what kind of samll trees for back yard

Hi, please recommend what kinds of SMALL trees for back yard near fence wall in Irvine?

HOA does not allow big trees.

Somebody mention Purple Potato Tree, is it good?
Any other recommendation? 

Enjoy the cool down weekend!

dwarf variety (6ft) or semi-dwarf (10ft).  I prefer semi dwarf.

Lime tree (thornless)
meyer lemon
Kumquat
orange

You can find these at Home Depot or Lowes for $29.

Try Little Ollie or Magnolia tree