Fall Colors and Leaf Drop  

TOPIC: Fall colors and leaf drop

== 1 of 3 ==
Date: Sun, Oct 26 2008 8:21 pm
From: Steve G


Here in N Ohio, on October 26th, most oaks are still green, and many
other trees are just beginning to show fall colors and leaf drop.

Rocky River, Ohio Fall 2008. Photos by Steve Galehouse

Twenty years ago, tupelos would begin to color up in August; now it's
in mid October. It seems "fall" has been pushed back at least a month
from what it used to be. Any comments or observations?


== 2 of 3 ==
Date: Sun, Oct 26 2008 9:44 pm
From: "Edward Frank"

Near Reynoldsville, PA


I haven't seen the same thing here in PA. I don't think the dates of color are being pushed back in this region. I have been trying to find a listing of dates of fall coloration on the internet for periods in the past for comparison purposes, but have not had much luck. In general the process really seems according to the literature to be triggered by changes in day-length and not by temperature changes. Therefore since the length of days have not changed as a result of global warming, the dates of color change should not have changed. I believe there is a difference in the dates of color change and leaf drop from planted trees of a more northern origin is earlier than those of local origin. I don't know what to say about your experiences with the later coloration in your area.


== 3 of 3 ==
Date: Mon, Oct 27 2008 12:57 am
From: James Parton


Douglas Falls, NC - photo by James Parton

Here in WNC we are just past peak color. I visited Lowndesville SC
yesterday and the leaves there are just really beginning to turn. They
are a little south of us and about 1300 feet lower in elevation.


October 28, 2008


Because both temperature and day length control formation of fall colors. Up here temperature used to be the primary controlling factor (it got cold enough to cause leaves to change color and drop before the days were short enough to do so), but now it doesn't get as cold as early, so day length has more chance to cause the leaves to change.


October 28, 2008

Lee and ENTS,
I guess my thoughts were ill-formed when I first posed the question.  What I am thinking is that there are two mechanisms that cause the leaves to change colors and fall.  One is they are nipped by frost and drop.  The other is that they drop because the process is triggered by the change in day length.  One sort of backs up the other.  If the cold doesn't get them, then the leaf change goes to its fail-safe option of change in day length.  Why would the trees not simply wait until cold caused the leaves to die off?  Why have this day-length mechanism at all?
There must be some disadvantage to allowing the leaves change and drop to be triggered by temperature change, or some advantage to the leaves being triggered by day length changes.  What is it?  On the face of it, it would seem it would be best overall for the trees to hang on as long as possible, to extend the growing season, but the day-length trigger must have some advantage that outweighs the gain from extending the growing season at the cost of the leaves freezing.   This must be some specific ratio or formula balancing the benefits and costs of both options. Why is the change at a specific day-length? How specifically is this leaf change formula from day length change determined?   It may be different for different species.  Like now the black gum has long since fallen (thin leaves), the maples are mostly down, but the oaks and tuliptree leaves are still hanging on and to a large degree green.  Why is there this pattern, and why is color triggered by these day length changes?
It is a genetic mechanism.  Clonal colonies all seem to change color at the same time.  Trees transplanted from the north change colors sooner than southern trees.  Is the time of nut production or fruit production triggered by the period since leaf-out or also by a change in day length?  That would apply to blossoming in the spring - is it a certain time after leaf out or set by temperature or set by day length?  I know blossoming can be delayed by weather, but what if the weather is good?  I am just trying to understand the processes happening.

October 28, 2008

Closeup of the trees from the cliff at Rattlesnake Knob.  October 13, 2008- photos by Elisa Campbell


as New York state gets its first snow storm of the season - possibly 6-12 inches in the Catskills are predicated - it seems to me that trees with leaves on them are severely impacted by heavy wet snow - breaks many branches. So there would be a real advantage to losing the leaves before snow is likely, I think.
Elisa Campbell

October 28, 2008

Ah, my favorite topic: leaf color change, abscission and dormancy -
favorite because it is so beautiful and dramatic and our knowledge is so

A couple of observations:

1 - dropping leaves is an active process and takes time; that is, trees
form an abscission zone of dead corky cells at the base of the petiole,
sealing off the xylem and phloem, then the leaves are able to fall,
sometimes in unison!  I have come upon a ginkgo that has gone golden
yellow, and then one morning, all leaves begin floating to the ground,
in the absence of any wind, gently carpeting the space around the tree,
leaving a stately naked skeleton with a golden skirt - as good as any
Goldsworthy scuplture!

2 - trees that are frost nipped before they complete dormancy hang on to
their leaves, until the petiole is frayed by the wind, or is pushed off
in the spring by new leaves emerging - oaks often do this up here in MA,
possibly because the day-length sensor is out of phase since they are on
the northern edge of their distribution

3 - leaves that fall on their own, e.g. through dormancy and abscission,
have very different nutrient contents than those that stay - so
resorption of nutrients may be one selective pressure for getting the
job done before heavy frost shuts the whole process down.....the counter
pressure is off course getting that last little bit of carbon fixed into
starch - so trees gamble!

4 - color change is even more wonderful and mysterious - hypotheses
abound!  but the reds (anthocyanins) definitely develop during the
dormancy process and are not there before - at least in a colored form -
they may take on color by being combined with sugars; and the pattern of
color change is so different one species to another - sugar maples show
a gradation in color that correlates with light intensity and/or
duration - I tell the students that trees are the first photographers;
frequently you can pull away one very red/golden leaf to reveal an
outline of the that leaf in green on a leaf below it

5 - black gum leaves turn one at a time; green next to red, apparently
NOT influenced by light - poplars keep a tuft of green leaves at the
very top of the tree until the very end

6 - and, sadly, flagging, or branches turning all red or yellow before
the entire tree goes, can be a sign of disease or distress in that
section of the tree.

What fun.

Larry Winship

Thank you.  An excellent response that addressed my immediate questions.

October 28, 2008


I guess that seeing the leaves of understory buckeye trees turn yellow and drop during mid August is the one of the first obvious indications that fall is on the way and it is one of the few color changes of the year that will make my wife groan....she hates winter!
Russ Richardson


October 28, 2008


Perhaps the timing of leaf coloring and drop can be thought of as dependent on two main factors: 1). Day length, and 2). Environmental stress.

Color due to reduced day length is obvious, but color due to stress might be caused by: cold temperatures; increased daily temperature fluctuation; drought; physical injury to tree; or insect/disease infestations, and other factors I'm sure. I think we have all seen the occasional tree in full fall color, but displaying the colors in July or August, not October. This could not  be caused by cold temperatures, but rather indicates the tree is in some sort of stress, and also shows that reduced day length alone is not the only cause of fall color. I think in the area where I live the weather patterns 20 to 30 years ago  were such that the forest in general was in a more stressed state in early autumn, and that combined with day length created "earlier" falls, by about two weeks.

As a separate comment, concerning intensity of fall colors independent of timing, it seems like young trees typically display brighter colors that mature trees, especially among oaks. Pin oak is the commonest oak in my area, and mature trees, 2' or more in diameter, usually turn from green to buff or just right to brown, while saplings in the woods are often brilliant crimson red. The white oaks and red oaks show the same pattern, with young, vigorously growing trees producing the best fall colors.

Steve Galehouse

TOPIC: Fall colors and leaf drop

== 1 of 1 ==
Date: Tues, Oct 28 2008 8:14 pm
From: Randy Brown

Is it just my imagination or do old trees of a given species tend to
turn before the young ones?

== 2 of 9 ==
Date: Wed, Oct 29 2008 5:50 am
From: doug bidlack

That's just the opposite of what I observed this past weekend here in southeastern MA. The scarlet oaks are starting to turn right now, but it varies with size/age of the plant. Those that are no taller than me are mostly brilliant red and those under 20' or so are maybe halfway there. I've got this mental note that says scarlet oaks tend to peak around the first weekend in November and I think that will be fairly close for this year. As Steve noted, the larger, older oaks don't seem to be very brilliantly colored. Every year I search for a brilliantly colored very large scarlet oak and every year I fail to find one even though these are among the most common upland trees around here. This pattern doesn't seem to hold as well for maples though. Even very large red and sugar maples are absolutely beautiful in the fall. I do recall a sugar maple that I planted with my parents in southeastern Michigan that did turn a brilliant orange when it was
younger, but then settled into a lovely, but much less spectacular yellow later in life. This tree later died and I wonder if it just wasn't happy due to drought stress in the late 80's.


== 3 of 9 ==
Date: Wed, Oct 29 2008 8:43 am
From: "Edward Frank"


There has been a dramatic change in the weather here since yesterday. Two days ago I was raking leaves in my yard. The black gum and red maples are for the most part leafless. The tuliptree and red and white oaks around the yard still are holding most of their leaves. Yesterday was windy. Gusts were recorded nearby at 40 mph, with a strong wind blowing almost continuously as the front passed. A few good sized limbs blew down into the yard. Today I was awakened by the sounds of tractor trailer trucks stuck on the hill in front of my house. This is route 322 which parallels Interstate 80 across much of Pennsylvania. Generally the big rigs travel I-80 unless there is a problem on the interstate. The truck in the photo took abut 1/2 and hour to inch up past the width of my yard. about twenty minutes later it was backing down the hill.

The recent discussions on leaf color have been interesting and I have learned a lot about the process. This had been one of the most colorful fall foliage seasons in recent memory. I guess the absence of cold-induced leaf mortality allowed the trees to turn colors fully at the time controlled by day length. As Larry Winship says. The leaves are gambling with their shut down mechanism. The tuliptree and the oaks may have waited too long by the looks of the snow outside, but the maples timed it about perfectly. I have enjoyed the animated discussion of leaf color changes. The response to my request for fall foliage photos has been excellent. I was forced to downsize the photos posted on the fall 2008 foliage webpage http://www.nativetreesociety.org/fall_foliage_2008.htm simply because the number of images I received and posted to the gallery. Some are simply fantastic.

Ed Frank

"Two roads diverged in a yellow wood, And sorry I could not travel both. "
Robert Frost (1874-1963). Mountain Interval. 1920.

== 6 of 9 ==
Date: Wed, Oct 29 2008 3:12 pm
From: "Steve Galehouse"


As another point of interest regarding fall color and leaf drop, I think it
is interesting that many, if not most trees of European origin retain
foliage longer and color less vibrantly than native species. Norway, hedge,
and sycamore maples are all still green in my area, as are English oaks and
European beeches and hornbeams. The provenance of most of theses species is
well north of the latitude of the U.S/Canadian border, so I'm not sure how
that relates to the observation that (native) trees from more northern
location lose leaves earlier than trees of the same species from more
southern seed sources.These European trees seldom exhibit red or orange fall
color, typically turning yellow or brown instead. It seems like nearly all
trees or shrubs that display red or orange color are from eastern North
America or eastern Asia.


== 7 of 9 ==
Date: Wed, Oct 29 2008 5:52 pm
From: "Edward Frank"


That one I can address. It isn't strictly latitude, but the climate of the region the tree come from. From farther north, I was meaning farther north in North America. We are on the east side of a large land mass and have a climate that is both much colder in the winter and hotter in the summer than those in England and across much of Europe. These areas are moderated by the expanse of the Atlantic Ocean and the north sea. So trees from these area stay in leaf longer, because they come from areas that do not get as frigid as early in the year as it does here in the eastern US. The fall colors here are supposed to be the best in the world, when we have a good late frost, as we have had this year. Different species produce different patterns of colors. I guess someplace has to be the most colorful. Red and sugar maples are among the brightest colored of the landscape dominating species.


"Two roads diverged in a yellow wood, And sorry I could not travel both. "
Robert Frost (18741963). Mountain Interval. 1920.

== 9 of 9 ==
Date: Wed, Oct 29 2008 7:24 pm
From: "Steve Galehouse"


I know what you are saying--North America is "redder in tooth and claw"
compared with Europe, as far as climate is concerned, and the autumn display
of tree colors is much more vibrant here. My ten favorite species for fall

Sugar/Black maple
Red Maple
White ash
Bitternut hickory
Scarlet oak
Staghorn sumac


TOPIC: Fall colors and leaf drop

== 1 of 2 ==
Date: Thurs, Oct 30 2008 8:32 am
From: "Edward Frank"


In this area of PA the woods have been cut over again and again. Most of the trees are in the 80 year range in age. They are dominated by red maple, various oaks, and birches - mostly yellow birch. Other species are present, but in lower numbers.

I guess my favorite must be red maple, because they have nice color and basically that is how fall is supposed to look in my mind. There are scattered black gum that give a burst of brilliant red. With the sun shining on them or through they look fluorescent red in brilliance. The birches provide a yellow back drop. I enjoy, unlike many people the various subtle shades of tan and brown often shown by the oaks as part of their fall display. Their reds and yellows aren't that inspiring, but myriad tones of brown displayed has some quality that appeals to me. The other tree species form little points of contrast within this larger context. As I said before this has been a memorable season for color in this area of Pennsylvania.

Ed Frank

== 2 of 2 ==
Date: Thurs, Oct 30 2008 1:35 pm
From: Andrew Joslin

This year's foliage display is so good that even the oaks are looking
brighter than I can remember seeing. The colors are far from drab.
Scarlet and Pin Oaks are looking great and Red Oaks are showing a variety
of color from a luminous warm yellow to some interesting burnished shades
of red. Hickories (Pignut I think) are peaking bright yellow, a great year
all around.

Andrew Joslin
Jamaica Plain, MA