Carotenoids, Anthocyanins Ready For Their Big Show

Q. Why do leaves change color in the fall?

A.  Deciduous trees are responsible for our annual autumn color display. In particular, oaks, maples, beeches, dogwoods, and hickories are among the trees best known for painting our southeastern landscape with brilliant hues before entering into a winter slumber. If you’re on the hunt for fall color look no further than the deciduous broadleaved trees growing in our surrounding yards and forests.

All the factors affecting color change are still not fully understood, however scientists have discovered some of the basic causes for autumn color. The three main factors that cause autumn color to happen include the increase length of night or darkness, cooler nighttime temperatures, and the amount of moisture in the soil. In response to shortening day lengths the primary pigment chlorophyll, which gives leaves their basic green color, starts to slow down production. As light and temperatures continue to decrease, chlorophyll production stops and eventually all the green color in a leaf is destroyed unmasking two other plant pigments. These pigments include carotenoids and anthocyanins. Carotenoids are responsible for producing yellow, orange, and brown colors, where as anthocyanins produce reds and purples. With chlorophyll gone, the carotenoids and anthocyanins present in the leaf are able to show off their colors. These pigments come in different combinations that are characteristic of particular plant species, which is why oaks turn red in the fall and hickories turn yellow.

Autumn color displays not only provide beauty to a landscape, they also help aid in plant survival. It is crucial that broadleaf plants lose their leaves in order to prepare for a winter where temperatures fall below freezing. Evergreen trees such as pines and cedars are able to keep their needles through the winter since they are covered with a heavy wax that prevents the fluid inside the needle from freezing. In contrast, deciduous broadleaf leaves are thin and lack this protective wax and therefore leaf fall must precede each winter to prevent the plant from freezing.

As leaves turn from green to brilliant shades of crimson and gold, compost enthusiast everywhere cannot wait for those leaves to become a carbon source in their compost bin. In natural areas, fallen leaves decompose where they land restocking the soil with nutrients and becoming food for numerous soil organisms vital to the forest ecosystem. Unlike natural areas, many people have turf in their yard where it is necessary to remove fallen leaves in order to allow light to reach their grass. Compost is the perfect solution to getting the most from your raked leaves. It helps gardeners recycle valuable nutrients back to the garden at virtually no cost and it keeps yard trimmings out of our landfills.  

If you’re more interested in color than compost you may want to consider planting your very own fall color garden using deciduous broadleaf trees. The United States National Arboretum has a list of plants that display vibrant fall colors. Visit ww.usna.usda.gov/PhotoGallery/FallFoliage/FallColorList.html to obtain this list. Another way to enjoy autumn’s color show would be to take a drive along the Blue Ridge Parkway, which is one of the most popular scenic byways for observing nature’s fall beauty. Before driving to Western North Carolina, call the Forest Service’s Fall Color Hotline (1-800-354-4595) to find out details about the status of the color change along the Parkway.

Upcoming gardening events in Wayne County:
• The Wayne County Master Gardener Holiday Workshop, Making Green Decorations from Natural Materials, has been CANCELED. It will not be held on November 14th from 9 a.m. till 1 p.m. For more information on this cancellation please contact Diane Lynch at 919-731-1525.

NCSU & NC A&T University commit themselves to positive action to secure equal opportunity regardless of color, creed, national origin, religion, sex, age or disability.  In addition, the two Universities welcome all persons without regard to sexual orientation.

Karen E. Blaedow
Extension Agent
Horticulture
North Carolina Cooperative Extension
Wayne County Center
P. O. Box 68
Goldsboro, NC  27533
E-Mail: Karen_Bussey@ncsu.edu
Phone: 919-731-1525
Fax: 919-731-1511
http://www.ces.ncsu.edu/wayne