How deep to dig?
I have 5 almost-bare garden beds in the front yard that have extremely hard, compacted soil (probably from heavy house-building machinery). I want to grow some huge flowering trees (eg, Jacaranda mimosifolia and Magnolia grandiflora) along the front fence and some climbing roses along the side-fence. I can"t build up raised beds over the compacted soil because car doors will bang onto any retaining walls. I"m digging up and removing the compacted soil and replacing it with good soil and plenty of organic matter. How deep do you think I need to dig the compacted soil for proper plant roots to grow?