Posted by: tysonrc | March 26, 2010

Natural Calendar

Many of us agree that it is currently the end of the month of March.  Spring began on March 22.  These seem like rock-solid facts.  The natural world goes on a different sort of calendar though.  This calendar is called Phenology, and it is the natural progression of changes in the environment; such as migrating birds or spawning fish. 

first sighting 3/16/2007

Even though the word phenology is not one that is heard too frequently, the idea permeates many facets of life.  Ever heard “corn should be knee-high by the fourth of July” or “morels are up when oak leaves are the size of mouse ears”? 

The natural world is not dictated by our idea of a calendar.   This is what guides a great deal of research here at Tyson Research Center and it is also why planning a vacation in spring or summer can be next to impossible for a field ecologist.  One early warm up and the frogs start breeding, pollinators start flying, and snakes come out of their den.  No one can accurately predict when that first warm up will occur using our calendar, although many try.

Many outdoorspeople have become very attuned to phenology. 

first sighting 4/2/2008

 They know that when dogwoods are blooming, crappie are probably spawning and, therefore, easy to catch almost anywhere within their range.  In northern Arkansas this might be march 25, but in northern Missouri it is closer to early may, either way the dogwoods bloom and the crappie spawn.  If you time it right, you can drive north in spring a few hours and watch the phenological clock tick backwards as you travel back in time, seemingly.  This is helpful if you missed the serviceberry blooms or trillium flowers in given year because you can just drive back in time and go see them.

Websites exist to watch spring spread out like a fan across much of the nation as well as participate in it.  The USA Phenological Network ( is one of these sites.  They encourage you to join them in the observance of the seasons and report back, via the website, about what is happening where. 

first sighting 3/13/2009

This can be a very enjoyable activity or just used as an excuse to get some outside time.  You can also keep a personal journal of what activity is first noticed on what date.   A journal of blooming flowers, or spring peepers calling might seem like a trivial thing, but these can be extremely important data sets for future use and the more detail you keep the better.

The photos in this post show spring beauties through the last four years.  They were all taken in the same spot, about 20 meters square, where they usually come up fairly early on Tyson Research Center.  They all appear to be right around the same time, except for the anomaly of 2008.  I’m  Still not sure why they came up so late in that location that year, they were already blooming in several other locations, just not there.  That is what can make phenology so fun, it always leaves you with many things to ponder on….

–Travis Mohrman



  1. While not about phenology, I began my post on the same day with a phenological theme – interesting how naturalists think alike!

  2. What a nicely written post, Travis! I like your yearly Claytonia photos too.
    I recently learned another phenological reference: “plant your corn when maple leaves are the size of squirrel ears.” According to that, I’m behind in planting.

  3. whew, at least it wasn’t phrenology. in geology we talk about phenocrysts, and of course the same root is behind phenomenology. cool article. not seasonal, but related to poison oak and ivy, the phrase is “leaves of three, leave it be.”

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