>> Some people swear they will poison your food and you can drop dead by merely glancing at one in your garden.
Yes, I've read posts like that, mostly in the old DG site. I think there is no shortage of REAL things to worry about in life.
As a kid, I had DDT sprayed on me from the sky, and used a "DDT bomb" inside a Boy Scout tent every night for two weeks. So it's hard for me to take low-level exposure to not-very-toxic chemicals as seriously as some.
>> I guess the difference really is in the labor (energy) to handle and place all the blocks
Absolutely! I hauled my paving stones around gradually by buying no more than no more than one small trunk-load per day.
I try to keep my beds narrower than 36" wide, so I can reach everything from one side.
