Sun-Diet for Plants?

Harebells were the first plant
to bloom this summer, and the last
plant to bloom this fall.

Plants are shutting down now, as we approach the end of the growing season.  Thanks to the uncharacteristically warm weather in Laramie the past couple of weeks, grasses are still holding their seeds and harebells, which are the most persistent and stubborn bloomers I've ever seen (I'm half-way convinced they'll still bloom in the dead of winter), are still pushing out new flowers.

Sun-Hungry Plants?

But here's a little food for thought, now that we've moved from the season of greens to the season of oranges and reds.  The Berry Prairie is sandwiched between the Geology building (to the east, or the left in the picture below) and the Berry Center to the west.  With our shorter days, enhanced by the shade from these buildings, the Berry Prairie receives full sunlight from approximately 11:00am to 3:30pm - and it'll be this way in the spring too.  In comparison, plants that are on the actual prairies outside of Laramie receive full sun from about 6:30am to 7:00pm this time of year.  Horticulturalists define "full sun" as 6 hours of direct sunlight, which the Berry Prairie currently doesn't receive.

At the end of June, the green roof was entirely sunny at 9:30am.

In the beginning of October, the green roof is entirely shaded at 9:30am.

So what will happen to the plants on the green roof, which have evolved to soak up twice the insolation they currently get?  It's like the plants are on a sun-diet, the vegetative version of Atkins.  Will they notice the reduction in this vital resource?  How could they not?  How will they react as a result?  

Any guesses?

Written by Brenna Wanous, Berry Center