How deep should soil be for a sunflower bed?
Due to circumstances, I'm wanting to put in a row of sunflowers to make a short term privacy border (which may mysteriously reappear next year/s as well). The problem is the existing soil is:
A) scraggly lawn
B) poor in general and very rocky
Given this, I'm likely going to have to rip out a line of sod then try to fill and build up actual dirt. Actually hauling in dirt is going to be an effort, and I'll try to improve what I have. What would ya'll say is the minimum for sunflowers? I just need a starting point. Expected size is ~20'×1'