Spectacular fall colors one bright spot in 2020
It seems like it was only about two weeks ago that I was wondering when the trees would start putting on their spectacular display of fall colors. Well, as I seem to notice more and more often as I get older, time flies by much too quickly when you are having fun!
I was expecting a truly spectacular fall color season since mid-summer, and I have not been disappointed. This year’s spring and early summer drought conditions prevented many of the common leaf spot diseases that often lead to premature defoliation of maples, ash, birch, cherry and other deciduous trees. A lack of rain early in the season means little infection and most trees have entered the fall with a full canopy of leaves.
There is a pretty obvious time lag this year between the early fall color of maples and the later display by oaks. Most of our forested landscape is dominated by these two groups, with a much smaller percentage of hickory, ash, aspen, birch, ironwood, beech and black cherry. The maples are already orange, gold, yellow and sometimes fiery red, whereas the oaks are still primarily green, at least in my neighborhood, but, when they turn, the color will be mostly red.
The yellow and orange colors are pretty easy for a tree to display, because the pigments that create these colors are present all season long (xanthophyll). They are masked by the green chlorophyll pigment from early summer until now, when the tree literally puts a plug on the plumbing that connects the leaves to their water supply. To prepare for leaf drop, the xylem vessels (water pipes) from the roots to the leaves are plugged up by the tree, which cuts off the water supply to the chloroplasts. Without water, the chloroplasts die and the green disappears, allowing the yellows to show off.
With the red/purple pigments (anthocyanins) it is a totally different story. These pigments are manufactured by the tree in the springtime, when they act as a sunblock to protect the newly developed and fragile chloroplasts from getting burned up. Many plants will begin the season with red or pink leaves that turn green as the season progresses. I have observed that poison ivy, in particular, begins the season with distinctly red leaves for a couple of weeks as the leaves expand. What remains a scientific mystery is why the tree expends the energy to produce these complex red pigments again in the fall, after the green chloroplasts are long gone.
No one completely understands the role of the red pigments in general, except as spring sunblock, but I am very grateful that nature has chosen to do this extra bit of work, as fall comes on. It is like nature is saying, “Check this out right now and enjoy it, because you know what is coming soon!”
There are only a few places on the planet that gets this special treatment each year and nowhere is it more vibrant than right here in the great Northeast! The Rockies and parts of the West may have mass displays of mostly yellow colors, as for example in much of Colorado’s aspen forests. The evergreen-dominated forests of the Pacific Northwest (when not on fire) obviously don’t change color as dramatically as our hardwood species do.
Even our so-called “evergreens” shed their old needles each fall and sometimes it is quite dramatic when it happens rather suddenly. White pine trees will generally drop the previous season’s needles, or their 2-year-old needles, after they turn yellow, and sometimes this causes concern among observers. If all the needles on your pine tree turn yellow, that usually means it is dead, but if only the inner needles turn yellow and drop, that is normal.
We do have one deciduous conifer in the region that sheds all its needles in the fall after they turn a gorgeous yellow/orange color. That tree is the larch and its fall color is also rather spectacular, as it usually occurs a few weeks later than the maples, or the other hardwoods. I have one “native” larch tree on my property (Larix laricina, also called Tamarisk), that I transplanted almost 20 years ago from the Adirondacks, where they are pretty common, but I also have about four acres of intentionally planted European larch (Larix decidua) that were planted by the family who owned this property at least 50 years ago.
I have told many homeowners over the years that if the conifer tree growing on their lawn has all its needles turn yellow in the fall and then drop, it is either a larch or it is dead.