Hydrangea serrata: all about planting, care & pruning

Hydrangea serrata (also called ‘tea of heaven’ or ‘mountain hydrangea’) stand out with their umbrella-like flowers. Find out how to plant and care for the plants, with detailed instructions on pruning.

Hydrangea serrata looks a bit wilder and more original next to the lush bigleaf hydrangea. Unlike some of their relatives, whose flowerheads are composed only of false flowers, these hydrangeas also have numerous fertile flowers, making them a valuable source of food for insects in summer.

Hydrangea serrata: flowering period, characteristics and origin

Hydrangea serrata is also known as ‘lacecap hydrangea’, ‘tea of heaven’ and ‘mountain hydrangea’. The plants are native to the mountain forests of Japan. It grows as a spreading half-shrub, reaching a height of up to 1.5 metres. During the flowering period from July to October, the umbrella-shaped flowers that stand together gradually open. In the centre are the rather inconspicuous fertile flowers surrounded by a wreath of false flowers. These are composed of four to five oval petals. The umbrella panicles, about 10 cm in size, shine in white, pink, purple, blue or even in several colours, depending on the variety. Besides the cultivar, the pH of the soil also affects the colour of flowers. In alkaline or neutral soils, the flowers appear in pink, but on acidic sites they have a blue colouring. The oppositely arranged leaves of Hydrangea serrata are strong green and taper to a point.

Hydrangea serrata varieties

Especially famous and popular is the variety Hydrangea serrata ′Bluebird′. This is a small-sized cultivar. It has purple inner flowers with blue stamens. The outer false flowers are faintly purple to blue in colour. Since flower colouring depends on the pH of the soil, it may vary somewhat depending on the location. To get the blue colour, you can read about how to dye hydrangeas blue in our matching article.

In addition to the Hydrangea serrata cultivars, there is also a wide variety of hybrid cultivars of Hydrangea serrata and Hydrangea macrophylla. Although these bear the species name Hydrangea macrophylla, they bear a close resemblance to Hydrangea serrata and are also called lacecap hydrangeas. This group includes ′Lanarth White′ and Endless Summer ′Twist-n-Shout′. Lacecap hydrangea ′Lanarth White′ is great as a container plant due to its low growth height and width of 90 to 120 cm each. Its plate-shaped flowerheads are composed of white marginal flowers and pink or blue inner flowers, depending on the soil pH. The cultivar Endless Summer ′Twist-n-Shout′ in the colour pink captivates with its dreamy pink flowerheads, which contrast wonderfully with the dark green leaves.

Other hardy lacecap hydrangea cultivars include Hydrangea macrophylla ′Libelle′ and ′Fasan′. The flower panicles of the cultivar ′Libelle′ look particularly noble. Its pink inner flowers are surrounded by pure white marginal flowers. The flowers of the variety ′Fasan′ appear in bright purple. Those who can’t decide on a colour or are looking for something unusual may enjoy a multicoloured lacecap hydrangea cultivar such as Hydrangea serrata ′Cotton Candy′. This variety has pseudo-pink flowers with small creamy white leaflets in the centre. If the soil pH is acidic, the pink can also turn a soft shade of purple to blue.

Planting mountain hydrangeas: location and timing

Hydrangea serrata, like the closely related Hydrangea macrophylla, are most comfortable in a semi-shaded, wind-protected location in the garden or on the balcony. In principle, hydrangeas can be planted throughout the year, but the ideal time is between March and June.

The hydrangeas prefer a humus- and nutrient-rich, fresh to moist garden soil with an acidic or at least slightly acidic pH between 4 and 6. An acidic soil makes it easier for them to absorb nutrients, especially iron. In fact, planting in acidic soil prevents iron chlorosis, which is common in hydrangeas. Sandy, nutrient-poor and overly alkaline garden soils should be amended with a suitable special soil such as our Plantura Organic Ericaceous Compost before planting, or replaced entirely over a large area. Very clayey soils should also be generously loosened deep in the soil, at the bottom of the planting hole with drainage material such as sand, expanded clay or perlite.

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Carefully loosen the planting ball of the lacecap hydrangea from the planting container and then loosen it a little. This stimulates root growth. After that, the root ball is placed in a sufficiently large planting hole or the prepared planter, which is filled with substrate. Press firmly and water generously. Especially with frequent high temperatures in early summer, a regular and sufficient water supply of newly planted Hydrangea serrata is essential. In addition, a mulch layer of leafy greens or bark mulch can be placed around hydrangeas to keep moisture in the soil longer. To use water even more efficiently, a circular watering rim can be formed around hydrangea plants from leftover garden soil to prevent watering water from running off to the sides above ground.

Tip: Forest gardens and those on former moorland are often already supplied with an acidic soil by the plants growing on them – so it is worth checking the soil pH here before buying a special acidic soil. However, the vast majority of garden soils do not provide optimal growing conditions for hydrangeas. Therefore, humus-rich, acidic soil is often a good investment in beautiful hydrangea blooms.

If you want to plant Hydrangea serrata in a pot on the terrace or balcony, an acidic soil such as our Plantura Organic Ericaceous Compost is also ideal as a substrate. However, in addition to the right soil, it is also important to choose a suitable container. It should be large enough, and the bottom of the container necessarily have a drainage hole, so that excess watering can easily drain off and not cause waterlogging. Glazed pots or plastic pots are more suitable for this purpose than open-pored clay pots, because they do not lose water so quickly.

Hydrangea serrata care

Hydrangea serrata, like all hydrangea species, have a decidedly high water requirement. They need to be watered regularly in the summer, possibly even twice a day on hot days. Especially for potted hydrangeas, due to the smaller volume of soil, make sure that the substrate does not dry out. Mountain hydrangeas are sometimes sensitive to lime. Therefore, it is best to use rainwater for watering. In this way, you not only do something good for your hydrangea, but also save valuable drinking water. However, if you do not have a water butt, low-lime tap water or water acidified with a small amount of peat is also suitable. To make the best use of water, in addition to the water-saving measures mentioned above (mulch layer and watering rim), it is best to water in the morning or evening when sunlight and therefore evaporation are low.

Pruning Hydrangea serrata

Lacecap hydrangeas are rarely pruned. In spring, remove the dead flowerheads just above the new buds, and frostbitten or withered parts of the plant from the bush by hand or with scissors. If Hydrangea serrata becomes too sprawling and bushy, it can be thinned out a bit by completely removing some shoots at the base.

Fertilising

Separate fertilisation is not necessarily needed for Hydrangea serrata in the flower bed, if the garden soil is good and occasionally supplied with compost. For potted hydrangeas, however, an annual fertiliser application is advisable to replenish the nutrient supply in the limited pot volume. For this purpose, our Plantura Hydrangea Food with three months of slow-release fertilisation is ideal. It provides the soil with extra iron and can prevent typical deficiency symptoms and diseases. The right time to feed tea of heaven hydrangeas is spring. Spring fertilisation will give the hydrangeas a good start to the growing season. If necessary, another dose of fertiliser can be given in the summer. In late summer and autumn or even winter hydrangea should not be fertilised, otherwise possibly increased frost damage.

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Tip: A layer of mulch, which keeps moisture in the soil longer, improves the effectiveness of hydrangea fertilizer. But be careful: hydrangeas take root very shallow. Therefore, do not work the fertilizer under the hydrangeas, as it may damage the roots.

Hydrangea serata in winter

Hydrangea serrata are hardy in our latitudes. Well-hardened plants from specialised stores are hardy and usually do not require winter protection in the flower bed. However, it is not uncommon for individual shoots to die back each year and need to be removed. In harsh locations, the shallow roots can be protected from frost with a layer of leaves or fir branches as a precaution. Lacecap hydrangeas growing in tubs should be wintered in a sheltered place, such as the corner of a house, and possibly under a roof. During prolonged low temperatures, a garden fleece or jute bag can be placed around the plants to protect them from frost damage.

Propagating lacecap hydrangeas

Hydrangea serrata, like the related bigleaf hydrangeas and other hydrangea species, can be propagated by cuttings. These are taken between June and July. Cut from the rods 10-15 cm long, weakly woody and vital shoot tips without flower buds. Then carefully remove all the leaves except for the upper pair of leaves, and then put the cuttings 2 to 3 cm deep in growing containers filled with substrate. A peat-free seedling soil such as our Plantura Organic Herb & Seedling Compost is ideal as a substrate. Adding a little sand or perlite will increase substrate permeability and improve rooting. The substrate in the growing containers must be kept continuously moist. The best way to humidify is with the help of a spray bottle. In a bright place without direct sunlight and at a temperature as constant as possible, about 15 °C, the cuttings take root and grow into new hydrangea seedlings.

If you are also interested in other types of hydrangeas, you can continue reading in our dedicated article about panicled hydrangeas and learn about interesting cultivars of this species.