Leaves is leaves is leaves. Some take longer to break down than others, but they break down eventually. The soil the tree grows in does have some effect on the leaf. Ones grown in lime rich soil tend to have lime in them.
Leaves from evergreens are more difficult to deal with, but even they break down in time.
Conifer needles are a different matter though. They tend to make soils acid.

For me, any leaves that blow onto my property is fair game. Usually it's every tree in the neighborhood; Lucky me. YIPPEE!!

I must own up to collecting leaves from 100 yds away at the end of the road where they’re plentiful. I wonder if people sometimes think I’m a roadsweeper ?

If you are going to collect leaves to make leafmould, then I believe that beech is one of the best as it breaks down easily and it looks like the ones that you have displayed.

That's the best kind of mulch. I put a thick layer over my vegetable bed and let it sit there all winter, then til it in the Spring.

Hey, thanks J, the right leaves at last - quite made my day.

And I’ve done exactly the same thing myself B.

Hate to contradict you jimmytheone, yes they are beech leaves but take 3-4 years to break down to a lovely leaf mould. I have a large beech tree in the garden and the bags get stored in strict rotation behind the garage. Our tree furnishes us with 15 bags every year. they get well mixed and chopped up with the lawn mower too. They are high in tannins like oak hence the time it takes to rot.
the ash and sycamore break down much faster 12 -18 months usually.

either way they will rot down providing there are aeration holes in the bag and they are slightly damp.

Good point, shredding up the leaves first will ready them much faster. Shred them, go over them with the mower or smush up the bags a few times, stomp on them.

Either way, your 'knowledgeable' friend was leading you astray. Those leaves will turn into useful stuff, sooner or later.

I agree with Seaburngirl - we get loads of sycamore, ash and beech leaves and the beech always take longer to break down.

Thankyou Hank for asking this question. Our red oak leaves take at least 3 years to break down but I do put them in whole. I love the odd beech leaf I get from a garden up the road and didn't know they take so long to break down. I thought they would be helping the oak along!
Stera I'm so grateful to read your post about sycamore because I read years ago that it's not good for leaf mould and I've mistakenly always put them in the council bin. This year I'll definitely use them for my supply.
Even when the leaves have not completely broken down, I still use them to improve the soil. Don't know if this is a bad idea but it doesn't seem to harm plants.

Well I don't know if Sycamore leaves are bad for the garden but that's what we have so that's what we use...
I don't know how you would tell if they were bad for the garden - does anybody here? What is bad is the hundreds of seedlings from the parts that haven't rotted down...

they are not bad for the garden. they rot relatively quickly.
oak and beech have relatively high levels of tannic acid in them. they will lower the pH of the soil slightly. In the wild they add their nutrients slowly to the woodland floor.
so no worries.