Flowering in winter? It’s witch-hazel!

The witch-hazel genus (Hamamelis) consists of five species of deciduous shrubs. Three of these are native to North America, while two are native to the temperate regions of Asia. What is remarkable about these species is when they flower. The American witch-hazel, Hamamelis virginiana, which has a native range from Texas to Maine and from Minnesota to Florida, is the least unusual in this regard. It produces delicate flowers, with ribbon-like petals, beginning late fall, as other deciduous species are dropping their leaves. After pollination occurs, it takes a full year for seed maturation and dispersal.

However, like the Asian species, the other two species native to North America – the Ozark witch-hazel, Hamamelis vernalis, and the big-leaf witch-hazel, Hamamelis ovalis – both actually flower in mid-winter. The flowers of these two species are pink and red, respectively, but have the same ribbon-like petals as American witch-hazel.

IMG_4130A cultivar, known as Arnold Promise (Hamamelis x intermedia) is commonly used in ornamental plantings. It flowers so prolifically in February and March that it is often mistaken for forsythia. An interesting side-note about Arnold Promise is that it was discovered at Harvard’s Arnold Arboretum, in Jamaica Plain, Massachusetts. It is a hybrid of the Chinese and Japanese witch-hazels.

The fact that the flowers are colorful and fragrant is a clue that these witch-hazels don’t rely on wind pollination. In fact, they are pollinated by insects! Nocturnal moths — called winter moths — which can raise their body temperatures enough to allow them to be active and fly on cold winter nights, and complete the job of pollination in exchange for nectar.

There is an Arnold Promise planted outside of my lab building on Harvard’s main campus, in Cambridge, Massachusetts. With snow on the ground, and temperatures below freezing, its flowers brighten up every winter day. And, during the night, they are getting pollinated by tiny winter moths.

Amazing, isn’t it?


About Andrew Richardson

I am an Associate Professor in the Department of Organismic and Evolutionary Biology at Harvard University
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