Is My Garden Toxic, And What Can I Do About It?

Photo by Adrien King
Photo by Adrien King on Unsplash

Growing your own vegetable garden should be a source of enjoyment and health. Unfortunately, we face the danger of having our soil contaminated by toxins and other substances. Too often we have to ask ourselves: “is my soil safe to grow vegetables?”

There are many ways soil can become contaminated. Potential contaminates are construction sites, roadways, manure, pesticides, herbicides, fertilizers, garbage, and many everyday items that we commonly use in the garden. These contaminants can sometimes be taken up by the food we grow and make us sick when we ingest them. Have your soil tested by a laboratory if you are concerned in any way. Thankfully, there are ways to make your garden safe again, such as remove sources of contamination, be cognizant of our soil type, add lots of organic matter, and replace the soil.

In this day and age, so many products produce adverse effects on the environment. Here are some ways your garden can become a toxic space and what you can do about it.


What Can Make My Soil Toxic?

Unfortunately, there are many things that can leach toxic chemicals or other contaminants into the soil. Some of these come from the manufacturing of certain products, and sometimes the products themselves can make their way into the soil or water. Some of them are the byproducts of industries that we little control over, but some of them we introduce ourselves. Toxins can be absorbed by a plant’s roots and, depending on the concentration, can make it into the food we eat (naturally, root crops are most susceptible). They can also reduce fertility and decrease yield.

If you are unsure if your soil is safe, or think it might be contaminated in any way, it is best to get your soil tested right away. You can send a soil sample to a laboratory for a detailed analysis. This can usually be done for a minimal fee, and the cost will be well worth the peace of mind. Check with your local government, university, or environmental organization to find a lab in your area that deals with soil contaminants.

Here are some key things to watch out for that can contaminate your soil.

  1. Construction sites
  2. Roads, vehicles, and petroleum products
  3. Manure, human feces, and purchased soil
  4. Lead and other heavy metals
  5. Pesticides, herbicides, and fertilizers
  6. Garbage
  7. Everyday items we use in the garden

1. Construction Sites

Construction sites are a potential source of contaminated soil. Modern building processes are not like the barn-raising days of old, and many chemicals and toxic substances are used. Even with consciences companies, chemicals can get spilled and things can be dropped or left in the ground. These can all be potential sources of toxins leaching into the soil.

If you live near a construction site, take care that nothing is being dumped or spilled near your garden site. It might also be a good idea to talk with the site foreman to let him know that you have a vegetable garden in the area, and make sure they are taking appropriate measures to clean up their workspace.

This is also true if you have just moved into a new area, or into a recently built home. It is probably a good idea to have the soil tested before you plant your vegetable garden, just to make sure there is no lingering residue from construction in the ground.

2. Roads, Vehicles, And Petroleum Products

Photo by Varun Gaba on Unsplash
Photo by Varun Gaba on Unsplash

As cars drive by your garden, they can sully your home-grown goodness with asphalt particles, exhaust, and petroleum products. Any of these items eaten in large quantities are toxic, but the vegetables from your roadside garden are probably safe. Studies have been conducted testing contaminants on vegetables grown on roadsides and have found little, if nothing, to worry about. It is suggested, however, that you rinse your vegetables prior to consumption to wash off anything thrown on them by passing tires.

The use of lead in gasoline has been banned for years, but if you live in an older area there might still be traces from old residue in the ground.

If you live or garden in a high-traffic area, it is probably worth getting your soil tested, especially if you notice an excessive amount of oil or gasoline that has been spilled on the road.

3. Manure, Human Feces, And Purchased Soil

Manure is one of the greatest gifts we can give to our garden, but it can be a source of toxins. Manure that has not been properly composted can contain harmful pathogens that can be passed onto your vegetables. If you are buying manure for your garden, make sure it is well-rotted.

Buy animal manure from a reputable place, preferably an organic farm where you can talk directly to the farmer. Many pesticides and herbicides used on conventional farms will pass through an animal’s intestines, and even survive through composting. If the manure is spread over your garden, it can leach into your soil and might even kill your vegetables.

The same can be true for purchased soil. Bad soil will cause problems in your garden for years to come so choose carefully.

Manure by Carmen Edenhofer
Image by Carmen Edenhofer

You have to be especially careful with human feces which is becoming a very popular source of plant nutrition. Humans are very inefficient creatures, and this is also true of our digestive tract. Pathogens abound in human feces, so if you want to use your own (or someone else’s) poop in your garden, make sure it is VERY well composted.

4. Lead And Other Heavy Metals

Lead and other heavy metals can end up in your soil from a variety of sources. We have already talked about the potential dangers of growing near roadways, and another source that can linger from bygone days is paint. Lead paint was very popular for exterior paint, and it might be something to look into if you live in an old house. If you live in an old agricultural area, especially near an old orchard, you might have lead and other heavy metals in your soil from now-banned agricultural chemicals. Many heavy metals do not wash out of the soil, nor are they biodegradable. As a result, they will linger in the soil for thousands of years.

Unfortunately, even our air can be a source of toxicity to our gardens. Air pollution can deposit heavy metals into the top few centimeters of the soil, so this might be a concern if you live in a highly populated area.

5. Pesticides, Herbicides, And Fertilizers

Pesticides, herbicides, and fertilizers are deemed safe for use in our food. However, not only do these products poison our food, but they also stay in the ground and poison the soil or wash into our groundwater. There are many ways to garden without pesticides and herbicides, and they should be avoided at all costs. However, we have no way of knowing what our predecessors did before us, so it might be worth checking to see if these chemicals are still in the soil.

Growing up in the city, I learned from an early age that you never walk on grass that had yellow signs posted. These were the signs indicating that herbicides had

6. Garbage

Most places have rules about what cannot be thrown in the landfill. Even so, it is shocking what actually gets dumped there. A lot of this garbage leaches chemicals into the soil. Where I grew up, the old city dump was filled over and new neighbourhoods built on top. While this seems like useful land use, I wonder what the long-term soil health will look like.

7. Everyday Items We Use In The Garden

Many everyday items that we use are a potential source of toxicity to our soil. Treated lumber is very attractive for its long-lasting qualities but it is made from many different chemicals which are very toxic and leach into the soil. Tires make good containers since they are free and heat up the soil but are made from numerous chemicals and metals. Plastic also leaches chemicals into the soil.


What We Can Do To Clean Up The Soil

Thinking about all the different things that can poison your garden can get a little depressing. but there are things we can do about it.

Obviously, the first thing is to not use anything that we know is a potential source of contamination. You can also assess the type of soil you have and plan accordingly. Clay tends to hold onto toxins that would otherwise wash out of sandy soil. Maintaining a neutral pH can diminish the negative effects of the contaminants.

The most natural method to improve contaminated land is to build up your soil with organic matter. Valuable compost and rich humus do not remove contaminants, but it allows the soil to process certain toxins and disperses the rest so they are less likely to be absorbed by your vegetables. In the end, the safest route is to completely remove and contaminated soil, and bring in fresh clean soil.


The modern world is full of man-made products and chemicals that build up in the environment. While it is impossible to escape from these sources of potential toxins, we shouldn’t let this stop us from growing good, healthy food. We do what we can to minimize them in our gardens and in our lives as we strive for self-sufficiency.

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About the Author Harry Thompson

Involved in home renovations throughout his life, Harry is an expert in everything to do with home and garden DIY. In his spare time, he enjoys cooking and tending to his garden.