Leaf Color

The arrival of fall, at least in terms of leaf color, seems different this year.  Besides the timing being late, the colors, at least in my part of Wisconsin, are not as vibrant. Many trees are still green, and some are turning much later than normal. This post will be about this fall's leaf color.  

Timm's Hill, past peak, October 5, 2021

The timing of the change in leaf color is seemingly dependent on different climatic conditions. Rain and temperature being two of the variables. Sometimes rain and strong winds will take down the leaves before one has a chance to enjoy them. Seeing fall color can be a hit and miss proposition. An arborist on the radio on Oct 20, noted that if temperatures fall to about 25 degrees (F), the leaves on many trees will simply turn brown and then fall off.  He noted that tree leaves cannot take temperatures much below 26 degrees.  However, he also noted that the best measures for turning leaves are cooler nights, and sunny days. We have yet to have a frost this year for much of the state, and that is unusual. Frost will likely come this week with low temperatures expected in the low 30's Thursday and Friday. Depending upon the forecast the low Friday night (Saturday morning, really) could be as low as 30. This could start some leaves to change more than they have, but rain is anticipated for a good part of next week, which may well take down the leaves and affect the chance for color viewing.

Volunteer Hickory, in back yard
10/20/2021

When Land Girl and I were up north a couple weeks ago, it seemed amazing how quick the colors can change. My sister-in-law, about a week before our October trip to the north woods, noted that the colors had not really changed to a large degree, but by the weekend before our trip she said they probably were at their peak, at least in the Conover area.  At the time of our visit, they had yet to have a frost, my sister-in-law's impatiens were still going strong. On one hand the lack of frost seems to dissuade the theory of the arborist, but perhaps it was sufficiently cool, and a frost is not required.

Autumn Purple Ash, 10/20/2013

In 2013 I took photos of the autumn purple ash tree in my front yard, starting on 9/25 and recorded a photo every day until the leaves were all off. The last leaf of that photo series fell on All Saints Day, 11/1. This year, the colors of the tree lack the vibrancy I have seen in the past.  Generally one sees a great deal of purple, followed by yellow on the bottom.  This year the top is purple, the middle generally green and the bottom yellow. Yet, the purple is not as prevalent as in years past. It lacks the WOW! factor one normally expects from this UW generated cultivar of the white ash. Last year at this time much of the tree was bare, but some leaves clinging with some leaves not wishing to meet their fate at ground level to be raked and used as mulch on a flower bed. On 10/20/21, as I write this, the tree has fewer branches due to being pruned last year, many leaves are still clinging and the colors are varied, and not as vibrant. To the left of the ash tree you can see part of a birch clump which was yellow in 2013 on 10/20, but has mainly green color on the same date this year.   

Autumn Purple Ash, 10/20/2021

We have three locust trees in our yard, one a street tree and two in the backyard. Two of these trees, the street tree and one in the back yard, have pretty much lost all their leaves, with the street tree going first. The other one in the backyard is still predominantly green. They may well be different cultivars of the same species, but I am surprised at the leaf loss variability. The difference in color and timing has been noticeable in the past, but seems more pronounced this season. The hickory trees I have are just starting to turn, but I cannot say how this relates to past years.  I have noticed a maple tree in my backyard is mainly green to this date, but has lost some leaves which turned brown, rather than its customary yellow. Last year I recall it being a vibrant yellow glowing in the afternoon sun,before leaf drop. It has a few leaves with a tinge of yellow, but not many. Like the autumn purple ash, it lacks its vibrancy of years past. I suppose it is possible that tree color in my mind is related to years in which the colors are vibrant, and I do not recall the down years.  Although I have photo evidence of the autumn purple ash, but the detailed documentation is for one fall season--2013. I have other photos, but none as detailed with date of photo as the file name.

Two Locust Trees in back yard, you can see
part of the Autumn Purple Ash in the front yard

The fleeting nature of fall seems to portend the futility of holding onto color, and warmer temperatures. All the more important for us to enjoy the beauty of nature as autumn descends.  The shorter days have us realize that the arrival of winter is not far off, and our time to enjoy the fall can be fleeting. It will be interesting to see if we get a cold snap what occurs to the leaves (is the arborist correct?), and I suppose it is possible, that like in 2019, we may get a snow before the leaves are off the tree and picked up. The 2019 snow occurred in late October, and put a damper on leaf pick up. Given how late the colors are on many trees, they may hang on until November, or December.  Although Hickory and Oaks are known for having their leaves hang on a long, long time.