Wednesday, April 22, 2015

Food Safety Biology 101 for the Home Gardener

Last month I discussed three types of hazards that can occur anywhere along the food production process including during the growing, harvesting, handling, storing or serving of fruit and vegetables. These include physical, chemical and biological hazards. Today’s post will explore biological food safety risks that can cause foodborne illness or what’s commonly referred to as food poisoning.

Food poisoning is caused by tiny living organisms called pathogenic microorganisms. These microorganisms can be either bacteria, for example Salmonella or E. coli, a virus (like norovirus) or fungal in nature like the mold that grows on an old cucumber that sat in the fridge for too many days. Parasites, like Giardia, can also cause foodborne illness. Microorganisms are found throughout the natural world and even on the food we eat. However, some microorganisms are more dangerous than others, and when given favorable conditions they can multiply to levels that can make people sick if ingested. Therefore as food gardeners it is important to know how they are introduced into the food system and the conditions that favor their growth.

In the garden environment these microorganisms are most often introduced through either soil, water or poor hygiene on the part of the gardener. In soil, the original source is almost always fecal matter. This can be from an animal like a cat or a raccoon leaving droppings in the garden.  In farming, it is recommended that farmers not harvest produce within a 5 foot radius of an animal dropping. I follow this practice in my home garden too. Last year I did not eat from one of my raised beds because my dog did her business in there.  The feces of both wild and domesticated animals can harbor serious pathogens and must be removed.  It is important to protect yourself when you remove these feces and take precautions like wearing gloves. Ideally you will have fencing to keep animals out of your garden. (I'm adding another raised bed this year to this section of my yard and some fencing!)

Pathogens in soil can also come from manure that has not been properly composted.  If I use manure I get it from a commercial source. Certainly many people use manure from their local farmer in their vegetable garden without incident. However, there is no way to know if the manure is 100 % safe unless it is commercially processed. If you are going to use manure from a farmer friend in your vegetable garden, it is best to use it on crops that will be cooked before eating. 

Water is another part of the garden landscape where microorganisms can exist and grow. Standing water is your greatest concern since this presents a favorable condition for microorganisms to reproduce. This means that you should avoid watering your vegetable plants with water from rain barrels or ponds. Remember, only use potable water you would be willing to drink.  It is also important to make every effort to avoid standing water in the form of puddles in your vegetable garden. Lastly use watering containers that you can wash regularly. Would you drink from a cup that’s been sitting outside for three weeks? Probably not. For the same reason you want to make sure your water your plants from containers that are clean.

Good hygiene practices are another essential aspect of keeping your garden safe. Always wash your hands before harvesting or handling plants and wash your gardening gloves regularly. On a similar note use clean and sanitized harvesting containers. I harvest my vegetables in plastic bowls that can go into the dishwasher or I use reusable clothe grocery bags that can go in the washing machine. One more good practice is to never work in the garden when you’re sick. Always wait at least 24 hours after symptoms of (diarrhea, vomiting, fever) have subsided before returning to the garden.

Proper storage and handling of produce is also key to preventing food safety issues. That will be the focus of next month’s blog post.


UMD Extension. Pet Waste and Water Quality. Though this is about water quality it provides some safety issues with regards to pet waste and advice for cleaning it up).

Cornell Extension.  GAPS: Wildlife and Animal Management. This article is designed for farmers but provides great advice on preventing and dealing with animals in the food growing environment.

Maryland Department of Agriculture. Maryland’s Manure Resource Page.

University of Wisconsin Extension. Safely Using Produce from Flooded Gardens. I mentioned standing water is a food safety risk. This article goes into much more detail about this and specifies what can be salvaged if your garden is flooded.

University of Maryland Extension. Hand Hygiene 101. Check out the tab on the left for more food safety tips!


  1. Wow, Lisa, I'd never thought of some of these things. Thanks so much for writing this series!

  2. I'm glad you find it useful Lena :-) I love having the chance to combine my love of gardening and microbiology through these blog posts!


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