Hydrangeas: expert tips on planting, fertilising & pruning

This article will provide you with everything you need to know about hydrangeas: from planting and growing to cutting and choosing the right variety.

The Hydrangea genus consists of 70 different species, most of which originate from East Asian regions. All species are woody plants that come in different forms –as small shrubs for example or as climbing plants. Keep on reading to learn more about hydrangeas.

The flowers of the hydrangea are usually arranged in panicles or umbel-like inflorescences. The larger, more visible outer flowers make up the actual ornamental value. The flowers inside the inflorescences contribute to the seed development and are not visible at first glance. In the following we will take a closer look at hydrangeas, different varieties and their care.

Hydrangea species and varieties

The most notable species are deciduous shrubs meaning they bear leaves in summer and cast off their foliage in winter. The biggest star among hydrangeas is the Hydrangea macrophylla which originates from Japan and is also referred to as bigleaf hydrangea. Its characteristic inflorescences are ball-shaped or flat like a plate with less of the large ornamental flowers. Further popular varieties include the panicled hydrangea (Hydrangea paniculata) and the smooth hydrangea (Hydrangea arborescens). For those who want not just stunning flowers but also decorative foliage, the oakleaf hydrangea (Hydrangea quercifolia) is the right choice. Then there is Hydrangea sargentiana, which is known for its velvet soft leaves, as well as climbing hydrangeas (Hydrangea petiolaris) and the tea of heaven hydrangea (Hydrangea serrata).

For more info on different hydrangea varieties of the above-mentioned species click here.

Planting hydrangeas

In the following you will learn about location and soil conditions for hydrangeas including differences when planting in pots compared to garden beds.

Planting hydrangeas in garden beds

Regarding soil hydrangeas have specific requirements. The pH value ideally lies between 4 and 5. Depending on the colour of the flowers you will want to modify accordingly. Lower the pH value for blue and purple hydrangeas, increase for lighter varieties in pink and white. It will not harm your hydrangea if the pH value is slightly more alkaline, but it may lead to deficiency symptoms in the long term and colours might not pop out as desired. Hydrangeas also require sufficient water supply as they quickly show drought damage. Thus, we recommend choosing a location with good water storing capacity. Nevertheless avoid waterlogging to prevent the root from rotting which would mean the subsequent death of the plant.

Once the location is decided on you can start planting. With alkaline soils, it may be a good idea to dig a slightly larger hole. That way, there is room for extra substrate with a suitable pH value, such as rhododendron substrate. Generously water the hydrangea before and after planting. Loosened the soil around the plant to make it easier for the hydrangea to root. It is a common misconception that patting down the earth will hold the plant in place; you are not doing your hydrangea a favour.

Planting hydrangeas in pots

Location requirements are the same for hydrangeas in pots. They will be perfectly happy even in a flower pot especially in semi-shady areas. Potted hydrangeas need to be watered more often. Thus, make sure your pot is big enough. It is also recommended to use rhododendron soil for planting. You can soak your hydrangea in a bucket of water until bubbles stop welling up. That will give it proper water supply right from the beginning. Water again after planting to settle in the loosened substrate and give the roots access to water and nutrients.

Find more details on planting hydrangeas in this article.

On the balcony

Hydrangeas also make beautiful balcony plants. Since they prefer shady locations, east, west or north facing balconies are perfect. If you want to keep your hydrangea on a south-facing balcony, shade it from the sun around midday and make sure it has enough water.

Maintaining hydrangeas

Hydrangeas are reliable flower stunners in the garden – but they do require the right care. From watering to fertilising to pruning; the following paragraph is all about maintenance.

Watering hydrangeas

Hydrangeas are thirsty plants and need regular watering. Especially in hot summers, hydrangeas have to be watered up to several times a day. That also goes for hydrangeas in garden beds. Regular watering will prevent unnecessary drought damage such as dried leaves and flowers.

Fertilising

Every type of hydrangea can develop into a healthy and vigorously flowering beauty with the right fertilisation. For Hydrangea macrophylla fertilisation is also key for the flower colour but to a lesser extent than pH value of the soil.

When planting hydrangeas, a long-term fertiliser is advisable. The slowly released nutrients and the activation of soil life form a good base for establishing the new plant at its location. By the way, hydrangeas are planted either in spring (March – May) or in autumn (October – November). Older hydrangeas are fertilised once a year if they grow in a garden bed and due to the smaller substrate volume twice a year when in a pot. Plantura Hydrangea Food is a great example of a long-term fertiliser. It is based on non-animal materials from the food and beverage industry and animal feeds as well as mineral components, which are also used in organic farming. This will perfectly provide your hydrangea with all important nutrients.

For more info about the influence of substrates and fertilisation on the flower colour and how to achieve the blue colouring on your hydrangeas read this article.

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Pruning

The right cut is indispensable for magnificent flowers. Hydrangeas can be cut either in autumn or spring. In order to determine the right time, you should first know which hydrangea species you are dealing with. Hydrangea macrophylla and Hydrangea quercifolia for example already form their flowers in autumn for the following year meaning they flower on last year’s wood. If you cut back too much, you may lose the beautiful flower. Panicled (Hydrangea paniculata) or smooth hydrangeas (Hydrangea arborescens), on the other hand, bloom on so-called annual wood. Their flowers form the same year they bloom. Thus, these two popular hydrangeas are among the species that can be cut back unharmed.

In this article you can learn more about pruning hydrangeas.

Overwintering hydrangeas

In general, you can rely on the fact that hydrangea species are hardy when offered in stores in temperate climates. Frost damage is still possible though and will affect the flowering of hydrangeas. To avoid this, consider the following:

• Choose a protected place in semi-shade already when planting
• Apply winter protection: leaves, jute sack, fir branches or mulch will protect the plant (always cover the outer shoots close to the ground!)
• Fertilising with mineral nitrogen is a big no-no from mid-July onward; organic fertilisers can be used until August
• Use a fertiliser with high potassium content, as this is essential for frost resistance
• Even as temperature increases , do not remove winter protection completely until mid of May/ the Ice Saints have passed (11^th to 15^th of May); have the jute bag ready for frosty nights; of course, it is possible and important to expose the plant during the first warm weeks
• Hydrangeas in pots require the same protection measures
• In addition, potted hydrangeas should spend the winter in protected garden areas; pots with a diameter of less than 35 centimetres should be kept frost-free (3 – 5 °C) in a shed or a garage for example

Propagating hydrangeas

For the reproduction of hydrangeas, the only thing you need is access to an already existing hydrangea plant. Vegetative propagation produces clones of the beloved hydrangea from your own garden. Basically, hydrangeas can be propagated either by division, layering or cuttings.

Pests and diseases

With good care, hydrangeas are generally not too susceptible to diseases and pests. Nevertheless, even with great care pests and diseases can occur. The most common issues with hydrangeas are the leaves turning yellow due to chlorosis and mealybugs.

Yellow leaves on your hydrangea most likely mean a lack of nutrients and lack of iron in particular. The disease is called chlorosis. Although natural soil contains enough nutrients the hydrangea is not able to absorb them. Remedies for hydrangea iron deficiency are discussed here.

Mealybugs (Pseudococcidae) are a frequent pest on hydrangeas. They are easy to spot due to the white webs that look like white hair or fluff. The mealybugs suck on the plants and absorb the sap, transferring harmful viruses to the plant. The infested leaves turn yellow and eventually fall off. If the mealybug infestation is severe, hydrangeas may even die.

Drying hydrangeas

The impressive flowers of hydrangeas make a great decorative element. Dried hydrangeas will spruce up your house even months after the hydrangea season is over. It is important to deadhead the flowers when fully in blossom and before they wither. Keep in mind that most likely no flowers will grow off of that branch the following year. The lower you cut the shoot, the less likely it will be to flower.

Are hydrangeas bee-friendly?

As mentioned above, the actual flowers that carry the seeds are hidden inside the inflorescence. They bear a moderate supply of pollen and nectar. Unfortunately, the numerous hybrid forms and varieties of hydrangea are often completely uninteresting for pollinators because breeding focuses on the ornamental value of the flowers more than their nourishing potential for insects.

However, you can turn your garden into a paradise for bees with other bee-friendly plants about which you can learn in this article.