As soon as deer season is over I plan to bring out the hatchet and chainsaw before the ticks/snakes get bad, etc. I have always heard it is best to hit trees (such as sweetgum) with herbicides in the fall so that it will better transported to the roots resulting in a good kill. With spring on the horizon, I would guess the general movement is from the roots up to the limbs and leaves. My question is, should I expect it to be harder to get a good kill and/or should I do anything different? I plan to do hack and squirt in some locations and a complete cut at the tree base in other spots of the property. I typically spray either concentrated gly or gly mixed with a little imazapyr after cutting.

How big of trees?

If the trees aren't too big I'd cut then immediately treat the cut stump with Gly diluted 50:50

All sorts of sizes.

I would start now! anything later than late February may just be in vain.

I don’t live at the farm. Gotta do it when I can.

Then you should move! 😉

The bigger ones I cut around here I drill some holes in stump and put some used motor oil in the holes. Little ones I spray with brush killer when the tree have leaves on them.

Or id suggest tordon.
This to the smaller ones, the bigger ones you can girdle. Cut one or two rings around the tree deep enough to sever the cambien layer.
Depending on what you want it for hinge cutting those smaller ones will add cover and more tonnage at deer level.