“We want to eat what we grow, but not if we’re poisoning ourselves.”

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Another December Garden Haul – container garden in Takoma

“Dear PoPville,

In the back yard of my house in Park View, we have two square planters constructed of wooden boards sunk a few inches into the ground and packed with top soil. This past season (our first in the house) we had modest success growing basil, rosemary, cilantro, heirloom carrots, green onions and mint. We had planned to be a bit more ambitious in the coming season, thinking peppers, cherry tomatoes, garlic, onions, greens and more herbs.

But last week a garden specialist with RiverSmart Homes did a survey of the backyard at my house with an eye to helping us design some improvements. With respect to our planters, she warned that the soil quality in DC can get so bad in terms of lead and other contaminants that we were putting ourselves at risk by eating what we grew and could potentially cause significant harm to our not-yet-born children should we feed them from it.

Does anyone have any advice for soil testing and possible mitigation? I know how widespread backyard gardening is in this town, so I can’t believe we have to just give up. We want to eat what we grow, but not if we’re poisoning ourselves.”

38 Comment

  • I would be interested to know why they think DC soils are particularly bad.

    Unless your property was formerly an industrial site, there’s not much that goes on in a residential property that would cause soil pollution to the extent that you would have problems with vegetable uptake (as it relates to human consumption).

    Having said that, if you are growing in boxes anyway and you are worried about this, why not just use bagged soil?

    • Re. “why they think DC soils are particularly bad” — Older houses mean lead paint.
      .
      I’m not clear why the RiverSmart person didn’t think that the OP’s growing stuff in planters was sufficient. Maybe the planters aren’t very tall and there’s a risk that the plants’ roots could extend into the soil?

    • Leaded gasoline is the culprit here, not lead paint (well, lead paint probably contributes some, but pollution from leaded gas-burning cars is a much bigger culprit in urban areas).

      When we got our soil tested (I believe through UNC-Asheville, though I can’t confirm), we sent samples from several different areas of our yard. The only problem area was a patch of dirt to the side of the former garage site and right next to the alley. So that’s our flower garden; our vegetables are in the cleaner parts of the yard.

    • We got our soil tested by UDC earlier this year and it came back with lead levels so high that their test couldn’t read it so they sent it off to a more sophisticated lab for further testing, which revealed that our soil at a run-of-the-mill Petworth row house was >2.5 times the EPA limit for a residential property and we were sent a litany of educational materials that informed us that our soil is considered a health hazard to everyone who touches it and we should work with the Health Department or Cooperative Extension to implement lead abatement measures.

      • Sorry, AnonPetworth. That’s not surprising, but it sucks.

      • Are you now obligated to disclose this when you resell the house? Seems like a double-edged sword, if the tests come back positive. Yikes, indeed.

      • For what it’s worth we got some crazy results from the free UDC testing that were not replicated by other labs that we sent our soil to last year.

      • how do you elect to get your soil tested? It was going to be a 2016 goal of mine to start a garden in the back of the house I bought in 2014. I know there’s been lead found in our house and I’d LOVE to get my soil tested before planting….

    • “I would be interested to know why they think DC soils are particularly bad.” Because research has shown it.

      On top of the lead paint and lead gas issue already mentioned you have to worry about past contaminants. Was your house ever vacant and the yard used as a neighborhood dump? Did the past owner work as the neighborhood mechanic and dump all the waste oil in the yard behind his house? When it rains does your alley direct water into your yard? has your roof been directing rain water into your back yard for the last 50 years? All of this will deposit a lot of heavy metals and toxics into your soil. Most of which will build up over time.

      To fix it. Get your soil tested through UDC. They will tell you if it is safe to plant and eat what you plant. They might say its safe for some types of vegetables but not others. They may say it’s not safe for anything. If that is the case build raised garden beds that are cut off from the soil below. Or excavate the garden area and replace with clean soil.

      • “Because research has shown it.”
        Then please provide citations. I work in this field and now that we don’t use leaded gasoline anymore, the amount of airborne toxics that end up as soil contaminants are relatively small.

        Combined with the fact that most vegetables don’t accumulate large amounts of metals makes gardening pretty much a non-issue, unless you have reason to believe that you had something nasty (oil tanks, garbage dump) on your property in the past.

        Children playing in (and possibly eating) urban soils is a much larger vector than consuming vegetables from a back yard garden.

        • +1 it is the vegetable that you should be worried about it is the soil. Veggies don’t take up lead and arsenic very well.

          1. Get your soil tested and amend as necessary with clean compost (UDC or one of many labs you can mail samples too).
          2. wash your veggies thoroughly, especially those that come in contact with the soil.
          3. If led or arsenic levels are high don’t let kids play on it or eat it unless remediated.

  • University of Maryland Extension has information on their website on how local homeowners can collect a soil sample and send it to a nearby lab. Their website also provides information about possible concerns to residents, such as lead in soil.

  • Lead can seep into your backyard soil through years of deteriorating exterior paint, paint chips etc containing lead. All houses built before 1970 contain lead, it’s just a matter of was it abated? or encapsulated? and how well was that done. Getting your soil tested is helpful, but so is using a planter box and an impermeable membrane. Buying the soil you eat food from and making sure it’s not just the top layer is probably your safest best.

    • While this is true about lead paint, this would primarily be a problem if you are growing right next to your house or if your garden is down slope from the house.

      And even then, most vegetables don’t take up large amounts of lead (http://www.extension.umn.edu/garden/yard-garden/soils/lead-in-home-garden/) so unless you are eating the soil, you are probably fine.

      For reference, leafy and root vegetables are more likely to take up lead than say tomatoes, but still not a huge risk.

      • See above–next to your house is barely a problem; next to a roadway (including an alley) is a much bigger problem.

  • Yeah, the remedy is pretty simple, just buy plenty of bagged topsoil and replace the top foot or so of the boxes, 6 inches if you’re not growing root root crops (which, given the clay present in many places, would be hard to do anyway.) It’s a “$100, one afternoon and a pickup” kind of job, at most.

  • UDC used to do tests for free. They did ours and there were quick, helpful, and great. Looks like they are out of funds now, but that they will start again soon for free. http://www.udc.edu/college_of_urban_agriculture_and_environmental_studies/soil_testing

  • I also live in Park View and had my backyard soil tested six years ago when I bought my house. Just shipped off soil samples to the U. of Massachusetts, which does affordable soil testing, including for heavy metals. My soil tested as pretty normal, nothing that would scare me off from eating vegetables grown in it. I would go ahead and get your soil tested if you want to put yourself at ease.

  • I took a Master Gardner class a few years ago and was told to be careful about having your soil tested. Once you have the test completed you are obligated to share the information with the buyer if and when you decide to sell your property. Possible it is an urban legend

    • Well, real estates laws usually require the seller to disclose all known “material defects” in a property, so this could fall into that category.

    • If you find lead, I believe you are required to report it when you sell a house. Don’t think it’s much enforced as in most cases there’s plausible deniability. A huge majority of houses in DC have lead paint or other remnants, so I actually take it as a good sign if folks disclose lead – all it means is that they’re paying attention.

  • I would definitely get the soil tested, it’s relatively easy. My soil is contaminated with lead and other heavy metals due to traffic and the long-time presence of a heating oil tank that leaked substantially in its later years of disuse. The only things I grow directly in the soil are decorative, my veggies and herbs are in pots.

  • It also depends on what you’re growing. A lot food crops don’t uptake the contaminants in the soil.

  • Sadly, lead in soil (from paint chips via lazy renovators prior to our ownership) is something I’ve learned a lot about recently. Do your research – there’s a lot of info out there – but my understanding is that there’s a lot more danger in lead dust contamination (from people/pets tracking soil indoors) than from lead content in plant matter. Plants don’t leach that much lead. To be on the safe side (and because it’s just better for growing) we fill our raised bed with free compost from the Ft. Totten Transfer Station. If you get your soil tested and there’s significant lead contamination, there are several options, but if you can afford it I would opt for hiring a contractor to remove several inches of soil, then replace with fresh soil & new sod. We had this done recently. I wish I could recommend our contractors but they were kind of asshats. Anyway hopefully it won’t come to that for you. Best of luck!

    • ETA: I am just now realizing that I actually have no idea what controls are in place for free DC compost, so maybe that’s not a perfect option. We eliminated our raised bed this fall anyway so moot point but just to note. Also just going shoe-free or having special shoes for using out in the yard could make a big difference, esp. if there’s an expectation of rugrats anytime soon.

  • *shoe-free in the house, not outdoors! Okay I am stopping now. Lead gets me fired up.

  • You can send your soil for testing, but it’s also pretty easy to bring in dirt for new beds. Just dig down a few inches then lay down some landscaping cloth. For a small bed you can buy top soil and compost at Home Depot. For larger beds you can get a truckload sold by the yard from a number of gardening centers. Most will pre-mix your desired ratio of organic compost to top soil.

  • I had my soil tested last year when UDC was offering free testing. Both my back yard garden and community garden had good healthy soil.
    If UDC isn’t offering their free testing, I’d recommend UMass Amherst.

  • Thanks everyone. We’ll get the soil tested and take it from there. I’ve no problem at all if it comes to it with digging out the soil already in the planters, disbursing elsewhere in the yard (for example to patch holes in my lawn and fill out flower beds) and replace it with new top soil.

    • Leaf Gro is a good soil amendment – you can buy it by the bag (Johnson’s, American Plant Nursery & more) or in bulk.
      It’s also useful to add lightweight potting soil – like Berger BM1 all purpose mix- to your topsoil. Or make your own mix (search Cornell soil-less mix)

    • I posted a suggestion above. I’ll just add that the native soil is not particularly rich in any case. You’ll have a lot more success with your plants if you start with good soil and maintain it.

  • Love & Carrots will do a soil inspection as part of a consultation if you’re considering have them design and/or install a garden be it raised beds or a pollinator garden.

    • This is what we did- turned out our soil was pretty terrible…so they removed a # of inches of contaminated soil, put in good soil- added raised beds/veggies & an herb/pollinator garden, plus drip irrigation…amazing results! Highly recommend L&C.

  • When I set up my backyard planter beds, I was told to make sure I had at least 18 inches of fresh soil. If your planter is only one board deep, yeah, that’s probably not enough distance between your vegetables and possible contaminants.

  • I would be very leary of anyone trying to scare you about soil quality while also offering to sell you a solution. I’d also be interested in any test results for harvested food, not just the soil.

  • UMass extension does it. It is super easy to mail your soil in and the total cost is $15.00.

    http://soiltest.umass.edu/

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