Friday, March 19, 2010

Kerria japonica

Kerria japonica is the one and only member of the Kerria family. Native to the mountains of northwest China and Japan, the Japanese Kerria reaches up to 10 x 14 feet. Fast growing, bushy, graceful and arching; the fastest recorded rate is 8 feet per year.
The toothed oval leaves are simple and alternatively spaced and appear early in spring. They have prominent veins and are up to 4 rarely 6 inches long. They are dark green above and downy below and turn to yellow late in autumn.
The deep yellow flowers, up to 2 inches wide, are borne early to late spring in axilliary and terminal spurs.
Stems are light green and very attractive. The green stems looks especially good during winter when planted with white barked trees.
The species has single flowers though the double form is much more common in cultivation.
Prefers a cool moist climate; the Kerria grows well in full sun to partial shade in any well drained, moderately fertile soil. Tolerant of full shade as well as heavy clay but not summer drought. Propagation is easy from either soft tip cuttings taken in spring or half hardened cuttings taken in summer which root easily. The stems can also be layered. Can also be grown from suckers in autumn.
Exremely clay tolerant and hardy zones 4 to 8 in sun or partial shade, growing well in both the north and the Deep South. The flower buds are killed at -20 F however the stems can tolerate colder temperatures. In zone 4, branch death can occur during severe winters, however plants usually recover quickly during spring after freeze damaged wood is pruned off. Tolerates drought and dry shade. Deer resistant, insect pests generally do not exist and disease problems are minor.

* photos taken on Aug 2 2012 in Bayfield, Ontario

* photos taken on June 23 2013 @ U.S. National Arboretum, D.C.

* photos taken on Aug 4 2013 in Bayfield, Ontario

* photos taken on May 7 2014 @ London Town Gardens, Edgewater, MD

* photo taken @ Smithsonian Inst, Wash., DC on Aug 25 2014

* photo of unknown internet source


'Albiflora'
Vase-shaped, reaching up to 8 x 8 feet, forming a thicket of green stems.
The abundant, single, white flowers are borne during mid spring, repeating sporadically all summer long.

'Geisha'
Reaches a maximum size of 8 x 8 feet ( 3.3 feet in 1 year; 5 x 6 feet in 10 years ), with green stems that bear very double, bright orange flowers. The foliage is mid-green and splashed with yellow.

'Golden Guinea'
Reaches up to 8 x 8 feet. The large, single, golden-yellow flowers up to 2 inches across are borne in abundance over a long period of time. They are borne profusely during mid-spring but often repeat bloom during the summer.

* photos taken on Apr 24 2016 @ U.S. National Arboretum, DC


'Honshu'
Reaching a maximum size of 8 feet ( 6 feet in 10 years ), this repeat bloomer bears golden-yellow flowers, over 2 inches across. The flowers are the largest of any Kerria.
The stems are bright green.

'Kin-Kan'
Reaches up to 6 x 8 feet, forming a thicket of stems that are bright yellow all year.
Foliage turns a good yellow autumn color.
The single, orange-yellow flowers, up to 1 inch across, are borne during spring then repeating sporadically all summer long.

'Picta'
Elegant and attractive, reaching up to 6 x 8 ( rarely over 5 x 5 ) feet, with gray-green foliage that is boldly edged with creamy-white. Some records include: 3 years - 5.2 feet.
The abundant, golden-yellow, single flowers are borne during spring, then repeating during summer.

* photo taken on June 1 2014 @ Maryland Horticulturalist Society garden tour, Clarksville

* photo taken on Nov 19 2016 @ London Town Gardens, Edgewater, MD

'Pleniflora'
Very fast and larger growing to 12 x 14 feet with double golden yellow flowers up to 2 inches wide.
Some records include: 5 years - 5 x 8 feet.

* photo taken in Clarksville, MD on April 2008

* photos taken on Aug 1 2013 in Stratford, Ontario

* historical archive photo


'Shannon'
A larger more vigorous plant than the species, growing up to 10 feet. Leafs out earlier and flowers earlier with larger flowers than the species.
The flowers are single and yellow.

* photo taken on April 9 2010 in Howard County, MD

* photos taken on Apr 18 2017 in Howard Co., MD

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