Photo of the Week – February 25, 2016

After a long week in Texas, it was nice to spend a restful afternoon at our family prairie last Saturday.  The weather was gorgeous and we spent a great day playing with the dogs, cooking hot dogs on a campfire, cutting small cedars, hiking, and (of course) doing a little photography.

Kim spent much of her afternoon thumbing through seed catalogs and planning this year's garden.  The dogs played a lot of frisbee...
Kim spent much of her afternoon thumbing through seed catalogs and planning this year’s garden. The dogs played a lot of frisbee…

When diffuse clouds covered the midday sun for a little while, I grabbed my camera and set out to add some photos to a little project I’ve been working on – finding color in winter prairies.  The subjects that caught my eye on Saturday were prairie plant rosettes.  Most biennial plants (and some short-lived perennials) in our prairies spend their first year as a tightly arranged cluster of leaves close to the ground – a rosette.  Those leaves photosynthesize enough to get the plant’s root system started, giving it a head start on its second year growth.  Often, rosettes are found in areas of prairie that are recently grazed or mowed because competing plants are both short and weak, opening up space for new plants to establish.  Rosettes often stay green much of the winter, but the leaves can also turn other colors like red or yellow.

The green fuzzy leaves of black-eyed Susan.
The green fuzzy leaves of black-eyed Susan (Rudbeckia hirta).
Another rosette.  Maybe common mullein (Verbascum thapsus)?  I don't remember seeing mullein before at our prairie, but that was the best guess of my friend Grace Kostel when I sent her this odd-colored cropped photo...
Another rosette. Maybe common mullein (Verbascum thapsus)? I don’t remember seeing mullein before at our prairie, but that was the best guess of my friend Grace Kostel when I sent her this odd-colored cropped photo…

As I write this, I realize that I don’t actually know for sure how rosette leaves work.  I’ve always assumed that the leaves on a rosette lose their green color for a while during the coldest parts of winter and then green up again in the spring.  That is different from what most prairie forbs (wildflowers) do, of course, because their leaves drop off in the fall and they grow new ones in the spring.  Does anyone know if leaves in a rosette really can turn red/yellow and then green again?

9 thoughts on “Photo of the Week – February 25, 2016

  1. Rex Peterson February 25, 2016 / 9:28 pm

    Chris, the good news is the lower rosette is not common mullen. How do I send you a picture of one?

  2. James McGee February 25, 2016 / 10:15 pm

    Yes, the leaves can turn colors and then green up again. You should see Diapensia lapponica do this in sub-arctic environments during winter. The Eriogonum caespitosum in my rock garden also turns red for the winter. I recall being told the change in leaf color is an adaption for preventing damage from UV light, but I think it has more to do with the leaves needing to absorb the energy of the sun for warmth.

    • Pat February 26, 2016 / 6:48 am

      Some succulents will turn red when they get a lot of sun. Maybe there’s more than one reason for the change in color. Like leaves in the fall.

    • Kim February 26, 2016 / 9:05 am

      and it’s about different pigments within the leaves absorbing different wavelengths of light.

    • James McGee February 26, 2016 / 2:41 pm

      Of course the leaves of some individuals of certain species never turn green. Plant breeders have capitalized on this when selecting Heucheras. This is the reason there are Heucheras with names like Palace Purple and Plum Pudding among diverse others.

  3. steve clubine February 26, 2016 / 9:01 am

    The rosette kind of resembles hawkweed but looks a bit too dense. Not sure hawkweed is as far west as you are either. There aren’t many keys to rosettes.
    Imagine, something we scientists don’t know-the ecological function of color change in perennial plants.

  4. James C. Trager February 26, 2016 / 11:44 am

    I am leaning toward a Hieracium hawkweed ID, too.

    My unstudied hypothesis about the change in color in winter leaves is that cholorophyll degrades and is not rapidly replace in the slow winter physiology of the leaves, while other pigments are more enduring – rather like a really slowed down version of the fall color change. And leaves can green up again with warmer weather, although it seems like most rosettes are greener in their new growth than in old leaves.

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