Backyard Biodiversity January 2021 Winter Blooms

What blooms in the middle of winter? Witch-hazel!
 
Witch-hazels are a group of winter flowering shrubs with 3 species (Hamamelis virginiana, H. vernalis and H. ovalis) native to the North America and 2 species native to parts of Asia. Witch-hazels are small trees or shrubs generally only growing to 10 -25 feet tall. American witch-hazel, Hamamelis virginiana, blooms from September through December, whereas the other species, including the Ozark witch-hazel (H. vernalis) bloom from January through March.

Witch-hazel flowers are small but showy, with colors ranging from yellows, oranges and reds. They have thin, ribbon shaped petals. Witch-hazels flower after all their leaves have dropped, and so, even though the flowers are small, the flowers can be readily seen against a barren winter landscape. The pictures I post are of the Ozark witch-hazel that I planted in my backyard.

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 Given this seemingly strange trait of blooming when most pollinators are gone or hibernating, the question arises, what pollinates witch-hazel?

Bees and flies have been observed visiting witch-hazel but more likely in the warmer portion of their blooming period. The flowers are sweet smelling and contain nectar, which is used to attract pollinators, so it is unlikely that they pollinate via wind. One possibility might be a group of Noctuid moths known as owlet moths. The brown rather non-descript moths were studied by Bernd Heinrich who observed them feeding off of witch-hazel flowers in the winter. These moths are known for vibrating their wings (or shivering) to increase their body temperature, allowing them to be active in cold weather. This trait of shivering to increase their body temperature is not unique to this group, many other moths and butterflies are known to shiver. What is interesting is that they can initiate shivering a temperature much colder than other Lepidoptera (moths or butterflies).

In the winter these moths seek shelter under leaf litter, which is considerably warmer than winter air temperatures, and if it snows, the snow adds an additional layer of insulation. The moths also have an insulating layer of fur (actually modified scales). Heinrich also found that they only need to warm up and their thorax (the body part that contains the wings) and not their abdomen during flight. They can maintain a large difference in body temperature between the two main body parts. (Check out Bernd’s paper to see his cool experiments here: https://www.jstor.org/stable/24979345 ).

 ​One more cool thing about with-hazels is that their seeds are in long capsules, as the pods dry they explode open, shooting the seeds up to 30 feet away from the parent tree. Seed dispersal is fascinating….check out this video with David Attenborough to learn more about the cool adaptations plants have to ensure their seeds get a good start in life.