Bigleaf Hydrangea (Hydrangea macrophylla)

Bigleaf Hydrangea, French Hydrangea, Hortensia, Lacecap Hydrangea, Mop-head Hydrangea, Snowball Plant

Hydrangeas are one of the most common garden shrubs. Within their species, Hydrangea Macrophylla is one of the most popular types that gardeners decide to plant. In this article, we walk through everything you need to know about this type of hydrangea and their care.

I. Appearance and Characteristics 

Hydrangea macrophylla is a species of flowering plant in the family Hydrangeaceae, native to China. It is a deciduous shrub growing to 2 m (7 ft) tall by 2.5 m (8 ft) broad with large heads of pink or blue flowers in summer and autumn. Common names include bigleaf hydrangea, French hydrangea, lacecap hydrangea, mophead hydrangea, and hortensia. It is widely cultivated in many parts of the world in many climates. It is not to be confused with H. aspera ‘Macrophylla’.

The term macrophylla means large- or long-leaved. The opposite leaves can grow to 15 cm (6 in) in length. They are simple, membranous, orbicular to elliptic and acuminate. They are generally serrated.

The inflorescence of Hydrangea macrophylla is a corymb, with all flowers placed in a plane or hemisphere, or even a whole sphere in cultivated forms. Two distinct types of flowers can be identified: central, non-ornamental, pentamerous ones, and peripheral, ornamental, tetramerous ones. The latter have sterile pistils with fertile stamen. The four sepals of decorative flowers have colors ranging from pale pink to red fuchsia purple to blue. The non-decorative flowers have five small greenish sepals and five small petals. Flowering begins in early summer and lasts until early winter. The fruit is a subglobose capsule.

Hydrangea macrophylla blooms can be blue, red, pink, light purple, or dark purple. The color is affected by soil pH. An acidic soil (pH below 7) will usually produce flower color closer to blue, whereas an alkaline soil (pH above 7) will produce flowers more pink.This is caused by a color change of the flower pigments in the presence of aluminium ions which can be taken up into hyperaccumulating plants. Scientists do not understand why this happens, whether it is due to predation or to attract pollinators.

II. How to Grow and Care

Sunlight

Bigleaf hydrangeas thrive when they are planted in partial shade. They can take up to 4-6 hours of sunlight. Morning sunlight is recommended, as afternoon sun can damage the plant when temperatures start heating up.

When they get too much sun, you risk their leaves drying out and turning brown. If they get too much shade you will likely have small flowers and leggy branches as they will be reaching for any sunlight that may be nearby.

Temperature

Bigleaf hydrangeas are hardy in zones 3-7. You can grow them in warmer climates, you just need to take special care that you plant them in the shade so they do not lose too much water and begin to struggle.

Due to the size of these leaves, it is easy for wind to wick the water right out of the surface of the plant. Keeping Hydrangea macrophylla in the shade and protected from the wind is the best way for your shrubs to thrive in warmer climates.

Watering

Bigleaf hydrangeas require about one inch of water per week. Always water at the base of the plant to prevent any fungal infections on the leaves.

In the heat of the summer keep your eyes on the leaves. If they are wilting down towards the ground, they likely need to be watered. If you have planted your hydrangeas in containers, you will probably need to water your plants more frequently than you need to water those that are planted in the ground.

Soil

This species is happiest when grown in well draining soil that has the ability to be kept moist, but not too wet. If your soil is too sandy, or too dense and does not hold the right amount of moisture, you can amend your soil with compost.

The addition of compost will change the structure of your soil, as well as add helpful nutrients. You can mix compost into your garden soil as you plant, or you can add it to the surface of the soil in the same way you would add mulch to your garden. This is a slower way to change your soil structure, but it does work.

Fertilizing

Hydrangeas don’t need fertilized often. However they can benefit from a spring and fall fertilization. If you can find a hydrangea specific fertilizer, or acid-loving plant fertilizer, that would be best, but a basic all purpose fertilizer would work well.

Whether you decide to fertilize or not, is up to you and your soil. If you do choose to provide a fall fertilizer, be sure to apply it before the end of September. If you feed them too late it will promote new growth, and that new growth could be susceptible to frost damage.

Planting Instructions

First, you’ll need to find the perfect planting location. Look for an area in your garden that has good well-draining soil and is located in partial sun.

This spot should also be large enough for the full size of the plant. They may be small now, but planting a large shrub in a tight spot will only cause a headache for you down the road.

Water while it is still in the pot, and get digging. This hole should be about twice as wide and as deep as the pot. The goal here is to make sure that the plant has enough wiggle room to spread out its roots and establish itself. Backfill your plant with your garden soil, and give it a good watering, and continue to check the moisture level until the plant is established.

Pruning

Bigleaf hydrangeas do not need to be pruned frequently due to their nice size and shape. But every plant needs to be pruned every now and again. They produce flower blooms on old wood. Even the new reblooming varieties will have some buds that form on old wood.

What does this mean? Shortly after they finish blooming they will start to produce new flower buds for the next year. If you prune too late you will chop those buds right off and you will end up with very few or no flowers.

In fall when they have finished blooming begin by snipping off the dried and spent flowers. This will help you get a good look at the overall shape of the shrub. Simply trim at the base of the flower. Save those flowers if you think you might want to display them indoors.

Now you can begin by removing any deadwood stems. These stems may be hollow, but will generally just be older looking and oftentimes are easy to remove by hand. I would only take two or three of these out a year. Removing the dead wood increases airflow and creates space for new growth.

Before you begin the pruning process check the stems to make sure there are not any buds formed. Once you have made sure you are in the clear, you can begin to cut the branches. Don’t cut more than one third of the branches to make sure the plant does not go into shock.

Propagation

Bigleaf hydrangeas are very easy to propagate from home. You can take cuttings off of a stem with a few leaves on it. Dip the cutting into rooting hormone and place the cutting into some growing material

You can also lay a ground layer around them. Layering takes place right in your garden and does not require much in terms of supplies. Choose a branch that is close to the ground, and scrape the surface of the branch off to expose fresh plant tissues. Dig a hole a few inches deep, and lay the branch in the hole. Cover the hole with soil, and place a brick or stone from your garden on top.

Whichever method of propagation you choose you will just need to be patient and wait for your cuttings to produce roots. Once this has happened, and the weather is ready for planting you can go ahead and cut the new plant from the mother plant or transplant your rooted cuttings.

Pests and Diseases

Common Pests

You typically will not have too many issues with pests on your bigleaf hydrangeas, they are pretty resilient and tough plants. However, they can be impacted by your typical garden pests such as aphids and beetles, and sometimes deer or rabbits.

You can spray aphids off of your shrubs with the water from your hose, while japanese beetles can be knocked into a bucket filled with soapy water with your hand. If you prefer to use another method you could try an insecticidal soap which is available at your local garden centers. Be sure to read the label instructions!

Common Diseases

Hydrangeas as a whole do not have much difficulty with diseases. However, the fact that they love shade and require a good amount of water ups their chances of having to deal with fungal diseases. This could be anything from leaf spot, to powdery mildew to root rot.

The best way to keep these yucky diseases out of your garden is to keep it clean. Leaves that could have been infected and left to lay in your garden will continue to spread the disease. Watering at the base will also help to keep the leaves dry and create a less than ideal home for fungal spores.

Adjusting Their Color

One of the most fun parts about owning bigleaf hydrangeas is that you can change the color of your flowers by amending the pH of your soil.

If you have acidic soil, 5.5 or below, your plant will produce bluer flowers because your soil will allow the plant to absorb more aluminum. If your soil is sweeter, 6.5 or above, they will have more pink flowers. Not sure what pH your soil is? Then it’s time to get a soil test or a pH test before adding anything into your soil.

If you are looking to acidify your soil you can look for aluminum sulfate at your garden center, and apply in April and May. For soil sweetening, just add some garden lime. Apply the garden lime in April and again in October.

If the variety you’ve chosen is meant to bear white flowers, the blooms will always be white no matter what your soil pH is.

Maintenance

As far as day-to-day or even season-to-season maintenance goes bigleaf hydrangeas don’t need too much. Keeping your gardens free of weeds and other fallen plant debris is a great way to prevent diseases and insect infestations.

As the beautiful blooms begin to fade you may opt to deadhead the blossoms. Unlike annuals, this will not promote more blossoms in the same season but it will neaten up your plant. You could choose to leave the dried flowers on your shrub for added winter interest, or you may choose to let them dry on your plant and use them in your indoor arrangements.

III. Uses and Benefits 

  • Ornamental uses

In climates where Hydrangea macrophylla flowers, place in a mixed shrub border or at the back of a flower bed. Its rich foliage and large size make it a wonderful background for white or light colored flowers, even tall growing perennials and annuals. In warm climates H. macrophylla is good for adding a splash of early summer color to shady areas and woodland gardens. Minimal pruning is recommended for most prolific flowering. Flowers are easily air dried and are long lasting.

While Hydrangea macrophylla is not considered a particularly difficult plant to grow, it may fail to flower. This may be due to cold winter damage to the flower buds, not getting enough sunlight, too much nitrogen fertilizer, or pruning at the wrong time of year. H. macrophylla forms flower buds in late summer. As a result, pruning in late summer, fall or winter could remove potential flowers.

  • Other uses

Amacha is a Japanese beverage made from fermented leaves of Hydrangea macrophylla var. thunbergii.

Hydrangeae Dulcis Folium is a drug made from the fermented and dried leaves of H. macrophylla var. thunbergii with possible antiallergic and antimicrobial properties. It also has a hepatoprotective activity by suppression of D-galactosamine-induced liver injury in vitro and in vivo.

Hydrangea macrophylla is included in the Tasmanian Fire Service’s list of low flammability plants, indicating that it is suitable for growing within a building protection zone.

Leaf extracts of Hydrangea macrophylla are being investigated as a possible source of new chemical compounds with antimalarial activity. Hydrangeic acid from the leaves is being investigated as a possible anti-diabetic drug as it significantly lowered blood glucose, triglyceride, and free fatty acid levels in laboratory animals.

Bigleaf Hydrangea (Hydrangea macrophylla) Details

Common name Bigleaf Hydrangea, French Hydrangea, Hortensia, Lacecap Hydrangea, Mop-head Hydrangea, Snowball Plant
Botanical name Hydrangea macrophylla
Plant type Perennial
Hardiness zone 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b, 10a, 10b, 11a, 11b
Growth rate Fast
Harvest time Fall
Height 3 ft. 0 in. - 6 ft. 0 in.
Width 3 ft. 0 in. - 6 ft. 0 in.
Sunlight Dappled Sunlight (Shade through upper canopy all day)
Soil condition Clay
Flower color Blue
Leaf color Gold/Yellow