Raised garden beds on blacktop

Asked January 12, 2018, 7:11 AM EST

Hi, I'm wondering about any research found on how much/what chemicals leach into plants planted in raised beds on asphalt. I am asking about a space with some existing beds that I do not believe have liners at their bases and am wondering about the viability of that soil moving forward as well? I've read that putting in a liner and pea gravel with drain holes is the best option for new beds on asphalt- would you agree? Also, if we dug up the asphalt, could we plant directly into that or would that soil be contaminated- if so for how deep would you recommend digging the soil out and replacing? Any other info suggestions I should consider? This is for a possible community garden space- 18 existing beds- looking to double the size. Thanks for your time

Ramsey County Minnesota ashphalt

1 Response

I think putting in a liner and pea gravel underneath, is an excellent thing to do. Raised beds on ashphalt may need more drainage than they would get sitting on ashphalt especially if we get a repeat of the torrential rains we get some summers. The soil under the ashphalt will be very compacted and unsuitable for gardening.
These references may be helpful.
http://cwmi.css.cornell.edu/Soil_Contaminants.pdf