I am in my 5th year of growing cottonwood. I've definitively verified two things
- That it can reduce
- That dieback can be overcome and completely avoided if you do the right things
The first point (reduction) is just a matter of learning deciduous broadleaf techniques, ramification methods, bonsai potting (don't expect reduction until you get OUT of that pond basket or anderson flat), and defoliation.
The second point is all about erasing sucker/waterspout buds as they happen. During spring, erase buds that are at junctions and along the trunk near the base. That's it.
@Lebiuqse , if you decide to grow cottonwood, then please print the second point out on a sheet of paper in your workshop and return to that point a year or two from now if you are scratching your head about how to figure this species out. It's suitable for bonsai.
Also, if you want cottonwood from the wild, perhaps take cuttings in early June instead of digging a tree up. Cuttings root in mere days in the summer (they root fast in winter too if you have a heat bed).
You don't need to and maybe shouldn't dig cottonwood up out of the ground, especially if it is protected in your area. But even relatively small cuttings develop fast. If you're wanting to be especially respectful of the species, then go look around during the winter after a wind storm and look for cuttings that have snapped off of cottonwoods and are now lying on the ground -- I have rooted winter-windstorm-snapped cottonwood cuttings collected off the ground which were as large as 47 inches long -- this species roots
VERY VERY EASILY even for
GIGANTIC cuttings and cuttings develop outrageously fast. Remember that when on you're on a hike.
Final tip, get used to hearing that it's a bad species for bonsai and remember point #2 above.