shaped bases and are dark green, sometimes turning yellow in autumn. In summer, bears domed corymbs, to 10 inches (25cm) across, of white fertile and sterile flowers. To 50 feet (5m) tall. Russia (Sakhalin), Korea, Taiwan, and Japan.
H. quercifolia grows to 10 feet tall and wide; has oak-shaped leaves; has white flowers that are borne in erect, pyramidal clusters in early to late summer; best in Zones 5-8.
H. sargentiana, an upright, deciduous shrub with thick, bristly shoots and large, broadly ovate, very bristly, dark green leaves, to 10 inches (25cm) long. Flattened corymbs, to 9 inches (23cm) across, of blue to purple fertile flowers, surrounded by white sterile flowers, sometimes tinged purple, are produced from late summer to autumn. To 10 feet (3m) tall and more and 7-8 feet (2.2-2.5m) wide. China.
H. serrata, Mountain hydrangea, compact, erect, deciduous shrub with narrowly ovate, pointed, mid-green leaves, to 6 inches (15cm) long. Flattened corymbs, 2-4 inches (5-10cm) across, with a few pink or blue sterile flowers and numerous blue or pink fertile flowers, open from summer to autumn. To 4 feet (1.2m) tall and wide. Korea, Japan.
H. serratifolia, a vigorous, woody, evergreen climber, similar to H. seemanii, but with elliptic, leathery, dark green leaves, to 6 inches (15cm) long, sharply toothed on young plants. In summer, clustered, corymb-like flowerheads, to 6 inches (15cm) across, with white fertile flowers and usually no sterile flowers, open from large, spherical buds. To 50 feet (15m) tall. Chile, Argentina.
H. villosa, spreading to erect, deciduous shrub or small tree with lance-shaped to narrowly ovate, velvety, dark green leaves, 3.5-10 inches (9-25cm) long. In late summer, bears flattened corymbs, 6 inches (15cm) across (often more), of blue-purple or rich blue fertile flowers and lilac-white or rose-lilac sterile flowers. To 4-12 feet (1-4m) tall and wide. Tibet, China, Myanmar, and Taiwan.

Hydrangea Frequently Asked

questions

Q: How do I grow hydrangea in the house?

A: Place hydrangea in a room where the temperature is average, humidity is average to high and light is direct. Use a soilless medium and keep it evenly moist at all times. After the flowers have faded, plants may be planted in the garden.

Q: How can I force my hydrangea into blooming?

A: To force a hydrangea into bloom, pot the plants in fall and place them outdoors in a dark cold frame for six weeks to induce flower buds before you move them indoors. The temperature must drop below 40°F for flower buds to form.

Q: How long will a hydrangea flower in the house?

A: Hydrangea should flower not less than 3 weeks. Keep the plant away from a hot, sunny window and forced heat. Water thoroughly twice a day.

Q: What care should be given pot hydrangeas?

A: Florists’ hydrangeas are propagated from cuttings in early spring and grown in 4-inch pots which are sunk in the open ground during the summer. Put the plants in larger pots in autumn and place them in a protected cold frame that is well-ventilated. Bring the plant inside before hard freezing. Give the plant just enough water to prevent dying.

Q: Can my florist hydrangea be planted in the garden after it has stopped flowering?

A: Yes. After it has finished blooming cut back stems about half the length, remove the plant from the pot, and plant it in the garden where it will have plenty of room. Water well. It will grow into a big, shrubby plant.

Q: What makes the hydrangea flower blue or pink?

A: Acidity of soil causes blue flowers, but some varieties come blue more readily than others. Repeated watering with alum solution or aluminum sulfate (1 level teaspoon to 1 gallon of water) will cause blueness. Add 1 tablespoon of alum to the potting mixture to get pink flowers.

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