“Vernalis only requires a month’s worth of chilling,” Mr. Del Tredici said. “That’s long enough for this species. The days are getting longer. And it takes advantage of insects that hatch with the first warm weather.”  Other witch hazels, like the Chinese and Japanese species and their hybrids, have longer chilling requirements, so these bloom in February or March.  Until that day at the Clark garden I thought of witch hazel as the stuff my mother kept in the medicine cabinet — Dickinson’s Witch Hazel — for soothing cuts and bruises, aching backs and feverish skin.  And, in fact, according to “Witch Hazels,” by Chris Lane, the astringent is made from the distilled pulp of the American native, Hamamelis virginiana, which blooms in the fall. (The flowers are usually masked by the glorious yellow foliage, but a new selection, Harvest Moon, blooms after its leaves drop.)  Mr. Lane, the owner of Witch Hazel Nursery (witchhazelnursery.com) in Kent, England, where he tends a collection of about 250 specimens, has compiled all the known species and varieties into what is now considered the witch hazel bible, complete with color photographs.  According to Mr. Lane, the colonists learned of witch hazel’s medicinal value from the Indians, who boiled its twigs and branches for a salve for irritated skin and eyes, as well as a drink to cure colds and kidney ailments. It was first commercially manufactured in 1866 by Thomas Newton Dickinson, who built a distillery in Essex, Conn.  But back to the garden. The witch hazels that enchant this time of year are H. mollis, the Chinese species; its many cultivars; and hybrids of the Chinese and the Japanese species (H. japonica), which range in color from pale yellow to gold, orange and red.  Some grow upright, like Arnold Promise, a natural cross that occurred between the Japanese and Chinese species when they were closely planted at the Arnold Arboretum. Introduced in 1963, Arnold Promise has proved a workhorse, with its vase shape, fragrant gold flowers and fabulous fall color — yellow, orange and red — with a gold margin around each leaf.  But Arnold is a bit stiff for my taste. And it is also subject to leaf blight in hot, humid climates.  I am still partial to H. mollis, the straight Chinese species, with its clear yellow fragrant petals and its wide, spreading habit. Mollis hybrids are beautiful, too, especially Kort’s Yellow, a fragrant sulphur yellow, and Wisley Supreme, a light yellow.  The best places to observe the diversity of witch hazels are public gardens. Cultivars of the grand old mollis species are blooming at the New York Botanical Garden (nybg.org) now, and a spectacular hybrid, Barmstedt Gold, which has sweet-smelling golden yellow petals, will bloom, depending on the weather, in late February or early March, in the fragrance garden on the north side of the conservatory.  Arnold Promise has just started to bloom at the Brooklyn Botanic Garden, but Jelena, whose copper orange flowers have been going strong for a month, is at its ebb.  “Jelena makes a terrific cut branch, if you bring it inside,” said Patrick Cullina, Brooklyn Botanic Garden’s vice president for horticulture. “A simple cutting allows you to examine the complexity of those strappy petals suffused with red and orange and a little gold.”  The problem is, Jelena (pronounced YELL-eh-nuh) comes up a big fat zero for scent. I know, because I buried my nose in its crinkled apricot flowers about two weeks ago at Green Spring Gardens, a public garden in Alexandria, Va., which has 79 different witch hazels.  Jelena was just about the most beautiful bloomer I saw that day, backlighted by the sun, glowing on the edge of a long border, beneath tall pines. “Siting makes all the difference,” said Brenda Skarphol, a horticulturist at Green Spring who keeps careful records on each of these plants. She pointed out how dark bloomers, like Birgit, a red purple, and Feuerzauber, a coppery red, tend to fade into the landscape.  “So plant these next to some yellow ones,” she said. “Or out in the open, against the blue sky.”  We saw some gorgeous fragrant hybrids that day: Aurora, whose long yellow petals are tinted red at the base; Angelly, a clear light yellow.  Ms. Skarphol’s favorite mollis types include Early Bright, which has a fragrant golden yellow flower, tinted red at the base; Kort’s Yellow, a very fragrant sulphur yellow; and Wisley Supreme, a light yellow with a sharp, almost astringent scent. The mollis types turn yellow or gold in the fall; H. vernalis, the Ozark witch hazel, turns yellow-orange, then crimson in fall.  For pot culture, Chris Strand, a witch hazel expert who assembled the Green Spring collection before he moved on to direct the gardens at Winterthur, near Wilmington, Del., recommends Sunburst, a chartreuse yellow hybrid, and Princeton Gold, a sulphur yellow mollis type.  Although there is a notion that witch hazels are too rangy and big to fit in the small garden, Mr. Lane explains how these shrubs, if properly pruned, can be grown for years in large containers and small borders. The key, he writes, is pruning them the second year after planting, as soon as they finish flowering: “Prune all the previous season’s growth back to two buds.” And do the same thing every year.  A version of this article appears in print on , on Page F7 of the New York edition with the headline: Winter’s Cheerleader, Yelling for Spring. Order Reprints| Today's Paper|Subscribe
Witch hazels light up a gray wall, the bare woods or even a pot on a terrace, long before anything else is in bloom.