Kerria deserves a Second Look

Kerria japonica, The Japanese Yellow Rose, has been around for a long time. It has been sold for years, most commonly by low end mail order companies. For whatever reason, wholesale growers and garden centers rarely include this plant in their mix, and I wonder why? The more I see of this plant and what it can do in the landscape, the more I feel it deserves a second look. Please join me.

Kerria japonica is a hardy (Zone 5) deciduous shrub that matures at 3 to 5 feet in height. It's a dense mounded plant with numerous slender, zig-zagging branches that emerge at ground level. The beauty of Kerria is found in its flowers, stems and foliage. The bright yellow flowers are noticeable reminiscent of an old fashioned rose with its 5 petals. The flowers clearly make this plant a member of the Rosaceae family. In early spring, before the leaves emerge, the numerous yellow flowers create a colorful show. As an added benefit, Kerria will often rebloom off and on all summer long. The effect is beautiful and rewarding. Kerria is also blessed with attractive ornamental stems. From autumn to spring, its bright kelly green stems create a wonderful, fresh impression. Having visited the Cincinnati Zoo and Botanical Gardens in early spring a few years back, I distinctly remember big green drifts of Kerria. I was surprised and delighted to see it used throughout their beautifully landscaped grounds. Around every corner we were greeted by a mass of bright green. This unique combination of color and zigzagged lines creates a lasting impression.

You also have to appreciate the clean and simple foliage of Kerria. The leaves appear birch-like at first glance with its narrow triangular shape, but unlike birch, its leaves are brighter, doubly serrated, and display a pronounced puckering between the leaf veins. Always clean and green the foliage is a distinctive asset.

Culture

This is not a fussy plant that is difficult to grow or manage. Quite the contrary, Kerria is happy in most any reasonable well drained soil. It requires little fertility, and seems to flower best if neglected. Unlike other members of the rose family, Kerria has no serious insect of disease problems. The remarkable thing about this is that it thrives when grown in partially shaded to fully shaded locations. Few plants flower this well in shade! Full sun is also an option, but it does present a few problems. The flowers do not hold up as well and it can show some stem die-back if exposed to winter sun. Neither of these problems are severe, but both can distract from the beauty of the plant. It should be noted that this plant dislikes heavy, poorly drained soil. It will languish and grow smaller by the year. As far as ongoing maintenance, I personally feel this plant benefits from an occasional hard pruning. Cutting the plant to the ground produce a fuller plant, brighter stems and improved flowering.

The Cultivars

The most popular cultivar of Kerria is the old fashioned double flowered form, Kerria j. 'Pleniflora'. Its yellow button-like flowers resembles a chrysanthemum, and at peak bloom they polka dot the plant to create a distinct look. Kerria 'Pleniflora is not one of my favorite plants. To me it looks too contrived. I much prefer the simplicity of the single flowered forms. Two of the best single flowered cultivars are 'Honshu' and 'Golden Guinea'. I can detect only slight and inconsequential differences between these two plants. Both were selected for their large single flowers. If I had to choose only one of them I would pick ‘Honshu’ because its flowers are slightly larger and they have a soft and pleasing fragrance. The plant was introduced by Dr. Clifford Parks of Camellia Forest Nursery in Chapel Hill. Many people choose 'Golden Guinea' strictly because of its name. The name properly describes the size and color of the bloom. No the name Guinea does not refer to a bird or some exotic country, it refers to a large gold coin.

For those of you who need even more excitement in your life, several variegated selections are available. The best variegated type is called Kerria japonica 'Picta'. Not a great name, but a very good plant. Its leaves are graced with a creamy white margin that is not at all offensive like some variegated plants. The overall effect is very nice, and a decent specimen garners much attention. It does have its shortcomings. It can be slow growing when young making it difficult to produce especially when compared to the species. It also has a tendency to throw an occasional green shoot, which must be removed. This is a simple task and most gardeners would gladly pay this price to have such an interesting plant. I have seen another variegated clone under the name of 'Kinkan' or 'Auro-vittata'. This is worthless selection best left to the most ardent collector or relegated to the botanic garden. This "beauty" has green and yellow striped stems that tend to revert at the speed of sound and has small single yellow flowers.

While all Kerria selections have yellow flowers; the cultivar ‘Albaflora’ has blooms that are a near white, butter yellow. The color is more subtle, and I my opinion more pleasing to the eye than the typical bright yellow of the species.

Kerria is a beautiful plant with year long interest. Plant it in mass in a shady location and I think you'll be pleasantly surprised how nicely this plant performs. Very few flowering shrubs perform so well in the shade and you'll love the winter effect provided by its bright green stems.