Kerria japonica

Japanese Kerria

Rosaceae

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Habitat

  • hardy to zone 5
  • useful in zone 4 with snow cover
  • native to Japan and China

Habit and Form

  • a deciduous shrub
  • produces lots of fine, slender twigs
  • stems are upright and arching
  • suckers freely and can colonize areas
  • 3' to 6' tall with up to a 10' spread

Summer Foliage

  • alternate, simple leaves
  • leaves are ovate to lance-shaped
  • leaf margins doubly serrate
  • 1.5" to 4" long
  • bright green color
  • crisp texture

Autumn Foliage

  • leaves hold late into fall
  • some clear yellow leaves, some leaves just drop green

Flowers

  • showy bright yellow flowers
  • about 1.5" across
  • 5-petaled
  • borne singly
  • blooms in late April and may
  • sporadic bloom after the primary blooming period can occur
  • in sun, the flowers fade to a bleached color

Fruit

  • rarely sets fruit
  • not ornamentally significant

Bark

  • stems are shiny and smooth
  • color of stems is bright green
  • in winter, stems can turn yellow-green

Culture

  • partial shade to shade
  • in full sun the plant grows fine, but flowers bleach out
  • needs a well-drained moist, loamy soil of reasonable fertility
  • relatively easy to grow
  • avoid over-fertilizing as this promotes too much vegetative growth and reduced flowering
  • there is a need to remove dead shoots that inevitably become apparent
  • periodic rejuvenation by cuttings plants to the ground is beneficial

Landscape Use

  • good for shady locations
  • useful for yellow flowers
  • winter interest from green stems
  • shrub border
  • foundation plant
  • useful for colonizing habit
  • as a facer plant

Liabilities

  • twig kill in severe winters down to the snow line; limits flowering
  • leaf spot
  • twig blight
  • need to remove dead shoots regularly to rejuvenate

ID Features

  • smooth, uniformly green stems
  • buds are dark and contrast with the stem stems have a zigzag pattern of growth
  • yellow, solitary flowers
  • fine, twiggy, overaching habit

Propagation

  • cuttings are easy
  • division

Cultivars/Varieties

'Golden Guinea' - This selection is notable for the large flowers (to 2" wide) that bloom for a long period.

'Kin Kan' (perhaps the same as 'Aureovittata') - The stems of this unusual form color up yellow in winter and bear thin green stripes. Other features are as per the species, and this cultivar frequently reverts.

'Picta' (probably the same as 'Variegata') - A rather demure variegated form, this leaves of this cultivar are edged with a thin white margin. It is a weaker grower (to 4' tall) and benefits from a shaded position. The flower performance is also inferior to the species.

'Pleniflora' (also listed as 'Flora Pleno') - The most common form of this species in cultivation, this plant features double, ball-shaped blooms that are an orange-yellow hue. This cultivar appears to grow larger and more gangly than the species, to 8' tall.

'Shannon' - This vigorous plant is becoming more common in specialty catalogs. It grows to 6' tall and offers larger blooms that appear earlier than the species.

© Copyright Mark H. Brand, 1997-2015.

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Citation and Acknowledgements: University of Connecticut Plant Database, http://hort.uconn.edu/plants, Mark H. Brand, Department of Plant Science and Landscape Architecture, Storrs, CT 06269-4067 USA.