Leaf out across four countries

Posted by Libby Ellwood

While it’s no secret that plants leaf out earlier when it’s warmer, there’s still a lot to learn about how leaf out differs among species and location. Leaf out signifies the beginning of the growing season, and is influenced by climate change, so it is important that we take a broad view in studying it. 

Acer japonicum, Japanese maple, leafs out early each spring.
Photo credit R. Primack

In a recent paper, researchers from eight botanical gardens examined leaf out in 1600 woody plant species. Over 2011 and 2012 we found spring leaf out differed by three months. We saw that angiosperms leafed out before gymnosperms, deciduous species before evergreen species, and shrubs before trees. Certain physiological differences among species, such as vessel size and arrangement, also affect leaf out.

Rhodendron fargesii leafs out later in the spring.
Photo credit R. Primack

Even though the botanical gardens were in four different countries, US, Canada, Germany and China, species leafed out in the same order. This demonstrates that species that are early to leaf out in North America are also leafing out early in Europe and Asia. As species ranges shift and forest composition is altered due to climate change, our understanding of leaf out phenology will grow increasingly important. Read more about it in the full article:

Panchen, Z. A., Primack, R. B., Nordt, B., Ellwood, E. R., Stevens, A.-D., Renner, S. S., Willis, C. G., Fahey, R., Whittemore, A., Du, Y. and Davis, C. C. (2014), Leaf out times of temperate woody plants are related to phylogeny, deciduousness, growth habit and wood anatomy. New Phytologist, 203: 1208–1219. doi: 10.1111/nph.12892