In the Garden: A Couple of Rose Relatives

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Kerria flower

Everyone is familiar with roses—the genus Rosa, with over one hundred species and countless varieties—even non-gardeners.  But they’re many other members of the Rose family (the Rosaceae) that are not well-known, and unlike roses, some even grow well in the shade.

With its bright yellow blooms, Japanese Kerria (Kerria japonica) puts on a good show in April. Kerria typically goes simply by that name, partly because it’s the only member of this genus, and also because it’s short and easy to pronounce. One source lists Japanese Rose as an alternative name, and this moniker might appeal to some plant shoppers who are more comfortable with the name “rose.”

Native to the major islands of Japan, as well as parts of China, Kerrias are small-to-medium-sized shrubs, generally topping out at less than six feet in height and with an equal spread. Given their tendency to sucker, their ultimate width could politely be listed as “indeterminate”; the pass-along Kerria in my own yard is the result of such spreading in a friend’s garden. The lesson here: if your Kerria eventually gets out of bounds, dig up the unwanted stems and share them with friends. Sort of a horticultural pyramid scheme: once the market is saturated, someone may try to give some back to you.

Leaves on Kerrias are small, toothed and refined, bright green, and with a superficial resemblance to birch foliage. Occasionally they may put on soft lemon-yellow color in the fall. Flowers on the straight species are 1” to 1 ¾” across, five-petaled and golden yellow. Borne in profusion in early spring, they may also continue sporadically throughout the growing season.

Much of Kerria’s ornamental appeal comes from its stems. Slender, supple and zig-zag, they remain green throughout the winter, adding off-season brightness to the winter garden. As the plant ages, the older stems will die and turn brown. Not a big deal; just snip the offenders off at ground level.

Several cultivars of Kerria are available. Perhaps most commonly seen is ‘Pleniflora’, aka ‘Flora Pleno’, with nearly ball-shaped double flowers. The flowers tend to be longer lasting than on the species, while the plant itself is more erect and lanky, commonly growing six to eight feet in height.  If you’re fond of variegated plants, ‘Picta’ has soft gray-green leaves with white margins among single yellow flowers. This plant tends to revert, so any branches without variegation must be pruned out.  Some authors specifically mention ‘Aureovittata’ and ‘Kin Kan’ as cultivars to avoid.  Their branches are striped green and yellow, a nice effect, but they quickly revert to the usual green.

‘Honshu’ (and the similar ‘Golden Guinea’) have somewhat larger flowers than the species and appear over a longer period; foliage is a rich green. ‘Honshu’s flowers are also pleasingly fragrant. If you prefer creamy yellow flowers, try ‘Albescens,’ sometimes listed as ‘Albiflora.’

Moist, well-drained soil is ideal for Kerrias, although they will do fine with just average moisture.  Partial shade or morning sun is ideal. Too much sun bleaches the flowers, and too little sun will lead to reduced flowering. Excess fertilizer will produce rampant growth; compost is ideal. If your plant gets too tall or rangy, cut it back after flowering to about a foot, and it will re-grow to about 3’ to 4’ by next fall. Otherwise, prune out any dead stems, and remove unwanted suckers to contain growth.  one source listed Kerria as deer-resistant, but you never know.

If you’re willing to go to the gourmet plant catalogs and search for a rarity, you might be able to find Kerria’s American cousin, also a member of the rose family. Alabama Snow-wreath (Neviusia alabamensis) occurs on limestone woodlands in scattered locations across Alabama, Georgia, Tennessee, Mississippi, and Arkansas. Botanists have not observed plants setting seed, so all reproduction may be asexual. A lack of genetic diversity makes Neviusia susceptible to extinction if it were to be affected by climate change, development, or disease.

Alabama Snow-wreath. Photo: Kurt Stüber/Wikipedia.

A small mounded shrub, Snow-wreath tops out at 3’ to 6’, with a similar spread. Like Kerria, it can spread by suckers and form a colony. Its leaves also resemble those of birches, and the stems are somewhat zig-zag. The small white flowers lack petals, but the abundant stamens create a feathery appearance— a wreath of snow.

Alabama snow-wreath prefers well-drained soil—doesn’t that apply to so many plants?!—but accepts average garden conditions. Either full sun or partial shade is okay. Any pruning should be done immediately after flowering to avoid losing next year’s blooms.

You won’t find Snow-wreath at the average garden center, let alone the big-box stores. In fact, in a quick search I found it only at Nearly Native Nursery in Fayetteville, Georgia. You may have better luck and might see it at native plant sales or at botanical garden events. Impressive when in bloom, it tends to blend into the landscape at other times. In any season, Alabama Snow-wreath remains a good plant for stumping your gardening friends. 

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