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Kerria japonica is the only species in the genus Kerria. In its natural form it is an upright shrub with carved leaves and simple 5-petal flowers. The decorative appearance of the bush contributed to the fact that the plant became widespread in gardens. The most popular among gardeners is the Japanese kerria Pleniflora with double flowers and beautiful carved leaves.
Description of Kerry Japanese Pleniflora
Kerria grows up to 3 m in height. The branches are weak, arched. Under natural conditions, the shrub often grows clinging to rocks or other vegetation. In gardens, shrubs need support.
The leaves are simple, 3-10 cm long. The edges are double serrated. The upper side of the leaf is smooth, the lower side is covered with hairs. In the wild form, the flowers are golden yellow.
At a young age, the bush has a pyramidal shape, but with age, the shoots lengthen and bend down, forming an arch.
Today, there are several varieties of garden kerria, and Pleniflora is the most popular. This dense shrub with “double” flowers is a mutational form of the common Japanese kerria.
Single flowers have a diameter of up to 3 cm and grow from the axils of the leaves. Flowering is lush. Since the shoots are completely covered with yellow fluffy flowers, the leaves of Pleniflora are almost invisible at this time.
The bush blooms 2 times per season. The most magnificent flowering is in late May and early June. The second time kerria blooms at the end of summer. Flowers appear on the shoots of the current and last years.
Kerria Japanese in landscape design
A photo of Japanese kerria in landscape design and a description of its unpretentiousness make the plant attractive for summer residents who want to create a hedge to grow on their site. Dense bushes hide the rigid base of the fence well.
Since the bush grows up to 3 m, the height of the hedge can be varied. Most often in gardens, kerria is cut at a level of 1 m from the ground.
When creating a composition from kerria shrubs, it goes well with many plants:
- Japanese maple;
- the devil;
- forsythia;
- rhododendron;
- mahonia;
- vesicle;
- spirea;
- action;
- Kuril tea;
- weigela;
- coniferous shrubs.
Japanese maple – a tree in natural conditions. But in gardens, it is usually a powerful tall shrub 8-10 m high.
A kerria bush surrounded by spring and autumn flowers will look good:
- catchment;
- tulips;
- egonychon purple-blue;
- dwarf irises;
- hazel grouse;
- phloxes;
- forget-me-not;
- buzulnikov;
- periwinkles;
- camellia.
There are a lot of color options. You just need to choose the time of flowering plants and the right color scheme. Moreover, the latter is usually a matter of taste of the designer and the customer.
Conditions for growing kerria japonica
Kerria is not afraid of the sun, but its flowers turn pale in direct sunlight, so it is preferable to plant kerria in the shade. The plant is moisture-loving, but does not grow in swamps, so stagnant water should also be avoided.
Kerria shoots are brittle and can break in strong winds. Planted as a solid wall in a green hedge or along with other, stronger bushes, kerria will be protected from this problem.
It is better not to plant Japanese kerria separately from other shrubs. Even if in landscape design the combination of a bush strewn with yellow flowers and forget-me-nots blooming on the ground looks very beautiful. But such a composition can only be created in a place closed from strong winds.
Planting and caring for Kerria Japanese Pleniflora
For planting kerria, a site is selected that is not too shaded, but not in the sun either. The best option would be to plant the plant in the shade of trees with a not very dense crown, or where the sun looks only at dawn or sunset.
Kerria propagates by cuttings, layering and young shoots. Since all these methods of reproduction involve planting an already “finished” plant with roots, it is necessary to prepare a pit with fertile soil under the kerria in advance.
Soil Preparation
Japanese kerria grows best on loamy soils that can absorb and retain large amounts of moisture. If the type of soil on the site is different, Pleniflora will not die, although flowering will not be so plentiful.
But this is the “base” that is almost impossible to change. You can improve heavy soil by adding sand, and infertile soil by adding fertilizer. And also fill the hole for planting with soil, which will help the plant take root. There are two potting soil recipes:
- 3 parts of sand and 1 part of compost, soddy soil and humus to flavor 60-80 g of complex fertilizer;
- mix garden soil with a bucket of compost, add a glass of ash and 60-80 g of complex fertilizer. The calculation is given for a pit measuring 0,6×0,6 m.
The second composition is more suitable for a site with loamy soil.
Preparation of planting material
If the Pleniflora seedling was bought along with the pot in the store, then no preparation is necessary. It is enough to shake the kerria out of the pot along with a clod of earth and plant it in a permanent place by transshipment. The same applies to cuttings that have been rooted in a pot at home.
When buying a seedling from hands with a bare root system, the plant is inspected and dried and rotten parts are removed. You can put the seedling for several hours in a solution with a root growth stimulator.
When digging up planting material on your own (reproduction by layering), you should try to take out the seedling along with the ground so that damage to the young root system is minimal.
Site preparation
At the selected site, they dig a hole with a diameter of 60 cm and the same depth. Soil is poured into the pit so that a hill forms. Later, the soil will settle and level with the ground.
If the landing site is too wet, the pit is made deeper and a thick layer of drainage material is poured onto the bottom: broken brick, pebbles, and so on.
If you carry out all the work 6 months before planting, not only will the soil in the pit be compacted, but fertilizers will be more evenly distributed. For Japanese kerria, a large amount of fertilizer in the first 2 years after planting can be dangerous.
Rules of landing
Planting kerria is carried out in the fall at least a month before the onset of frost or in the spring before the start of sap flow. For almost all plants, autumn planting is considered less traumatic.
When planting by transshipment in compacted soil, a recess is made the size of a clod of earth from a pot. Put a lump on the bottom of the recess and sprinkle with soil for stability.
When planting a Pleniflora seedling with a bare root system, it is necessary to ensure that the roots of the bush do not break. In this case, it is better to plant together: one person holds the plant “on weight”, the second one covers the roots with earth.
After planting, the ground is lightly tamped and the seedling is watered. For the first 2 weeks, the soil under Pleniflora is kept constantly moist.
Watering and top dressing
Kerria needs to be watered regularly during the flowering period and during the dry season. Water Pleniflora once a week. In rainy years, Japanese kerria does not need watering. In an average year, Japanese kerria is watered 2-3 times during the summer, but plentifully.
Feeding is a little more difficult. Kerria is considered an unpretentious shrub that does not require a lot of fertilizer. Some gardeners recommend not feeding Pleniflora at all for the first 2 years, so as not to burn its roots.
But otherwise, the rules for fertilizing are the same as for other plants: you can add fertilizer before winter, or with spring watering.
Sometimes kerria is fed in spring with mullein infusion, and after summer pruning with complex fertilizers.
Trimming
Pleniflora pruning rules are simple: spring sanitary and after the first flowering. Sanitary pruning is carried out in early spring, until the buds have had time to swell. Remove all dead and diseased shoots. If necessary, thickening stems are cut out, annual branches are cut to ¼-⅓ length.
Re-pruning is done in order to make Pleniflora bloom more magnificently the second time. If such a goal is not worth it, the kerria can not be cut off a second time.
In the second pruning, those branches on which there were flowers are removed. They are cut to shoots on which there were no flowers in the spring. In this case, new flowering shoots will grow over the summer, and Pleniflora will bloom magnificently again.
In Kerria, shoots grow until mid-autumn, and for normal wintering, these shoots must mature.
Preparation for winter
The winter hardiness of the kerria of the Japanese Pleniflora is not very high, although in the southern regions it does not need any shelter for the winter. In a calm place, she can overwinter without shelter.
If it is required to close Pleniflora for the winter, then airtight materials cannot be used. A tarp or plastic wrap will not work. Non-woven materials will fit: lutrasil, spunbond and other similar ones. But even they are not always needed. Sometimes you can get by with spruce branches and snow.
The shoots are tied and, if possible, bent to the ground. Then covered with spruce or pine branches. This operation is carried out when the air temperature drops below 0. As soon as the opportunity arises, the kerria is covered with snow.
Pleniflora does not like stagnant air and may die.
Reproduction
Japanese kerria can produce small seeds 4-4,5 mm in size. But reproduction in this way is not practiced in horticulture due to low efficiency. Usually Pleniflora is propagated in 3 ways:
- division of the mother bush;
- cuttings;
- layering.
The division of the mother bush is only called that. In fact, in spring or autumn, side shoots are carefully dug up and planted in the usual way in prepared pits.
Reproduction by cuttings
In late spring, annual, but already lignified shoots are cut into pieces 6 cm long. The cuts are made oblique. Cuttings are dug in a shady place and watered well throughout the summer. In September and early October, rooted cuttings are planted in open ground. New plants are planted in a permanent place in the spring of next year.
Breeding by layering
In early spring, in parallel with sanitary pruning, grooves are made in the ground next to the Pleniflora bush. Growing shoots are carefully laid there, without cutting them off from the bush, and pinned to the ground.
After 15 days, new sprouts appear from the buds of shoots pinned to the ground. When the shoots become 10-15 cm high, the grooves are sprinkled with earth. Only the tops of new shoots should remain on the surface. In the spring of the following year, young bushes can already be planted in a permanent place.
Diseases and pests
Kerria Japanese is not very susceptible to diseases and pests. At least, ordinary pathogenic microorganisms do not touch kerria. But since 2014, the horticultural society of Great Britain began to receive reports of cases of kerria diseases. Signs of the disease are red spots on the leaves and damage to the stems. The disease leads to discoloration and drying of color and, possibly, to the death of the entire bush.
This disease was known in the USA under the name “kerria leaf and stem rot” but had not previously been recorded in Europe. The disease is caused by the fungus Blumeriella kerriae, which affects only Japanese kerria.
Conclusion
Kerria Japanese Pleniflora can become a real decoration of the garden. She is not only beautiful during the entire growing season. It is also undemanding to care and soil. It is easy to propagate, creating a whole green hedge from one bush.