Japanese dogwood

The Japanese dogwood (Cornus kousa subsp. kousa), similar to the Chinese dogwood (Cornus kousa subsp. chinensis) is a sub-species of the Asian dogwood (Cornus kousa). In its garden form it is considered one of the richest flowering of the group of Dogwoods. For the sake of simplicity, the Japanese dogwood is often simply designated as the Cornus kousa, although this can be slightly confusing. Therefore, it is important to take note of the exact botanical designation when making a purchase.

The slow growing bush or tree can reach heights of 13 to 20 feet. The main branches emerge vase-shaped, the side branches are arranged in tiers and if they are left to grow free, they become sweeping on older trees. The bark on the trunk of the Cornus kousa is gray. Young shoots are slightly hairy, this disappears later.

The Japanese dogwood’s oval leaves taper to a point at the tip, are dark green with a full margin and arranged opposite one another. For a Dogwood, they have striking arch-style running leave veins. The leaves grow to around 4.33 inches long, 1.97 inches wide and have fine hair. The deciduous shrub has a vibrant red fall foliage. The Cornus kousa loses its foliage in the winter.

While the actual flowers - small, yellowish-green, round umbels - are rather unspectacular, they make the cream white bracts which surround the flowers all the more appealing. The palm sized flowers of the Cornus kousa are actually pseudanthiums. The Japanese dogwood blooms from May to into July, depending on its location.

An orange-red pseudo-fruit up to 0.79 inches in diameter develops from the flower umbels. The fruit sits on long stems and is edible, but tastes rather bland. In Japan they are eaten raw and pickled or used to make a sort of fruit liquor.

In the garden, the shrub needs a sheltered, sunny to semi-shady or off-sunny space. In free nature, the Japanese dogwood is found on the edges of forests and river banks, therefore, it also prefers a sheltered and humid space in the garden.

Cornus kousa thrives best in fresh, sandy-humus, slightly acidic soils. However, the flowering shrub dislikes waterlogging and calciferous soils, it also often struggles to grow in heavy, loamy soils.

In containers, Japanese dogwood can be planted at any time of year when there are no frosts. However, it is recommended to plant in the spring, from February to the end of March, as the plant will then require less watering. It can also be planted during the fall, however, you should protect very young plants against frost with some leaves and pine brushwood or winter fleece. It is generally better to plant dogwood too shallow rather than too deep. The pot or root ball should be flush with the soil or even stand a little proud. If the soil is not acidic enough, the substrate in the planting hole should be made more acidic with a little Rhododendron soil or leaf mulch compost. It is recommended to enrich all soils with humus, as all dogwoods do visibly better in humus-rich soils.

All in all, the Japanese dogwood is very easy-care and robust, both against late frosts and also heat and dryness. After planting, the Cornus kousa should be regularly watered during the first year when there is a lasting dry spell. If the shrub has rooted well, additional watering is no longer necessary. A mulch layer or low competition under-planting – for example, with heart leaf foam flowers (Tiarella cordifolia) – also protects the flat root shrub from drying out. Adding horn shavings in the spring enriches the soil with nitrogen. Avoid hoeing and digging in the root area of the plant in order to prevent damage to the flat roots near the surface - this will make the shrub more and more beautiful with ever more abundant flowers over the years.

There is no need to prune the Cornus kousa, as the shrubs grow very slowly and are correspondingly weak at regenerating. Moreover, pruning has hardly any effect on the flower development. Corrective pruning is only recommended for young plants in order to promote a harmonious crown development. Bothersome branches can also be removed from older plants at any time - preferably right after flowering.

Japanese dogwood flowers are so unique that they are generally planted as solitary shrubs, for example as a home tree or individually in a lawn. They are extremely effective as background in shrub beds. When combining with other flowering shrubs, you should take care not to choose a shrub as a plant partner which flowers at the same time as the Japanese dogwood, so it doesn’t steal the show. The plant partner should also not be too competitive - a proven good neighbor, for example, is witch hazel. Cornus kousa can also stand on the terrace as a container plant.

If you wish to obtain a real Japanese dogwood for your garden, you can easily fall into the trap of poor designations in the trade. Because often the Cornus kousa subsp. kousa as well as the Cornus kousa subsp. chinensis (Chinese dogwood) are sold as ‘Japanese dogwood’ and even Cornus florida hybrids are also sometimes included in the same pot. If you are in doubt, look at the precise botanical designation.

The wild species of the Japanese dogwood propagate through cuttings or seed sowing. If you wish to extract the seeds from the fruit, you must completely remove the surrounding fruit flesh as it contains inhibiting substances which reduce the germination rate. However, the hybrids and varieties of Cornus kousa often found commercially can only be propagated through grafting - the Chinese dogwood are usually used as a basis, as these grow a bit more readily.

The Japanese dogwood is very robust against diseases. Even the dogwood owners feared fungal infection anthracnosis causes the Cornus kousa no problems, provided the location suits the shrub. Infestations of Mildew or leaf spots are occasionally observed. Pests generally occur rarely, if at all, on the beautiful flowering shrub.