How To Grow And Care For French Hydrangeas

Picking out French hydrangea, hydrangea macrophylla, is like ordering iced tea. You're going to have to make a decision: Sweet or unsweet? Mophead or lacecap? There's no right or wrong answer—it's about personal taste. Hydrangea macrophylla, also called bigleaf hydrangeas, have blooms categorized as mopheads or lacecaps. And like iced tea—sweet or unsweet—both are Southern staples.

Mopheads are the most popular. Coveted for their voluptuous blooms, ranging in size from as small as a baseball to bigger than a cantaloupe, they fill the summer border with heavenly shades of blue, pink, purple, and white the way no other flowering shrub can. Because they lose their leaves in winter, it's a good idea to sandwich them between evergreens, such as camellias, and low-growing azaleas or mondo grass. Be mindful of where to plant French hydrangeas, as consumption is toxic to pets and humans.

Plant Attributes

French Hydrangea Care

French hydrangeas, or bigleaf hydrangeas, are categorized as mophead or lacecap. Mophead hydrangeas have big, puffy balls, while lacecaps are flatter, with smaller buds in the center. The "flower heads" are actually inflorescences consisting of tiny, inconspicuous fertile flowers and large, decorative infertile sepals. Mopheads contain mostly large clusters of sepals, while lacecaps contains many tiny flowers among the sepals. Lacecaps may be more subtle but are equally stunning when in bloom. The clusters of flowers are slightly domed and ringed with delicate fertile florets, and they beckon bees and butterflies to the garden. Like mopheads, their flowers float atop broad, bright green, deciduous leaves. While mopheads may be showier, lacecaps are sublimely elegant. Showcase drifts of these ethereal blooms in woodland settings with high shade and combine with sweeps of ferns and hostas. Hydrangeas can become aggressive in some environments but are generally not considered invasive.

Light

Bigleaf hydrangeas thrive in the morning sun and light afternoon shade. If hydrangeas receive too much direct sunlight, these plants will scorch, and the leaves with droopy or turn yellow from overexposure. However, for best blooms, they do need some sunlight.

Soil

French hydrangeas love moist, well-drained soil. These plants thrive when organic matter, such as rotted manure or compost, is amended to the soil to help it retain moisture. Layering organic materials near the base of the shrubs can help protect the plant's growth.

Water

French hydrangeas need a balanced watering schedule, so it is not overwatered or droopy when too dry. The best way to test if your plant needs more water is to ensure the top few inches of soil remain moist. Make sure when watering that it reaches the roots. If you are experiencing drought conditions, provide hydrangeas with a deep watering to ensure the roots stay well hydrated without sitting in water, which can cause root rot. 

Temperature and Humidity

Moderate temperatures are best for French hydrangeas. This plant will need more water in areas that experience hot, humid summer conditions. These plants are typically hardy in zones 6-9, but it depends on the cultivar.

Fertilizer

Organic compost or balanced fertilizers will help hydrangeas grow. Add the fertilizer to French hydrangeas during the spring for best results, as adding organic material in late summer will leave the plant susceptible to winter frost during dormancy.

Additionally, soil pH influences the bloom color of French hydrangeas. Blue flowers occur in acidic soil, while pink flowers appear in alkaline soil. If you're partial to a particular bloom color, amend the soil with aluminum sulfate to acidify the soil or garden lime to produce alkaline soil.

Types of French Hydrangeas

• 'Abracadabra Star': Pink summertime blooms with black stems and shallow roots.
• 'Cityline Paris': Pink-red flowers that are mildew resistant. These plants mature to a green color.
• 'Cityline Vienna': Flowers bloom in blue or pink varieties depending on the acidity in the soil.
• 'Blushing Bride': Pure white flowers with big, round blooms that mature to blush pink.
• 'Lady in Red': Lacecap hydrangea with flowers in a pinkish-white hue in early summer that mature to a rose pink or blue.

Pruning

French hydrangeas that flower once, such as 'Nikko Blue,' bloomed on last year's growth. Prune just after flowering in summer. Repeat-blooming French hydrangeas, such as 'Blushing Bride', flower on both old and new growth—prune these carefully, removing the spent flowers without pruning new buds. Remove older or dead branches back to the group using loppers to keep your hydrangea healthy. Removing old canes and dead blossoms can help promote new growth. You can tell if a branch is finished by using a blade to scratch the top layer of the stem and examine it for signs of green growth, meaning it is still healthy. 

Propagating French Hydrangeas

One way to propagate French hydrangeas is through cuttings. Take cuttings in the spring or winter, depending on your preferences.

1. In spring or early summer, look for new growth branches off the main stem with a few leaf nodes, and use sharp pruners or a knife to cut off a strong, healthy stem tip.
2. Remove leaves on the bottom of the cutting and leave only 2 to 4 leaves, so that the cutting can focus its energy on new growth instead of retaining old growth. 
3. Place cutting in a root hormone solution.
4. Plant cutting in moist, well-drained seed-starting mix in a container with good drainage.
5. Cover with a plastic bag to help retain humidity and keep soil moist.
6. Place container in an area with partial sunlight or under grow lights. 
7. Check soil before watering--don't allow it to dry out, but don't oversaturate the soil.
8. Look for signs of rooting, such as small buds at the end of the stem.
9. Allow the cutting to grow for 6 to 8 months indoors, then harden off for two weeks before planting in the garden.

Potting and Repotting French Hydrangeas

When buying French hydrangeas, look for more than just pretty flowers. Choose a full plant with equal branching on all sides. Fat buds or flower heads should cover the stems that are ready to open—or opening in late spring and early summer. Leaves should be bright green and not drooping (an indicator of infrequent watering).

French hydrangeas love moist, well-drained soil, morning sun, and light afternoon shade. Water as soon as you get them home, saturating the soil in the pot. Before planting, play with the placement. Space most French hydrangeas three to four feet apart, but check the tag to see how wide your selection will grow. Dig a hole two to three times as wide as the pot but at the same depth. Remove the plant from its container, and set it in the center of the hole. Gently loosen the sides of the root ball with your fingers. Fill the hole with a mixture of half the original soil and half compost. Mulch and water regularly to help establish your plant. If you buy a repeat bloomer, it's essential to water, feed, and remove spent blossoms regularly to encourage new flowers.

Overwintering

French hydrangeas only require a little winter maintenance. After blooming ends, protect the shrub by deadheading the flowers. Use mulch to protect the plant's roots during the colder months.

Common Pests & Plant Diseases

French hydrangeas are susceptible to fungal, bacterial, and viral diseases. Some fungal diseases include leaf spots, powdery mildew, and Botrytis blight. Bacterial wilt can occur when hydrangeas grow in areas with hot, humid temperatures and heavy rain, which can also cause root rot. Some pests include aphids, which insecticidal soap can help treat. Unfortunately, deer also love hydrangeas.

Common Problems With French Hydrangeas

French hydrangeas can fail to bloom because of improper pruning time or an imbalance of light, water, or fertilizer. When hydrangea care is mismanaged, these plants are susceptible to various issues.

Leaves Turning Brown

Hydrangea leaves and blooms might turn brown during drought or extreme heat periods. Lack of water, or dry soil conditions, will impact the plant's growth, meaning more frequent watering is needed.

Curling Leaves

Curling leaves indicate over- or under-watering, dry soil conditions, or nutrient deficiency. Other reasons for curling leaves include fungal and insect infections. When disrupted by these conditions, hydrangeas have weakened plant tissues, which causes curling to occur.