Kerria
In Japan, it is called the Japanese rose. In England – a miracle calendula. In its short history in European landscaping, two varieties of this plant have won awards from the Royal Horticultural Society. We are talking about kerria, a beautiful, sunny and in many ways unique plant.

The genus Kerria has only one species – Kerria японская (Kerria japonica). This shrub got its name in honor of the English botanist William Kerr, who created the first variety with double flowers – Pleniflora.

Kerria is valued for its bright, dazzling yellow corollas, abundant and long flowering, bright green flexible shoots and fast growth. As a rule, it is a shrub up to 2 – 2,5 m high, but in the conditions of Central winters and freezing at the level of snow cover, it rarely exceeds 1 m. Due to root offspring, the bush quickly grows into a large curtain. Shoots are straight, thin, twig-shaped with bright green bark in winter, they acquire yellowish hues. Leaves lanceolate, up to 10 cm long, with a sharp tip and serrated edge, bright green   

The flowers are large, five-leafed or double, bright yellow, covered with whitish strokes in the sun. Flowering begins in May and lasts about a month, and with good care and proper pruning, terry varieties begin to bloom again. By the way. double flowers look like miniature roses, fluffy pompoms or, as they say in England, “bachelor’s buttons”.

Kerria in the conditions of central Our Country suffers from frost and needs shelter. However, if the plant freezes at the level of the snow cover, it is enough to cut off the affected shoots and the shrub will quickly recover. But flowering will be weak. Varieties and forms with variegated foliage require careful care and reliable shelter, so they are rarely used in ordinary gardens.

Kerria shoots are thin and suffer greatly from the winds, so it is important to use the plant correctly in landscape design – under the protection of larger trees and shrubs. It looks especially good against the background of coniferous crops, shrubs with dark foliage. During flowering, kerria looks especially impressive next to perennial spring phlox and blue irises.

Varieties of kerria

In garden centers, the assortment of kerria is most often limited to 2 varieties, and even a natural form with simple flowers can occasionally be found in parks and amateur gardens. 

Golden Guinea. Кold plant up to 2 m high and 1,5-2,5 m wide with thin, drooping branches. Due to the shoots, it forms large clumps with branches covered with bright green leaves with a serrated edge and prominent veins. It blooms in May-June for 4-5 weeks with yellow simple flowers up to 6 cm in diameter. Frost resistance up to -29 ° С.

Albiflora. Similar to Golden Guinea, but her flowers are white.

Pleniflora (Plenary). Dense shrub up to 2 with straight thin but strong shoots with bright green leaves. Forms clumps quickly. Blooms profusely for more than 1 month in May-June, after pruning, weaker flowering occurs in September. Flowers up to 4 cm in diameter are bright yellow double. Frost resistance up to -29 °С.

Variegata (pictured). Shrub with simple bright yellow flowers, grey-green leaves edged with a cream stripe. There is a form with cream flowers – Picta Silver. Frost resistance up to -23 °С.

Albomarginata. Shrub with simple bright yellow flowers, gray-green leaves with a white border. Frost resistance up to -23 °С.

Golden-variegated. Shrub with double yellow flowers and leaves with a yellow border. Frost resistance up to -23 °С.

Kerria Care

Kerria is easy to care for, but in order for it to decorate the garden and bloom profusely, it is important to choose the right landing site and properly prepare the planting hole. The plant is very sensitive to cold winds and prolonged frosts, it suffers from deepening of the root neck during planting.

Ground

For successful cultivation of kerria, loamy, moderately moist soil, fertile and well-drained, is preferred. The reaction of the soil solution is neutral or slightly alkaline.

Lighting

Abundant flowering is possible when planting kerria in well-lit places. However, in the bright midday sun, the tips of the petals burn out on the flowers. If you want to preserve the purity of the color, you should plant the kerria so that at noon an openwork shadow from the trees falls on it.

The plant also feels good when planted in partial shade, but flowering will be weaker. When planting, it is important to consider spatial isolation so that closely growing plants do not greatly obscure the lower part of the bush.

Watering

Kerria belongs to moisture-loving plants, however, it does not tolerate excessive moisture, and even more so, stagnant water in the root zone. Therefore, drainage and optimal watering are important. The soil should always be slightly moist, during flowering in hot weather it should be watered abundantly.

fertilizers

For growing kerria, complex mineral fertilizers, wood ash and dolomite flour are used.

Feeding

For the kerria season, you need to give 4 top dressings:

  • spring – any complex mineral fertilizer: 30 – 40 g (2 tablespoons) under a bush;
  • before flowering and after flowering – 10 liters of mullein infusion (1:10) per 1 bush in tree trunks;
  • in August – wood ash at the rate of 100 – 200 g (1 – 2 cups) per bush.

And at the end of September, the bushes should be mulched with matured compost or humus.

Trimming

Kerria needs regular pruning. In addition to the most important sanitary, when in the spring it is necessary to remove all broken and frost-damaged shoots, the shape of the bush should be maintained. To do this, cut out excess shoots, thickening the middle of the bush shoots, remove all branches aged 4-5 years and older.

To stimulate flowering in spring, shoots are shortened by 1/3, which leads to the appearance of side branches on which flowers form. And after the end of flowering, cut out the shoots on which there were flowers to the shoots on which there was no flowering. This technique causes repeated flowering in the fall.

Shelter for the winter

Kerria needs special preparation for winter. Before the soil freezes, the trunk circle must be mulched with humus or compost. In early November, the shoots are tied into bundles, bent to the ground, placing a dry plank or piece of foam under them, pinned, covered with a dry sheet or shavings.

Above the bush, it is desirable to build a frame of stakes or metal arcs, on which a dense non-woven material can be pulled in two layers. It is very important that under the shelter it is dry and the air does not stagnate.

In the spring, the shelter is removed gradually, when the soil begins to thaw. 

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Reproduction of kerria

Amateur gardeners most often propagate kerria by cuttings (a very high degree of rooting), layering or offspring.

Cuttings. Cuttings 10-12 cm long are cut in June from a one-year growth. Remove the lower leaves, make an oblique cut, dust it with Kornevin powder and plant it in light soil on a seed bed or in pots   

The cuttings are covered with a film, regularly sprayed and ventilated. As soon as the growth of new leaves begins, the shelter is gradually removed. 

Pots with cuttings are instilled in the distribution bed and well covered with a dry leaf. In the spring, rooted cuttings continue to grow and only in the fall or next spring are they planted in a permanent place.

Kerria is also grown from lignified cuttings, which are cut in April.

Layers. For propagation by layering, in early spring after the opening of the bushes, a flexible shoot is chosen, placed in a groove, fixed and waiting for the shoots to appear from the buds. As soon as they reach 10 – 15 cm, the groove is filled with moist fertile soil, falling asleep and shoots to 1/2 of the height. In autumn or next spring, the grown bushes are separated and planted in a permanent place.

Offspring. Offspring appear in large numbers in adult bushes, especially if they have suffered from severe frost. They are separated from the mother bush with a sharp shovel, cutting off the root extending from it, carefully dug up and planted in a permanent place. To enhance the development of the bush, the shoots are shortened by 1/3.

Kerria diseases

There are no signs of disease on kerria bushes in central Our Country.

Kerria pests

Practice shows that in central Our Country, kerria is not damaged by pests.

Popular questions and answers

We asked about Kerria agronomist Oleg Ispolatov – he answered the most popular questions of summer residents.

How to choose kerria seedlings?

Seedlings with an open root system are bought in early spring or September – this is the best time to plant them. The root system should be well developed, without breaking and dry areas.

 

Seedlings with a closed root system can be planted at any time, but no later than October. It is important that the aerial part is bushy enough, and the roots do not grow through the drainage holes.

How to use kerria in landscape design?

Thanks to the bright green stems, kerria is good not only at the time of flowering. It looks great against the background of the lawn, both in a single landing and in groups. Creates a beautiful backdrop for low blue to blue flowered perennials. It looks impressive at the time of flowering against the background of vesicles with purple or brown-red leaves.

What to do with kerria in the fall?

Moisture-charging watering, mulching the near-stem circle and dry shelter of bushes are the most important stages in preparing a plant for a successful wintering.

What to do with kerria in winter?

In a winter with little snow, dry snow is thrown on the kerria bushes. In snowfalls, make sure that shelter does not sag under wet snow.

What to do with kerria in spring?

As soon as the soil begins to thaw, the edges of the winter shelter are slightly opened, and in cloudy weather they begin to remove it and raise shoots. To prevent sunburn, a shading net is thrown over the bush. Sanitary pruning. Complex mineral fertilizer is scattered on wet ground.

Sources of

  1. Aksenov E., Aksenova N. Ornamental gardening for amateurs and professionals. Trees and shrubs // M.: AST-Press, 2001
  2. Kerria // The Plant List

    http://www.theplantlist.org/1.1/browse/A/Rosaceae/Kerria/

  3. State catalog of pesticides and agrochemicals permitted for use on the territory of the Federation as of July 6, 2021 // Ministry of Agriculture of the Federation

    https://mcx.gov.ru/ministry/departments/departament-rastenievodstva-mekhanizatsii-khimizatsii-i-zashchity-rasteniy/industry-information/info-gosudarstvennaya-usluga-po-gosudarstvennoy-registratsii-pestitsidov-i-agrokhimikatov/

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