Budgie Aviary What Kind Of Trees Are Ideal To Be Grown In A Cockatiel And Budgie Aviary?

What kind of trees are ideal to be grown in a cockatiel and budgie aviary? - budgie aviary

I have an aviary with breeding cockatiels and budgies, and I would like to use in a few trees or shrubs, etc. for the birds on real and existing routes.
Ideas welcome