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Kerria japonica is the only species in the genus Kerria. In its natural form, it is an upright growing shrub with carved leaves and simple 5-petalled flowers. The decorative appearance of the bush contributed to the fact that the plant became widespread in gardens. The most popular among gardeners is 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 by clinging to rocks or other vegetation. In gardens, shrubs require 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. The wild form has golden yellow flowers.
At a young age, the bush has a pyramidal shape, but with age the shoots lengthen and bend downwards, forming an arch.
Today there are several varieties of garden kerria, and the most popular is Pleniflora. This is a dense shrub with “double” flowers - a mutational form of the usual Japanese kerria.
Single flowers have a diameter of up to 3 cm and grow from the axils of the leaves. The 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 occurs in late May and early June. The kerria blooms for the second time at the end of summer. Flowers appear on the shoots of the current and previous years.
Kerria japonica in landscape design
Photos of Japanese kerria in landscape design and a description of its unpretentiousness make the plant attractive to summer residents who want to create a hedge on their property. Dense bushes hide the hard base of the fence well.
Since the bush grows up to 3 m, the height of the fence can be varied. Most often in gardens, kerria is trimmed at a level of 1 m from the ground.
When creating a composition of shrubs, kerria goes well with a variety of plants:
- Japanese maple;
- meadowsweet;
- forsythia;
- rhododendron;
- mahonia;
- vesicular carp;
- spirea;
- action;
- Kuril tea;
- weigela;
- coniferous shrubs.
Japanese maple is a tree in natural conditions. But in gardens it is usually a powerful, tall shrub 8-10 m high.
A kerria bush will look good surrounded by spring and autumn flowers:
- watershed;
- tulips;
- egonychon purple-blue;
- dwarf irises;
- hazel grouse;
- phlox;
- forget-me-nots;
- buzulnikov;
- periwinkles;
- camellia.
There are a lot of options with flowers. You just need to select the flowering time of the plants and the appropriate color scheme.Moreover, the latter is usually a matter of taste between the designer and the customer.
Growing conditions for Japanese kerria
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.
Kerry shoots are fragile and can break under strong winds. Planted as a solid wall in a green hedge or together with other, stronger bushes, the 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 protected from strong winds.
Planting and caring for Kerry Japanese Pleniflora
For planting kerria, select an area that is not too shaded, but also not exposed to the sun. The best option would be to plant the plant in the shade of trees with a not very dense crown or where the sun peeks only at dawn or sunset.
Kerria propagates by cuttings, layering and young shoots. Since all these methods of propagation involve planting a “ready” plant with roots, it is necessary to prepare a pit with fertile soil in advance for the kerria.
Soil preparation
Kerria japonica grows best in loamy soils that can absorb and retain large amounts of moisture. If the type of soil in the area is different, Pleniflora will not die, although flowering will not be as abundant.
But this is the “base” that almost cannot be changed. Heavy soil can be improved by adding sand, and infertile soil can be improved by adding fertilizer.And also fill the planting hole with soil, which will help the plant take root. There are two recipes for soil for a hole:
- 3 parts of sand and 1 part each of compost, turf soil and humus, add 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 0.6x0.6 m.
The second composition is more suitable for areas with loamy soil.
Preparation of planting material
If the Pleniflora seedling was purchased along with a pot in a store, then no preparation is necessary. It is enough to shake the kerria out of the pot along with a lump of earth and plant it in a permanent place using the transshipment method. The same applies to cuttings that were rooted in a pot at home.
When purchasing a seedling from hand with an exposed root system, the plant is inspected and dried and rotten parts are removed. You can place the seedling for several hours in a solution with a root growth stimulator.
When digging up planting material yourself (propagation by layering), you should try to remove the seedling along with the soil so that damage to the young root system is minimal.
Preparing the landing site
In the selected area, dig a hole with a diameter of 60 cm and the same depth. Soil is poured into the hole so that a slide is formed. Later the soil will settle and become level with the ground.
If the planting site is too wet, the hole is made deeper and a thick layer of drainage material is poured onto the bottom: broken bricks, pebbles, etc.
If you carry out all the work 6 months before planting, not only will the soil in the hole be compacted, but also the fertilizer will be distributed more evenly.For Kerria japonica, a large amount of fertilizer in the first 2 years after planting can be dangerous.
Landing rules
Planting of 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 transfer in compacted soil, make a hole the size of a lump of earth from a pot. Place the lump at the bottom of the excavation and sprinkle it with soil for stability.
When planting a Pleniflora seedling with an exposed root system, you must ensure that the roots of the bush do not break. In this case, it is better to plant together: one person holds the plant “in weight”, the second covers the roots with soil.
After planting, the soil is lightly compacted and the seedling is watered. For the first 2 weeks, the soil under Pleniflora is kept constantly moist.
Watering and fertilizing
Kerry needs to be watered regularly during the flowering period and during the dry period. 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 abundantly.
Feeding is a little more complicated. Kerria is considered an unpretentious shrub that does not require large amounts 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 applying fertilizing are the same as for other plants: you can add fertilizers before winter, or you can add them with spring watering.
Sometimes kerria is fed with mullein infusion in the spring, and after summer pruning with complex fertilizers.
Trimming
The rules for pruning Pleniflora are simple: spring sanitary and after the first flowering.Sanitary pruning is carried out in early spring, before the buds have time to swell. Remove all dead and diseased shoots. If necessary, thickening stems are cut out, annual branches are cut to ¼-⅓ length.
Repeated pruning is done in order to make Pleniflora bloom more luxuriantly the second time. If such a goal is not worth it, the kerria does not need to be cut a second time.
During the second pruning, those branches that had flowers are removed. They are cut back to the shoots that had no flowers in the spring. In this case, new flowering shoots will grow over the summer, and Pleniflora will bloom magnificently again.
Kerria shoots grow until mid-autumn, and for normal wintering these shoots must ripen.
Preparing for winter
The winter hardiness of Japanese Pleniflora kerria is not very high, although in the southern regions it does not need any shelter for the winter. In a windless place, it can overwinter without shelter.
If you need to close Pleniflora for the winter, you cannot use airtight materials. Tarpaulin or plastic wrap will not work. Nonwoven materials will do: 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 they cover it 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
Kerria japonica can produce small seeds measuring 4-4.5 mm. But propagation in this way is not practiced in gardening due to its low efficiency.Usually Pleniflora is propagated in 3 ways:
- dividing the mother bush;
- cuttings;
- layering.
Dividing the mother bush is just so called. In fact, in the spring or autumn, the side shoots are carefully dug up and planted in the usual way in prepared holes.
Propagation by cuttings
In late spring, annual shoots that have already become lignified are cut into pieces 6 cm long. The cuts are made oblique. The cuttings are buried in a shaded 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. The growing shoots are carefully placed there, without cutting them off from the bush, and pinned to the ground.
After 15 days, new shoots appear from the buds of shoots pinned to the ground. When the shoots become 10-15 cm high, the grooves are covered with earth. Only the tips of new shoots should remain on the surface. In the spring of next year, young bushes can be planted in a permanent place.
Diseases and pests
Kerria japonica is little susceptible to diseases and pests. At least, ordinary pathogenic microorganisms do not affect kerria. But since 2014, the UK Horticultural Society began to receive reports of cases of Kerry disease. Signs of the disease are red spots on the leaves and damage to the stems. The disease causes discoloration and drying out of color and possibly 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 only affects Japanese kerria.
Conclusion
Kerria japonica 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 by creating a whole green hedge from one bush.
