Seasonal weather variations (temperature, rainfall, etc), and plant variety

Interesting question. We are in east central Iowa and we have been so excited with the fall colors this year. T he maples are beautiful with their many different colors. The Korean Spice Viburnum is dark red, the amsonia hubrechti has colored for only the second time in m any years, the burning bush is spectacular. On the other hand, my fothergilla has never colored. I'm sure it has something to do with the weather, but we feared there would be little color due to the drouth and extreme heat. We still haven't had a killing frost, but that is coming in the next few days. The leaves have stayed on much longer than usual. Even the sunburst locust is putting on a colorful show. It's leaves are usually long gone by now Whatever the reason, we are enjoying the show.

Several factors affect the pigment production in foliage. Dry weather and late summer sun causes the anthocyanins to increase...which is why our damp and grey summers rarely lend themselves to vivid autumn colouration. Of course, we can search out those plants which are more likely to glow...such as some of the rowans, the maples and liquidambers. Here in the UK, a soft butter yellow is our most dominant autumn shade.

Shorter day length and longer cooler nights are the main factors. A warm, wet spring then good summer weather followed by sunny fall days with cool nights brings great fall colour.

We have had 3 terribly hot dry summers and the fall colour was generally far from spectacular all three years. I miss the wonderful display we usually get.

In my area (NJ/Zone 7a/b), the continuation of warm weather in the autumn has resulted in dull colors for several seasons. Leaves will stay green, well into the autumn, until there is a hard frost, then, they just drop or linger on the trees frost-killed. Lots of different factors involved though.

a lot of trees in my area were severely injured in the two ice and snow storms.. and im wondering if that might be part of why yellow is predominant this year.. with many oaks going straight to brown ..

stress is stress... and its not about stress this fall.. you have all insults to normal from spring emergence thru today...

im just not sure wood damage in winter to hard wood would also be a stress ..

ken

"..with many oaks going straight to brown .. "

I've noticed this, too.

Oaks in general do not have brilliant coloration, not compared to maples, but maples in my area have been in decline. I have lost two maples in my yard over the last several years, a Red Maple and Sugar Maple. Japanese Maple is the surviver but does not color the way it used to color (from purple to scarlet red in November). Need to check out what the Gingko and Dawn Red did this year (no idea if they are still green, yellow or fallen, or bronze in the case of the Redwood).

On the contrary, oaks here in upstate NY seem to be coloring much more brightly this fall than I can remember in many years: lots of flashy reds/oranges on trees that normally just "brown up" and then hang for most of the winter.

Fall color here generally outstanding, tho some tree species can be an exception. Many of the numerous low elevation sugar maples near me simply lost their leaves early on. Some tuliptrees and coffeetrees experienced the same thing. I suspect heat and dryness bothered those trees. Some trees colored excellently like my katsuratree and ginkgo because the killing freezes held off.

It's weird in my area because we've had the wettest fall so far(average 2 in per week since late August) but fall color is spectacular than any other year imo. Very early too.