Question
Hello, I want to know if it would be possible to grow Aspen and Birch trees in Southern California. (High desert)
Thank you.

Answer
The climate in locations will dictate which tree species will do well in areas. That does not mean that a species will not grow there as a yard tree but when a tree is far out side its natural range it needs care usually water and the growth rate will not be the same as in it native habitat.

Saying that people have planted trees far from the natural range and the trees do well but the life span is deduced )say from a normal of 80-100 years to 20-30 Years).

Aspen-there are various species of "aspen" that are adapted to different ares. I would check with your local nursery and if they have the tree it will grow there OR if you are not far from the native range try it and see. Here is a web link to the aspen range in Calif.  http://mojavedesert.net/habitat/asp.html

Birch--there are at least 20 species of birch in the US, They are well adapted to all climates. I am sure one will do well there. Again check with your local nursery and they will carry the species that grows there.

I fell both will grow there with care but the growth rate will not be the same as in native climates.