Monday, December 3, 2012

Waiting for winter in the Rockies

Nice mixture of new and old strawberry leaves, a result of extraordinary
warm temperatures in Colorado this fall
Wild weather makes for interesting phenology observations. Always something new to learn or discover this way.  The other day I read a comment about nothing should be happening here now since it is 5,000' elevation and December in the Rockies. But every time such a statement is made there inevitably arises an exception. Today I saw that exception in the form of new flowers emerging on a pennycress plant (Thlaspi arvensis), a small white mustard species. All around the garden and along my walks you can see plants responding to our strange weather which today for example gave us 60 degrees and no sign of snow. How can this be?  Plants should be smarter than to put out new flowers or foliage this time of year when it may snow or freeze at any time!

Pennycress with new flowers on December 3th, growing in my patio
While most plants must go through a cold period or dormancy usually for a month or more before they will respond to signals of a coming growing season, some plants can and do send out new leaves or flowers whenever it is warm and wet enough to do so.  Some like this pennycress I saw today are sometimes called winter annuals. This just means that they do not live for more than one year and can start growing in the winter if it is warm enough - it doesn't really matter what time of year or how much sunlight is available. While many weeds such as dandelion, pennycress, knapweed and others can do this, even native wildflowers can do this as well. In much of the interior West, for example, the early native wildflower, sagebrush buttercup (Ranunculus glaberrimus) can also begin to flower anytime in the winter. It has been recorded flowering in December and January in Montana, although March is a more typical first time for flowers.

Around my house today I could see new leaves of the bulb grape hyacinth or Muscari, new leaves from a parsley plant (and many other herbs), new leaves of the Project BudBurst species yarrow (Achillea millefolium), new strawberry leaves, and of course lots of green lawn grass (Poa pratensis). The great irony is that with the unprecedented hot dry summer many lawns were brown during the summer, but have turned a deep green this fall and winter, now that there is a little more moisture and cool but not cold temperatures.  These are cool season grasses, so when daytime temperatures are 10 or twenty degrees above normal it is well within the range of activity for these grasses.

yarrow with new leaves (Achillea millefolium)
So December is a good time to review your notes from the year, submit those phenology observations that you have not yet had a chance to go through. But it is always a good idea to still make regular trips outdoors and see what is going on. Chances are that you will discover something new or surprising out there. And if you have a chance to travel to California or the Gulf coast there is even more to observe out there. Let us know what you find.

Paul Alaback

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