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The Science of Springtime

April 6, 2020

Dr. David Galbraith (Head of Science, Royal Botanical Gardens)

We enjoy a great variety of weather in Canada, which perhaps is why talking about it is so popular as a past-time. That variety springs from a wide array of conditions, including the inclination of the earth’s rotational axis that gives rise to the seasons themselves.

Plants have evolved many coping mechanisms to deal with seasonal change, nearly all of which we can see at work in southern Ontario. For plants that lose their leaves in the fall (an adaptation to conserve water and deal with the fact that ice and cell walls do not mix), spring often starts with the dramatic unfurling of new foliage. Nearly all vascular, or higher, plants survive through the winter on stored energy, and with new leaves comes the capacity to capture new solar energy and refill stores.

Quite a few plants also begin their annual reproductive cycle with the setting of flowers pretty early. Some, such as American Witch-hazel (Hamamelis virginiana) actually flower in winter. Our Herbarium Volunteer Dean Gugler saw 14 Witch-hazel cultivars in bloom at RBG on February 24 this year. Eastern Skunk Cabbage (Symplocarpus foetidus) is so enthusiastic about flowering that it doesn’t even wait for the snow to melt. This amazing plant generates its own internal heat, sometimes as much as 35°C above air temperature, in order to expose its flowers to pollinating bees and flies. Dean also saw Skunk-cabbage blooming in Grindstone Creek valley in February.

Biologists like to observe the natural cycles and timing of events in nature, a study called phenology. Dean has been recording flowering dates of a wide variety of plants at RBG for many years.

Recording the dates of flowering of plants may not seem to be too exciting; it’s hardly high-tech science. All you need to do it is knowledge of plant identification and a calendar. However, this kind of information is turning out
to be critical for our understanding of climate change. First Flowering Date, or FFD, has been shown in numerous studies to be very sensitive to temperature change.

Phenology is also a wonderful way everyone can contribute to understanding climate. It is one of the key ways that “citizen scientists” are aiding in the understanding of our world. Whole networks of phenology recorders regularly submit their findings to Plant Watch, and you can too! There are lots of resources on their web site, and a how-to-guide for budding scientists. More than the timing of plant events can be recorded too: even things like the dates that ice thaws on rivers or lakes can be important observations.

Not all plants respond the same way to changes in temperature. In a study of flowering times in Alberta in 2011, botanists Elizabeth Beaubien and Andreas Hamann(1) found that early-flowering plants bloomed about two weeks earlier in the last decade than they did in the 1930s, while later-flowering plants were only between 0 and 6 days earlier over the same span.

Such observations of phenology are showing that plants are flowering earlier now in North American and Europe than in historic times. This in turn has consequences for other organisms, such as bees or other insects that may
depend on specific flowers for pollen.

Having studied various books on flowers and noting when they bloomed, Dean started to make his own records. When asked what he’s found himself, he wrote:

“Over the years I have found that the flowers do not read the books and often bloom much earlier and later than expected. Violets usually bloom in the early spring but I have found blooms in December. In addition, as the years have passed and the winters have become warmer, I have found more and more flowers blooming later and later and starting earlier too.”


  1. Beaubien and Hamann, 2011. BioScience, 61 (7): 514–524.

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