Hydrangea macrophylla in pot

Credit: Maja Dumat

Green foliage Hydrangea macrohpylla

Credit: Mauro Halpern

Hydrangea violet in pot

Credit: David J. Stang

Pink hydrangea Hydragnea macrophylla

Credit: Raulbot

Hydrangea macrophylla, large-leaf hydrangea

Hydrangea macrophylla, better known as hydrangea, comes to us from Japan and Korea. In the Japanese archipelago, this plant symbolizes inconsistency, and its blossoming heralds the arrival of the rainy season. At our latitudes, its flowers are a sign that fine weather has returned.

How to recognize the hydrangea, Hydrangea macrophylla?

Hydrangea macrophylla is an upright, rounded shrub. It reaches a maximum height of two meters in all directions.

The short, woody, branched stem is covered with gray or ochre bark.

The oval leaves have toothed margins. The green blades measure up to 20 centimetres long.

Hydrangea macrophylla flowers in summer. In some regions, flowering lasts until late autumn. The shrub is then adorned with rounded or conical bunches of flowers. The inflorescence comprises two types of flowers: decorative florets and non-decorative florets. Decorative florets are the most visible. Their flowers are formed by four colored petals. The non-decorative florets are located in the center or below the decorative ones. They measure just a few centimetres and consist of five sepals, five tepals and a dozen stamens.

In the botanical variety, flower color depends on soil composition. Blue hydrangeas thrive in acidic, aluminum-rich soils. Pink or white Hydrangeas bloom in alkaline or neutral soils. Some cultivars, however, guarantee you the same flowering every time. These include madame Émile Mouillère' Hydrangea with its white flowers, and hydrangea 'Endless Summer 'Summer Crush', with its red flowers.

After flowering, the big-leaf hydrangea produces a fruit, a globular capsule about 60 cm long. It contains the seeds.

Hydrangea macrophylla is toxic. The plant can cause allergic skin reactions in humans. But hydrangea is most dangerous to animals. Dogs, cats, rabbits and birds are highly sensitive. Ingestion of the leaves or flowers causes vomiting and digestive problems. In severe cases, it can also lead to cardiac and nervous disorders.

Our maintenance tips

The color of your Hydrangea depends largely on the pH of your soil. In acid soil, flowers are blue. In alkaline soil, flowers are pink or white.

Watering

Hydrangea macrophylla can withstand neither drought nor excess water.

Before watering, check the condition of the potting soil. The surface must be at least one centimeter dry.

Repotting

Obtain a perforated pot twice the size of the root ball. Fill it with a mixture of equal parts heather and garden soil.

Plant your Hydrangea in the center. Add potting soil, but do not fill the pot completely. Stop a few centimetres from the edge to form a watering basin. Press down and water generously.

Flowers are heavy and can bend branches. You can stake them to take the strain off the plant and keep it upright.

Fertilization

You can stimulate the growth of your plant during its growth phase, in spring and summer, with fertilizer.

Fertilize with a fertilizer for acid-loving plants. You can choose a hydrangea or bougainvillea fertilizer, for example.

Prune

Hydrangea macrophylla bloom on the previous year's wood. You mustn't prune too much, otherwise your plant won't flower.

Remove wilted flowers. Also remove frozen or broken branches.

Prune branches one to two centimetres above the last buds. Use a clean, sharp instrument to promote healing.

If your Hydrangea is old, cut back a few old branches by half to encourage new growth. But don't do it to all the branches! You won't have any flowers for a year!

Plantation

Once the last spring frosts have passed, you can plant.

Plant your Hydrangea in semi-shade, along a wall or under a tree to protect it from direct sun, frost and wind.

Soak the rootball of your Hydrangea, still in its container. Preferably use rainwater. Tap water is often too hard.

Meanwhile, dig a hole 1.5 times deeper than the root ball and three times as big. Place a little compost at the bottom.

Plant your Hydrangea macrophylla. The collar should reach ground level. Fill the hole with a mixture of heather soil (50%) and garden soil (50%).

Mulch the soilwith organic matter such as dead leaves or pine bark. Water copiously to encourage rooting.

You can also stake the flowers if their weight causes the stems to bend.

Cutting

Select a branch that has not yet flowered and whose tip is still flexible.

Take a section about ten centimetres long. Cut with clean, sharp pruning shears below a node.

Dress your cutting. Remove the leaves on the lower half of the shoot. You can reduce the size of the others by half.

Fill a pierced pot with a mixture of universal potting soil(1/3), sand(1/3) and heather (1/3). You can also use potting soil for seedlings and cuttings mixed with perlite. Form a pre-hole and plant your cutting in the center. Pack lightly.

Cutting is done in a smothered fashion. Place your Hydrangea in a mini greenhouse or translucent crate. You can also cover it with a transparent plastic bag.

Your cutting needs humidity to develop. Fog the leaves and potting soil whenthey are dry, to maintain a high level of humidity. But beware of rot! You need to aerate for a few minutes every day to avoid rot.

Diseases / Threats

Powdery mildew

Mealybugs

Information

Family	Hydrangeaceae - Hydrangeaceae
Type	Hydrangea - Hydrangea
Species	Large-leaf hydrangea - Hydrangea macrophylla
Lifecycle	Perennial
Foliage	Deciduous
Exposure	Half-shade
Substrats	Humus soil Sandy soil
Planting methods	Open ground In pots In tubs
Categories	Shrub Flowery
Tags	Beginner Flowery Rustic Toxic
Origin	Southeast Asia
Hardiness (USDA)	7a
Leaf color
Flower colors