lol...I know that seller! Not personally...but I know exactly what you have
And the type of growth you have there looks normal. I believe these are from the same seller:
View attachment 338272
I got these about 2 weeks ago for something to play with. I used to have some larger willow including a weeping willow that was starting to form up nicely but I went out of town to visit grandchildren and they didn't survive the heat
I was very much more careful with my other trees and moved them out of the heat and arranged for someone to check on them but the willows were in a corner and forgotten...mostly because they are so easy to come buy here!
But first things first! Go to the top right of the web page and look for your user name. Click on it and go to account details. There is a spot there for "location". Nearest recognizable metro are is probably good enough for most US people, but BNut is international. It'll help those outside the US is you also add your agricultural zone. The US zone is fine...the details are easy to look up as necessary. You do that and next to your icon on the left of your posts people will see where you're located. It helps a lot and you won't have to repeat yourself in every post
Second...that is a decent amount of growth...Nice work! You'll likely see a lot more once they become used to being in soil
Especially if you fertilize them a bit! If you have a NAPA autoparts nearby, ask for NAPA 8822: oil dry. It's really diatomaceous earth...it'll look like little bits of gravel. It's a cheap, long lasting, easy to maintain soil and I can tell you from experience that willow do well in it! That picture above is NAPA 8822 plus some chunk coconut coir. You don't really need the coir. I use it to help stabilize the tree while it roots out. The one downside to NAPA is it is very loose and the trunks may need some support until the trees root out a bit. Do try to stay away from big box store brand x soil. It can work...especially for willows...but there are disadvantages to it as well. I won't say more unless prompted, but soil discussions on sometimes devolve...everyone has a favorite...no one is wrong...but we all have different conditions to contend with...
Once in a soil, the roots will have some structure to grow into and really solidify those trunks in space. Then the branches won't feel/look so fragile. If you do go with the NAPA...or any inorganic soil...you will need to fertilize occasionally. That's one of the big reasons you want to get out of pure water. Unless you're fertilizing the water...the tree will eventually run out of nutrients and you'll have issues.
The corkscrew willows will tend to continue to grow straight up. You can trim them back anywhere and they will tend to branch from the base of the remaining leaves. Trim them far enough back and they may even form new branches directly from the trunk. That's part of the "art" of bonsai...learning exactly where to make those cuts to trigger what kind of growth you want for a particular species. For now...let them run as long as you can and trim them back only enough to fit your space. You want as much growth as you can get to fatten up those branches. It is not likely you will want to keep that stick for long. In a year or 3 you'll want to be thinking about where an interesting kink in a branch is and cut below there and root it off again. You can get several nice trees off one stick that way and each will be better than what you'll get from the stick itself.
The weeping and dragon willows will have a more horizontal habit but otherwise, same thing for now...let them grow as long as you can tolerate, but don't be afraid to trim back if you're out of space. The further you trim back the more likely new growth will push back to the trunk rather than from the leaf bases. If you leave a couple of leaves on a branch, they should favor growing from leaf nodes rather than forming new branched from the trunk but that's not guaranteed.
You might want to read up on colonizing plants and their growth habits. Willows are colonizing plants...hence the rapid growth! They want to move in and establish themselves quickly. There are downsides to that though. They tend to give up on branches...especially over winter...in favor of new branches. In a pot, they are a little more predictable, but read up on how they tend to grow and pay attention to how they react when you make certain cuts and you'll be a long ways towards making something interesting.
They are otherwise pretty bullet proof! Do realize, though, that even with fast growing willows, you are about 2 decades away from anything much like the pictures that seller shows of these guys as bonsai.
..
