Q.Will Planting A Tree/shrub Over Septic Drain Field Kill The Plant/shrub?
I am considering planting a Southern Magnolia near the septic drain field. Is doing this a death sentence for the tree (or any tree/shrub)?

Certified GKH Gardening Expert
More than likely. At least for a tree. It is not a good idea to plant anything that will extend deep roots into the area where human fecal matter will be present. (as well as the perforated pipes around the area) Human excrement is highly toxic, in most cases, and will not sustain for many plants or trees.
The exception will be that some grasses (and a few flowers) can tolerate septic field planting. The list is very limited, but you do have a few choices.
This article will help:
https://www.gardeningknowhow.com/ornamental/flowers/fgen/septic-field-plant-choices.htm