Please remember that the comments and placement are based solely on my sometimes questionable subjective judgement. Where I can, I try to give what I would intend to be constructive comment but please take it as only that.
As usual, a great range of entries both in terms of technical quality and of imagination.
And now for the results...
MichaelTMartinez: beautiful photo and clearly on-topic with lots of great detail in the main flower (whatever it is). Great autumnal tones of golds and yellows with the wheat stalks giving that harvest feel. The stem on the lower right is perhaps a little at odds with the rest of the composition.
Hughmac: another very autumnal photo with nice colours and tones. Great use of shallow DoF but your comment on the presence of loads of apples on the tree behind perhaps makes me want a little more background definition. The focal-point branch also a little soft in places due to shallow DoF but you nicely capture the single red leaf.
CmdrLaForge: lovely colours in the ivy - certainly one of my favourite autumn colour species, albeit very short-lived. The photo you posted is a little small to do it justice but I like the way the seals appear to be admiring the colours on display!
MacRy: great range of autumnal colours here from the greens through the golds, reds and purples. Nice use of shallow DoF to help isolate the main subject leaves and to differentiate the details on those leaves from the rest of the composition. Highlighting works well. To be hyper-critical, I think having the focus leaves more towards the centre of the shot would look more balanced but this may not have been possible in practical terms.
Someoldguy: classic autumnal shot with the added bonus of lovely reflections (despite the presence of ducks on the water). Peaceful. Like the way you've used the foreground trees left and right to form a natural framing for the colourful trees and lake. The log/branch and the bush in the centre foreground are perhaps a little intrusive but this is nature...
Cyclocommuter: like someoldguy, a more macro-view of autumnal colours. Trees are great and show a wide range of colours, particularly in the mid- to back-ground. Very unusual point of view - were you on top of a telegraph pole for this or use a drone? Despite the beauty of the foliage, my eyes are continually drawn to the road and what is happening there as the vehicles go through the narrow section, almost oblivious to the beauty around them
rx7dude: great colour and details of decay on the leaves. In many ways I like the very high contrast or high-key effect you've achieved but it perhaps goes a little too-far for my preference. I'd have preferred if you cropped more closely to the main leaves which would also have the added bonus of removing the (sensor dust?) spots from the blue sky. Good different take.
AlexH: more like the yellow/golds that we get in these parts. Lovely composition and you've handled the very high dynamic range in the scene very well: even the bit of blown-out sky is nicely positioned in the frame. Great how the low viewpoint of the road leads the eye into the trees with the road vanishing around the bend.
Indydenny: a nice evening photo with the unusual drone viewpoint. I like the long shadows and the relief they provide to the golf course landscape. A little short on the fall-colour front despite the obvious turning tree.
AlexanderofOz: at least we have some benefits over the Aussies! Despite the lack of the autumn colours, a lovely photo that captures the end stages of closing down for the winter and how it all ends on the forest floor. The almost monochromatic effect works very well here. I like how you used DoF to allow us to focus on one leaf in the plane of focus, letting us see the detail in that leaf. To be hyper-critical, the front/left out-of-focus leaves are a bit distracting: it would have been nicer to have them looking more like those on the right/back but that might have required a tilt-shift arrangement.
BigSky20: a lovely urban sunset/cityscape. The sky colours and clouds are great but ,for me, it doesn't really give that fall/autumnal feel - the trees (in Central Park?) still look pretty green. A difficult photo to take and you've done a nice job here. Might be worth cropping a bit to remove the window reflection bottom right and to emphasise the skyscape.
Apple fanboy: last-years pictures are fine by me! I really like this one - good composition and colours with a nice DoF. I like the way the composition gives the impression of the fungi fighting each other for space - encroaching on the rest of the frame. Fungi and autumn go hand-in-hand.
Deep Diver: I like your idea of representing fall by the leaves in the river and on the rocks but I think it would have worked more effectively by focussing on one part of the image. I'd suggest taking a portrait-format crop of the right side third of the shot with the cascade and the couple of nicely-defined leaves on the wet rock - the clump of leaves on the left is just a little messy for the effect to work.
3rd Place - MichaelTMartinez
2nd place - someoldguy
1st Place - AlexH
Particular praise to Apple fanboy and to MacRy. I had particular difficulty with MacRy's entry - placed then unplaced several times. It may sound trivial but the position of the focal leaves in the frame just pushed it out for me.