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Mild Winter, Early Blooms, Northern Hemisphere

By Jessica B. Turner

Spring has sprung in early January, only weeks away from the 2015 winter solstice.  Around the Northern hemisphere, flower buds have been bursting open, even though we have many months before the last threat of frost will disappear.  Magnolia blooms have been spotted in Belgium at the Arboretum Wespelaar, in Kentucky at the Boone County Arboretum, and in Pennsylvania at the Morris Arboretum in Philadelphia.  In the Polly Hill Arboretum outside of Martha’s Vineyard, Ozark Witch Hazel shrubs are showing their beautiful red and yellow blooms.  The Bernheim Arboretum and research forest in Kentucky has documented blooming Autumnalis Cherry, Chinese Lilac, Forsythia, and Magnolia Hybrids.  At Harvard’s Arnold Arboretum, the Korean Rhododendron are in full bloom, despite the fact these usually bloom in April.  What will our spring look like if trees are flowering in winter?


The tax for enjoying a warmer winter may be a less vibrant spring.  Trees are cued to sprout leaves, buds, or blooms by a combination of natural events, such as an increase of air temperature (Chmielewski & Rötzer, 2001), or the length of time since the last freeze (Bailey & Harrington, 2006).  A milder winter and a warming climate can make some tree species more vulnerable to frost damage (Cannell & Smith, 1986; Hänninen, 1991).  This is because buds and flowers can be the most susceptible part of a tree to freezing temperatures (Salazar-Gutierrez et al., 2016).  A frost can decimate newly emerged flowers or buds, which might reduce the number of buds that will bloom in spring.  Further, any flowers destroyed by frost can mean a reduced fruit production (Rodrigo, 2000).  Spring may look different this year, but hopefully, next winter will be more familiar.  Just like humans, some trees need a period of rest or dormancy.  


Further Readings:




Bailey, J. D., Harrington, C. A. (2006). Temperature regulation of bud-burst phenology within and among years in a young Douglas-fir (Pseudotsuga menziesii) plantation in western Washington, USA. Tree Physiology, 26: 421-430.


Cannell, M. G. R., & Smith, R. I.. (1986). Climatic Warming, Spring Budburst and Forest Damage on Trees. Journal of Applied Ecology, 23(1), 177–191.


Chmielewski, F. M., & Rötzer, T. (2001). Response of tree phenology to climate change across Europe. Agriculture and Forest Meteorology, 108: 101-112.


Hänninen, H. (1991). Does climatic warming increase the risk of frost damage in northern trees?. Plant, Cell & Environment, 14: 449–454.


Rodrigo, J. (2000). Spring frost in deciduous fruit trees morphological damage and

flower hardiness.Scientia Horticulturae, 85: 155–173.

Salazar-Gutiérrez, M. H., Chaves, B., & Hoogenboom, G. 2016. Freezing tolerance of apple flower buds, Scientia Horticulturae, 198: 344-351.

Thursday, January 21, 2016