Hydrangea involucrata, the dwarf peony bud hydrangea

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Hydrangea involucrata in summary:

Latin name : Hydrangea involucrata
Common name : Dwarf hydrangea
Family : Hydrangeaceae
Type : Shrub

Port : Rounded spreading
Height : 0.8 m to 1.20 m
Width : 0.8 m to 1.20 m

Exposure : Shade/partial shade
Soil : Humus-rich, light, draining, pH acid to slightly calcareous
Hardiness : Good

Growth : Slow –  Foliage : Deciduous –  Flowering : July or August to October

The Hydrangea involucrata is a dwarf shrub rarely exceeding 1 m in height, ideal for flowering a small garden or a terrace. This species has delicate serrated, flat or round inflorescences with velvety foliage close to Hydrangea aspera . The colors are pastel (mauve, white, pearly, pink) and do not change with the nature of the soil as with Hydrangea macrophylla . The buttons are themselves very decorative by their volume which evokes peony buttons. Native to Japan and Taiwan, its cultivars often bear Japanese names like ‘Yoraku Tama’ or ‘Hanabi Tama’ .

Planting Hydrangea involucrata

The necessary conditions for good growth of Hydrangea involucrata are:

  • cool atmosphere , protected from cold and dry winds, with exposure to shade or partial shade ;
  • soil rich in organic matter, acid to slightly calcareous, unlike other Hydrangeas, and draining.
  • The dwarf hydrangea tolerates frosts down to -18°C.

When to plant?

Favor an autumn planting to allow your Hydrangea involucrata to recreate a root system capable of better supporting the lack of water during the following seasons.

However, you can plant your shrub in the spring , but you will then have to take care to maintain good humidity in the soil.

Planting in the ground:

  • Dig a hole about thirty centimeters deep.
  • If necessary, amend the soil by adding heather earth and sand.
  • Remove the pot from the foot of the Hydrangea involucrata and break up the root ball, paying attention to the roots. This operation allows them to grow outside the original soil.
  • Install the foot in the planting hole and fill it in by packing the soil well (watch out for the roots).
  • Water copiously.

 Potted Hydrangea involucrata :

  • Start by choosing a large enough container with a water supply to limit watering.
  • Check for the presence of water drainage holes and create them if they are absent.
  • Make a mixture of heather earth and potting soil, to which you can add perlite (also called vermiculite). It will facilitate water drainage and retain moisture in the substrate.
  • Add a layer of drainage to the bottom of the pot, without blocking the water drainage holes and complete with your potting soil/Heath earth mixture.
  • Plant your Hydrangea involucrata in a pot , following the same instructions as for planting in the ground.

Tip : Whatever planting method is used, do not hesitate to  mulch the surface of the soil around the base of the shrub. Mulch effectively limits water evaporation and retains moisture in the soil.

The perfect mulch for a hydrangea is pine bark, which helps maintain a certain acidity in the soil.

Smart advice

If you cannot find a container with a water reservoir, place a container such as a bowl or a large saucer at the bottom of the pot, without blocking the drainage holes. It will recover excess watering and return it as needed.

Maintenance and pruning of the dwarf hydrangea

The sensitive part for the maintenance of a hydrangea is undoubtedly the size :

  • Should you prune?
  • If so, during what period? How ?

For the Hydrangea involucrata , it is very easy, you must prune in late winter or early spring. Cut all the branches to half their length or even to ground level because flowering is done on the wood of the year. It has the advantage that a late frost has little effect on flowering because the shrub flowers on the shoots of the year.

The flowers are quite late and last a long time. They do not need to be cut until spring pruning.

  • Pruning hydrangeas, to go further

When it comes to watering , be sure to keep the soil cool because the peony bud hydrangea is native to the humid high-altitude forests of Japan and Taiwan.

Multiplication

The Hydrangea involucrata propagates by cuttings on soft wood at the end of summer.

Diseases and pests

Powdery mildew and rust can attack the leaves in humid and hot weather, but without consequence for the shrub. Parasites and pests that can be problematic are bedbugs , aphids and spider mites .

Jobs

The Hydrangea involucrata is a rare species and quite delicate if the conditions of freshness and humidity are not met. However, its uses are many. You can install it in a large pot on a terrace or near a shady wall, in an undergrowth, in a bed or a cool rockery associated with hostas, ferns, knotweed, Thalictrum or with other hydrangeas. The Hydrangea involucrata ‘ Late Love’ variety is one of the most vigorous, reaching 1.80 m in all directions with mauve and white inflorescences 20 cm in diameter!

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