Urban Herb gardening
My house is located close to downtown Portland in NE just a few blocks from the I84 freeway down below. My front porch faces south and hence gets full sun. I assume its the best spot for rosemary,thyme, basil etc. Unfortunately the porch gets dusty I think partially from the freeway. Is there any danger in eating the herbs if they have been thoroughly washed? Do the pollutants get absorbed in the plant and therefore harmful?
Multnomah County Oregon urban horticulture
Thank you for your question to Ask the Expert.
You are wise to be concerned about potential pollution from busy roads getting onto your crops. Typically, concerns about growing veggies and herbs near transportation lines are with heavy metals and other contaminant getting into the soil and then eventually into the plants.
In this case, you will be presumably using purchased potting soil, which will not be in place long enough to pose a pollution hazard. The dust from diesel exhaust from trucks and trains, however may be drifting as far as your house. Is the dust that settles black and sooty? If yes, then avoid eating your crops from the porch. If not, then it could just be regular dust without contamination. If you were closer to the freeway, I would definitely advise against eating the produce. With four blocks of separation, it is likely safe to eat.
Regardless, if you choose to eat the produce, make sure to triple wash it before you consume it. Either rinse well in running water 3 times or immerse 3 times in cool water in a bowl or clean container and change the water between washings. Here is more information on washing produce: http://www.ext.colostate.edu/pubs/foodnut/09380.html
Please let me know if you have any further questions.