Weird tree generation

Hey guys I've made a tree I did few test to make it better and there is still some issues :

Here my tree is flying,

https://zupimages.net/up/20/27/sfun.png

https://zupimages.net/up/20/27/nf8o.png

Here my tree is in the floor,

https://zupimages.net/up/20/27/9u4r.png

and here my tree is in an other tree,

https://zupimages.net/up/20/27/zsnj.png