For all of them, spring, after the ground thaws enough to dig, right up until the buds start to open.
Perfect! Thank you for that info. I'll probably shoot for end of march/first week in april then... right after ski season!
There's a second collecting season, late summer, until the middle of autumn. Success is not as high, but is not too bad.
So, this period would from mid september through late october roughly? Basically, right as foliage is dropping from the tree?
All the trees you imaged are small in my book, I would look for taller trees with trunk diameters over 3 inches to about 5 inches. Yes, you will often be looking at 12 foot tall trees. You just chop 'em down to 3 to 6 inches tall the day you collect them.
The Sugar maple in the yard is about 2.5" maybe 3". I understand the appeal of collecting the larger ones for more immediate trunk width but I want to start fairly small for now and just learn the basics of keeping them alive... working with a few different trees. I have another couple trees in my backyard that have that size trunk which I may try and do the chop on in a couple years.
Thanks for the advice Leo.
Rather than "not worth the time" let's use the friendlier term "more advanced material - for one reason or other".... For example, I would consider wisteria extremely difficult material due to: large compound leaves that don't reduce, viney growth, difficulty balancing foliage constaint with flower production. However, if you happen to have one that looks just right, that blooms just when you want, it is high on the list of the most beautiful bonsai out there

But for me - not worth the time

"
Understood. I can see the clarification being useful. No species should be off limits, just differing amounts of difficulty.
One of the trees on your list, Sugar Maple, is a personal favorite of mine. Hard to get the leaves to reduce, but as long as you plan for larger scale bonsai, the leaves become less of an issue. I wish you good luck growing a nice tree, because if I could grow them here in southern California, I'd have 100 of them
We have tons of them here in NJ. I had actually grabbed a bunch of seeds from a tree in the park to plan on growing this coming spring but they got moldy in my basement... I didn't think that out well at all. It's cool to know that the species is a favorite of someone with as much experience as yourself. Gives me more incentive to work on it. It has a nice curve at the base of the trunk which isn't visible in the picture.
My Tree's and I listen to Metal Core
I really like the one with the wicked looking nebari middle row to the left in the brown pot. The one in the white pot bottom row also caught my eye. Very nice trees!
I'm not huge into metalcore... the closest I've gotten to Metalcore are some of the Gothenburg bands from the late 90's early 00's like Dark Tranquility, Soilwork, early In Flames, At The Gates... but some of those aren't even really what most would consider metalcore.
My genres of interest mostly are US Power Metal like Fates Warning, Queensryche, Liege Lord, Manilla Road, Omen, and that ilk. Also really into Old School Death and Black Metal like Bathory, Venom, Slaughter, Death.... I would consider myself, if not a scholar, a connoisseur of New Jersey metal... Whiplash, Attacker, Morbid Sin, Ripping Corpse, The Beast, Evoken, Abazagorath... that ilk. I cover a lot of stuff on my website:
https://contaminatedtones.blogspot.com/
I also do occasionally post nature photos and whatnot there, but it's mostly metal. I've been doing that blog since 2008. Have a fairly decent readership. I am fairly entrenched in the local music scene here since I have been attending shows for many years as well as playing shows continuously for the past 10 years or so. There is a
picture of the small Acer Negundo I grew this summer there though.
So I took the advice
@Shibui and
@Leo in N E Illinois posted in the seed thread. that I trim the root that one of my acorns had been growing... I didn't realize it had gotten so long! It was actually about 5" long. I cut it back to what appeared to be the first sign of a new root tip branching off the longer taproot. My thought is that at least clipping it there it would have another root tip to divert energy to and maybe grow a few more from the cutting spot. It has not yet pushed out cotyledon. I'm hoping it does ok with this clipping:

Before cutting

After cutting. The little white line is the root I saw growing off the side so I cut back to there.

The cut off segment. I had no idea it had grown so long.