Sorry, I cannot offer you any worthwhile info on disc'ing your planting beds. I've been dealing with my own home maintenance issues, but I believe I've gotten to the root of it.
I did the demo for a new bathroom (this one) about a dozen years ago, so I assume the issue 'took root' and has grown since that time.
Complaints about a slow to-flush toilet were made, and I promised to look into it. When a 'snake' cable didn't clear it up, I advised the occupants, "I need to remove the toilet, and see what's going-on." Off came the toilet, and I sent someone to the store for a wax ring. When they came-back, my 11 year old grandson told me, "
Grandpa, they don't sell wax rings anymore, that's old fashioned!"
When I found this obstruction, I was trying to decide how-embedded it was when I grabbed a pair of Craftsman slip-joint pliers and gave a tug. Much to my surprise, it came smoothly out, and there was no further root infestation below where this ran. With the commode once-more mounted, it was 'smooth-going.' Or so I'm told.