I have several questions about my home garden. I really enjoy gardening and am in my 40s, recently diagnosed with cancer and so safety has been in the forefront of my mind. My neighbor came over to my home, looked at my vegetable and berry garden, and said "I would never eat anything that comes out of this ground. Especially since you have cancer issues. It's in a runoff area." (My cancer started before I moved here). As you can see in the picture, my garden is located towards the bottom of a hill and would gather runoff from the yards above it with rains.

My questions are several:

1) Is my garden unsafe given its location - "in a runoff zone" of my neighbor's yard?

2) We collect roof runoff rain water in a barrel and have been using it for a couple years to water the plants. Is this safe? I have seen conflicting data. I am less worried about bacteria and more worried about carcinogens. I believe we have asphalt shingles.

3) In regards to safety only (not garden vigor), is there a type of mulch that should be avoided? I want to avoid CCA based mulch?

4) Given all this, should I test the soil for heavy metals or pesticides and if so, what testing would you recommend and by whom?

5) I also have a couple fruit trees beside the garden. I guess the same questions would apply to them.

Basically is it safe to eat food grown in my garden (fruit, berries, and vegetables)?

We're trying to do everything right, but cancer is no joke and it seems impossible to do in this day and age.

Thank you!

Nathan

Columbia, Howard County

Hello Nathan,

While stormwater runoff can certainly carry pollutants of many types, we do not think it would be a major concern or risk in this setting. Plus, as the water moves through the soil profile (granted, some runs along the surface before soaking in), the soil and plant roots will be filtering some of it. Adding plants along the property line to help buffer this runoff, both for erosion's sake alone as well as reducing any contaminants, may be worth considering. Unfortunately there are probably an equal or greater number of pollutant sources separate from anything in the runoff that we doubt it's a significant contributor to health risk, especially in a residential area compared to, say, a more industrial/commercial or agricultural development.

The location of your produce beds looks fine to us, though perhaps a bit shady, although it's hard to tell this time of year due to the sun angle. The majority of vegetable and fruit plants require full sun (6-8 or more hours of direct summer sun) to thrive, though a few will do reasonably well with partial shade. Soil drainage, which keeps the root zone well-oxygenated enough for plant health, is also very important, but as long as any runoff water seeps into the soil profile quickly enough that after a heavy rain the garden beds are not too soggy, this feature is probably also fine. (If it does skew wet, you could try raising the beds up higher by making the sides deeper so the planting level is at a greater height above the surrounding grade.)

While we agree that there can be conflicting information about roof runoff water, in our opinion, it would be safer to not use it on edible plants, but using it to water ornamental plants (anything not harvested for food) should be fine. There are many factors that affect the quality of collected water – roof composition, animals on the roof, water storage conditions, etc. Bird or squirrel feces on the roof, for example, could contaminate the rain barrel water. These references below might be of interest:

• Limited studies have been done on rain barrel use for food crops. A study done by Rutgers University has recommendations: Rain Barrels Part IV: Testing and Applying Harvested Water to Irrigate a Vegetable Garden
• Here is a study on the topic done in Philadelphia: Assessment of Water Quality in Roof-Harvested Rainwater Barrels in Greater Philadelphia
• Here's information on a citizen scientist project that began a few years ago to look into the safety of using rain barrel water (see link).

It becomes a personal choice based on your level of comfort. Using potable water (city or well water) carries less risk than rain barrel water. If you do decide to rain barrel water, we'd recommend you water at the base of the plants, right into the soil, to limit contact with edible plant parts, such as leafy greens. Avoiding extra leaf wetness also helps to prevent plant diseases, regardless of water quality. If you are not comfortable using it on your edibles, feel free to water your other flowers and landscape plants with rain barrel water. We realize you're more concerned with carcinogenic residues versus microbes, but the microbial content might still be a risk if someone is immunocompromised from treatment.

Regarding the use of a disinfectant, Rutgers University recommends the following:
Rain barrel users should make sure to clean the barrel with a 3% bleach solution before collecting water to irrigate a vegetable/herb garden. Household, unscented bleach with a 5–6% chlorine solution can be added at the rate of one-eighth teaspoon (8 drops) of bleach per gallon of water. A typical 55 gallon rain barrel would need approximately one ounce of bleach added on a monthly basis. During periods of frequent rainfall, bimonthly treatment may be necessary. Wait approximately 24 hours after the addition of bleach to allow the chlorine to dissipate before using the water. Note that household bleach is not labeled for use in water treatment by the Food and Drug Administration although it is frequently recommended for emergency disinfection of drinking water (USEPA, 2006b).

Mulch would not contain CCA treatments, which were discontinued around twenty years ago (in lumber...they were not in mulch anyway unless it was made from ground-up pallets or other recycled wood). The only mulch that we think could (but not necessarily would) have concerning residues would be the dyed types, which use recycled wood more so than actual bark. Shredded hardwood bark, pine bark, pine needles, leaf litter, and arborist wood chips are all suitable organic mulch choices that break down into good soil-enriching organic matter.

We do always recommend soil testing for the basic nutrient and acidity (pH) analysis, plus for lead (other heavy metals may also be an optional add-on, depending on the lab), when growing vegetables and fruits. Lead contamination is less a risk for plant absorption and more of an issue of lead-tainted soil dust coating harvested greens or fruits. This is one reason why it's always recommended to rinse produce off well before consuming it, even with home-grown plants. Our Soil Testing and Soil Testing Labs page includes a list of suggested labs you can choose from, and we can help to interpret the results if desired. Note that some level of non-zero lead presence is to be expected in basically any human-developed area, but as long as it's below the threshold for risk, remediation efforts would not be needed. Depending on how busy the lab is, results may take 2-3 weeks to arrive.

Fruit trees are high-maintenance crops compared to small fruits (berries) and vegetables. They require specialized pruning, routine pesticide use (even if organic) to prevent problems that could harm tree health or ruin a crop one year, and fruit thinning and other seasonal tasks. If you prefer to avoid any type of pesticide use on the trees, be aware that you might not get usable fruit every year. Some fruit trees require compatible pollinators in order to produce a crop, but if your trees are well-established already, this might be something you have already addressed. We have recently revised our fruit page content, and you can find pages about specific fruits (some are lumped together if their care is similar) and their care and troubleshooting in the linked page.

In short, while there are unfortunately a plethora of health risks in modern times (PFA "forever chemicals," micro/nanoplastics, air pollution particulates, and so on), in our opinion, any contaminants from a home vegetable garden grown with responsible (following label directions) or minimal pesticide use is unlikely to be a significant source of a health risk, and probably even outweighs any risk to some extent with the benefits from harvest quality/freshness of fresh-picked produce.

Miri

This was incredibly helpful.  

If sun in the morning is lacking but the rest of the day is essentially full sun, that should be plenty.

A steeper slope might increase runoff, but that also depends greatly on how well-vegetated it is. (Are there many areas of bare soil that erode? Or do plant roots secure most of it?)

For the property line planting, does that area also receive full sun (or mostly sun), or is it more shaded? Plants won't be "thirsty" enough to necessarily absorb extra water, but wet-tolerant species can be chosen if you think that the location stays wetter due to drainage of the area plus any added runoff. By itself, the goal of plantings isn't necessarily to dry out that spot, just help hold soil in place with their roots while filtering the runoff (as any plant could contribute to). What mature size can they reach without having to rely on pruning to keep them restrained? (What would be the max height and width?)

Dyed mulch isn't as much of a concern regarding dye materials as potential contaminants (given that CCA-treated wood is less likely to be included, though we can't rule it out). As you noticed, since it uses recycled ground-up wood, other materials might accidentally wind-up in the mix. You can use any organic (as in biodegradable) mulch type on fruit trees, just make sure that the layer isn't thicker than about three inches deep, and it is not piled up against the trunk or root flare. This mulching approach applies to all trees and shrubs, not just fruits.

Soil testing can be done any time of year and there is no ideal time (other than maybe having the lab be less busy), both prior to planting and every few years thereafter to monitor conditions like nutrient content, acidity (pH), and organic matter proportion.

Miri



Oh, and staying on the theme of safety, for my garden soil, is there a specific type of soil I should be using?  I’ve been using a lot of miracle grow garden soil, as well as adding topsoil.

Hi Nathan,

We can't say with any certainty what will be "safe"...there are too many variables and, of course, plenty of unknowns that can affect short-term or long-term human health. We can say that anyone who uses a pesticide is bound by law to apply it in a way consistent with the product labeling, and when used as directed, the chemical should be as low-risk as the ingredients can be, both for people and the environment. Many pesticides degrade once they interact with either direct sunlight, rain, soil microbes, soil chemistry, and other factors. 

ou could inquire with any neighbors about their use of pesticide and try to convince them to reduce use if needed. It's not just uphill runoff that might be of concern, since drift (the movement of a pesticide away from the treatment site) can occur with both water flow and wind (including evaporation, if applied when it's too hot out). We're not trying to scare you, just make you aware that there may not be one source of potential pesticide movement from a nearby property. Any fertilizer or other chemicals the residents might use also would tend to stay on the application site unless over-applied or applied in a manner not consistent with that product's labeling. Unnecessary fertilizer use can waste resources and someone's time and money, potentially polluting stormwater runoff that enters streams and the Bay, but by itself it's probably not a significant health hazard.

You can explore what comprises a Mulch and Soil Council certification with the information on the organization's website. The description implies they are screening for CCA-treated wood in mulches. A few bagged mulch brands include an herbicide to suppress weeds, but that information (like the herbicide active ingredients) will be included on the bag label.

We encourage you to explore our soils, compost & fertilizer topic web pages, as they include an introduction to basic soil types, soil amendments, and organic matter in soils as it relates to plant and soil health. A certain percentage of organic matter in the soil helps it retain moisture, nutrients, and support beneficial microbe populations. If an amendment is needed at all (it won't always be, at least for decorative plantings), compost and perhaps good-quality topsoil tends to be the type of supplementation used. Even then, the goal is to amend the existing soil just enough so that the new material helps it "fluff up" and be more airy and less compact, which improves drainage. Any added soil should be well-mixed into the existing soil so the roots aren't growing in one soil type adjacent to another, since they can hold and release moisture at different rates. A uniform soil texture in the root zone of plants is ideal for minimizing root stress and maximizing growth. Avoid rototilling the two together if you can help it, though, since tilling can damage soil structure, an important component of soil health. (You can learn more about this in the group of pages linked above.)

Extension doesn't collect information on soil/mulch/compost brands, nor to we make particular product recommendations, but anything that does not contain fertilizer is best, since you want to add only what nutrients a soil test shows are needed. Some brands, like Miracle-Gro, make both potting mix and in-ground mix soils, and they generally should not be used in the opposite setting since that can impact their performance. (That is, avoid using a soil blend meant for use in the ground in a pot instead, and avoid using potting mix meant for containers in the ground instead, because the two differ in water-holding capacity.) For example, despite sometimes being labeled "potting soils," potting mixes don't contain actual "true" soil (sand, silt, or clay components); good-quality topsoil does, though it tends to have more organic matter content as well (a good trait) compared to more fill-dirt grade topsoil.

The main focus of soil should be sufficient drainage based on the root wetness tolerances of that plant, since if that need is met, along with the plant's sunlight intensity requirements, the nuances of soil conditions and type tend not to factor too heavily into plant performance and the yield of vegetables or fruits. If drainage is poor in a particular spot, it will be far simpler to try relocating that planned planting to an area with suitable drainage rather than trying to fix the drainage to accommodate those plants. (Putting in alternative species that handle poor drainage well is the ideal in that case, but few of them will be fruit-bearing, so they would be more serving of pollinators or other wildlife.)

Miri