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One of the brightest shrubs of spring, kerria is an old favourite, easy to grow and reliable. Kerria is the botanical name and it is part of the rose family.
The pretty flowers have something of a rose shape, or the shape of the flowers of raspberry or bramble, and those are also part of the rose family.
It is native to Japan, Kerria japonica being its full name. The kerria part honours an 18th century British botanist called William Kerr. So this shrub has been around for a long time.
Structure
The bright golden flowers are up to 5cm across with five petals. These rounded petals are held slightly separated around a boss of pollen-carrying stamens, making an almost flat or slightly cupped shallow flower.
There is a lovely variety, aptly named ‘Golden Guinea’, which has large single flowers.
The form that was popular in traditional country cottage gardens was the double-flowered form known as ‘Pleniflora’, which means full-flowered.
In this form, most, or perhaps all, of the boss of feathery stamens have turned to narrow petals. There are so many of these narrow petals that the flowers take on a rounded, pom-pom shape.
Both the single-flowered and double-flowered forms are vigorous and capable of growing to three metres tall.
There is a variegated form called ‘Picta’, with white variegation along the margins of the leaf, and this one is less vigorous and makes small single flowers, really only grown for its foliage.
But it often reverts back to the original plain green foliage. This occurs when a bud on a variegated shoot mutates in reverse.
The green form has more chlorophyll and is more competitive, eventually ousting the weaker variegated sort if the green shoots are not taken out before they get going.
Kerria is deciduous but has green shoots, almost rush-like, and makes a big stack of bright green shoots, arching outwards at the top.
In spring, the brassy yellow flowers are produced near the tips of the young shoots.
Hardy
It comes from colder parts of Japan and the Far East and it is extremely hardy.
But too much exposure to wind and the consequent chafing of the stems against each other can cause die-back of the stem tips, which reduces flowers and gives the plant a half-dead look, so some shelter is a good idea.
The shrub is not choosy about soil and will grow easily in most conditions that are not too wet in winter or baked dry in summer.
The double-flowered form tends to scald in full sunshine but this can be avoided if the sun passes off it for part of the day.
It is a tall shrub and usually best placed in the background where it will not be obvious when out of flower, as then it is pretty unremarkable.
It can be pruned immediately after flowering and cut back hard if it gets out of control.
It spreads to make a narrow thicket by means of suckers and these spread outwards steadily, extending the ground that the individual plant controls.
Suckers can be easily dug up for new plants or they can be chopped out with a spade to control the spread of the plant.
Cottage gardens
Like any suckering shrub, it has been widely passed around, which is why it was popular in cottage gardens.
No money was spent on plants in an old-style cottage garden, so plants that were easily raised from suckers, seeds, cuttings or divisions were grown, including kerria.
Many old plants can be spotted in flower in gardens in the coming weeks.
This is tree planting time as growth will begin soon. Already the catkins are open on hazelnut, and some early cherries have flowers.
The buds of other species are swelling and roots are active too, in perfect timing for growth. All kinds of trees and shrubs can be planted in the coming weeks if the soil has dried out enough.
When planting from pots it is important to unwrap roots that have wound their way around the inside surface of the pot. It they are left as they are, it can prove to be a fatal weakness that can cause trees and shrubs to be rocked, loosened and even blown down when much older.
The problem is more evident with conifers but can occur with most species. Simply rip out some of the roots or slice through them with an old knife.
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