At the end of winter, who is not desperate for flowers? Though barely three months have passed since the last autumn crocus and snowdrops faded, the lengthening days tell me that the garden is beginning to move toward spring. Dainty snowdrops are opening against the chilly breeze. Hellebores, witch hazels, and a handful of other precocious bloomers add color to the austere landscape. But what I anticipate most eagerly are the winter hazels (Corylopsis spp.). By late March, they are the very essence of springtime, their bare branches dripping with chains of primrose that glow from within. Not until April has slipped into May is the grand show over.
The 29 species of corylopsis are variations on a theme, with size the main variable. Height and spread as well as flower and foliage proportions can be very different, yet all have the deeply pleated, broadly oval to rhomboidal leaves that indicate their membership in the witch hazel family (Hamamelidaceae). In many species the emerging leaves are stained with purple to protect the tender cells from sunburn. Dense racemes of fragrant, bell-shaped yellow flowers are common to all winter hazels. Each flower cluster is hooded by pale yellow to cream bracts, which add to the floral display. A spreading habit with a zig-zag branching pattern created by the alternate leaf arrangement completes the picture. Most species produce blooms on naked stems, with leaves emerging afterwards. Autumn color comes late, in various shades of yellow.
The taxonomy of corylopsis, like that of so many other genera, is in flux. I have chosen to follow the treatment in The Flora of China, which maintains species status for most taxa. There is logic in this approach, since 20 (two-thirds of all) species are native to China. Besides, it makes it easier to discuss them.
FROM SMALL TO EXTRA-LARGE
The first species to bloom, buttercup winter hazel (Corylopsis pauciflora), is also the most delicate. Two to five flared, rich yellow flowers are carried in short racemes along thin, wiry branches. Slight in all aspects, this exceptional species creates an ethereal veil when planted en masse in open woods. Rhomboidal to heart-shaped, toothed, sea-green leaves an inch-and-a-half to three inches long emerge as the flowers fade. Mature plants are four to six feet tall and wide, with a rather flattened crown. Corylopsis pauciflora is native to Taiwan and Japan.
For pure show, select one of the larger species of corylopsis. The most widely cultivated—which will come as no surprise to anyone who knows it—is spike winter hazel (C. spicata), from Japan. Two-inch chains of rich yellow flowers with red anthers dangle from the widely spaced branches like tinsel on a bare Christmas tree. The stout, tawny stems support nearly round, two- to four-inch-wide green leaves with toothed margins. Spreading form and mounded habit make it perfect as a specimen in roomy gardens.
‘Winterthur’ is arguably the best winter hazel of all. Intermediate in size between C. pauciflora and C. spicata, it grows into a handsome plant with a spreading form six feet tall and eight feet wide, and sometimes larger. ‘Winterthur’ produces profuse showy racemes nearly two inches long. The hybrid gains its excellent fragrance from spike winter hazel, while its fine texture and dense branching originate in its buttercup winter hazel parent. ‘Winterthur’ foliage is rounded and attractive, a rich green in summer and turning a clear yellow in autumn.
Distinguishing C. sinensis from C. veitchiana may be a game for specialists. The Flora of China notes that while the stamens of the former are shorter than the petals and the undersides of the leaves are pubescent, those of the latter are hairless and the stamens protrude beyond its primrose-yellow petals. Chinese winter hazel (C. sinensis) is a tall, wide shrub (or small tree) up to 12 feet high. Give it plenty of space or use it as a vertical bridge between the floor of the garden and the tree canopy. Veitch's winter hazel (C. veitchiana) has a more refined appearance and grows only six to eight feet tall and wide. Added value comes from the pleated, narrow oval, toothed leaves, which emerge decoratively rimmed in burnt umber. Try a group of three as a focal point or airy screen.
Larger and more dramatic than either of these is fragrant winter hazel (C. glabrescens; syn. C. gotoana). Reaching 10 to 15 feet in height and spread (though growth to over 20 feet has been reported), a mature specimen laden with golden flower clusters is a stunning sight. The sweetly scented one-and-a-half-inch racemes of widely flared flowers open in early April. Foliage is broadly oval, and has toothed margins and an elongated, pinched tip. Cultivar ‘Longwood Chimes’ has exceptional flowers. This hardy species from northern Japan will appeal to gardeners in Zones 5 to 8.
Another large species with an upright rather than spreading form is C. platypetala. Though The Flora of China gives a height of just 6 to 8 feet, this shrub or small tree reportedly can reach 12 to 18 feet, with a spread of 10 feet. The upright vase shape is spangled with two-inch chains of wide-petaled, nicely fragrant flowers in spring, and rounded, blue-green leaves with scalloped margins in summer. (It is also listed as C. sinensis var. calvescens.)
The size prize among corylopsis goes to C. willmottiae, another Chinese species that easily reaches 15 feet, and often surpasses 20. This giant must be reserved for big gardens, where it can be breathtaking. Its ample chartreuse flowers are fragrant and outfacing, while its toothed, rounded leaves are four inches long and widest at the tip. The cultivar ‘Spring Purple’ has rich, plum-colored spring growth that turns to green as the season wears on.
In my garden, corylopsis escort winter to the threshold of spring. Early in the season, branch and bark are the main event. When the first flowers clothe these fragile bones, luminescence becomes a key element in the alchemy of the season. Place your plants to take full advantage of the low sun angles.
But corylopsis can bring beauty to every season. Layer your plantings for cumulative dramatic effect. Contrast a winter hazel with a rich evergreen backdrop, then lay before it a flowering carpet of wildflowers scattered among sweet box (Sarcococca hookeriana var. humilis), wild ginger (Asarum europaeum), and holly ferns (Polystichum spp.). Mixed heaths (Erica spp.) and heathers (Calluna spp.) offer colorful evergreen foliage and early flowers. An under-planting of hellebores, species crocus, cyclamen, and miniature daffodils (Narcissus spp.) will play splendidly off winter hazel in the earliest spring.
A few weeks later, my beds feature trilliums and epimediums to carry the flowering season. After flowers fade and bulb foliage disappears, ferns contrast with deep green hellebore foliage beneath corylopsis now laden with lush leaves. For summer color, lace the wiry stems of vines like clematis through the shrubs’ crowns. Fall color comes from bugbanes and Tricyrtis, joined by the floriferous autumn cyclamen (Cyclamen hederifolium) and, finally, the yellowing foliage of winter hazel itself.
Corylopsis are forest plants, found in open woods, clearings, and on mountain slopes throughout temperate Asia. Give them fertile, well-drained acidic soil in full sun to partial shade. Too much shade and they will be shy to bloom; too much hot sun and the leaves may toast. Avoid hot, windy sites, too. Established plants tolerate moderate drought, but these are not plants for arduous conditions and poor soil. I prefer planting balled-and-burlapped stock to minimize root disturbance and soil incompatibility, but small containerized plants establish quickly. Pests are few, though Japanese beetles may munch the leaves. Of greater concern are late frosts, which may kill emerging flowers or crisp the young leaves. Permanent damage is seldom an issue, but extreme cold can spoil the show for the year.