You've all heard of the past outbreaks of e-coli in romaine lettuce and other past cases of contaminated leafy greens.  The contaminants of those commercially grown leafy greens can also contaminate leafy greens you grow in your garden if you are not careful.  But you can avoid potential problems by following a few easy steps.

Let's look at the various stages of the plant growth where bacteria can contaminate your greens.  Bacteria can be found in contaminated water.  The University of California recommends that greywater NOT be used to irrigate edible plants.  The bacteria e-coli and salmonella can be found in the feces of farm animals.  If you add manure to your soil, you must do so in the fall prior to the planting season to allow any harmful bacteria to break down before planting, or else you run the risk of contamination. 

Live farm animals such as chickens and sheep should also not be allowed in the vicinity of your leafy green plants.  E-coli and other bacteria can live in the guts of these animals without making them sick.  But when they defecate, rain or other irrigation water could contaminate the soil.  The bacteria can then travel up the plant's roots as it grows.

Wild birds flying overhead can also contaminate leafy greens through their droppings.  If you have lots of birds regularly flying overhead, you may want to consider covering your edible leafy greens to protect them from potential contamination.

For additional information, check out –

Use of Graywater in Urban Landscapes in California, by Janet Hartin and Ben Faber.  University of California, Agriculture and Natural Resources. https://anrcatalog.ucanr.edu/pdf/8536.pdf

From Garden to Table:  Leafy Greens, by Esther McGinnis and Julie Garden-Robinson.  North Dakota State University. 

https://www.ag.ndsu.edu/publications/food-nutrition/from-garden-to-table-leafy-greens/h1754.pdf

“Leafy Greens Safety Guide,” by Kevin Loria.  Consumer reports, March 2020, p. 25 – 39.