Chinese Elm Seedlings

Hello everyone! I have a question about Chinese Elm from cuttings. I took several cuttings from my Chinese Elm early this past fall and took them inside and put them in a terrarium where theyve rooted nicely and are growing rapidly. By spring they will be nice seedlings to put out in the growing bed, that is if i can keep them alive that long. They are growing fine but now that thier going on about two feet tall they fall over. I had to stake and tie them up to keep them straight and from laying down. There growing great but thier not thickening up enough to keep themselves up right. Does anyone have any ideas why? I thought maybe it was bcuz theres very little wind just what a fan puts out and that maybe thier not thickening bcuz theres no wind and weather to strengthen them. I dont know? Any suggestioons or ideas? Thanks

hi

poor light - a tree not recieving intense enough light will stretch up looking for more.

cut them back down to a few inches though, then they will produce more branches, stop falling over and get a bit chunkier before going outside.

cheers

Marcus