Limestone and concrete are both alkaline, and they will raise soil pH over time. This is an issue if you are growing blueberries or something that requires acidic soil. Most plants do fine with soil pH between 6.5 and and 8, and for these plants, a limestone edge would have little adverse effect. I grow raspberries in our native soil, pH = 7.6, and sometimes I water the bed with our tap water, which also has pH = 7.6. The raspberries are healthy and vigorous.

Don't worry about it. The amount of lime leaching into your dirt from edging stones is tiny compared to the amount coming from the limestone rock under the garden, and the alkaline water from the ground.

Thanks peeps!

Agree - for agricultural purposes, you can practically consider anything larger than 1/10" insoluble.

Al