It has recently come to my attention that working with potting mix comes with some health risks that no one has ever told us about. Because the soil is typically stored in a plastic bag — often in the sun — it provides the perfect breeding ground (warm and moist) for bacteria and fungi. Normally, this wouldn't cause a problem, but when that bacteria is legionella bacteria, it can lead to legionnaire's disease, a potentially fatal form of pneumonia.
Reports of deaths from legionella bacteria are primarily from Australia and Japan, but are not unknown in the United States, explains a 2000 CDC report.
A July 2017 report by the CDC also lists commercial bags of compost as a possible source of the legionella bacteria. Some commercial potting mixes (and compost) tested in the US have tested positive to legionella bacteria, the CDC further explains.
While the risk appears to be higher in Australia where 73 percent of the soil samples tested contained legionella, gardeners in the U.S. should be aware of the risks associated with opening and using bags of potting soil or compost.
How do you get Legionnaire's disease?
It is believed that inhalation of the bacteria is the primary means of infection, but the CDC has not ruled out contact with the skin.
Who is at the greatest risk?
People with respiratory disorders, such as COPD, those with compromised immune systems and the elderly are at the highest risk, but that doesn't mean it can't infect younger and healthier gardeners, too.
How do you prevent contamination?
Observe the following recommendations to reduce the risk of exposure to the legionella bacteria.
I'm certainly not recommending that you avoid potting soils and compost completely, but never hurts to be cautious, especially if you are at a high risk due to health and/or age.
A couple of years ago my daughter gave me an AeroGarden for my birthday. My plants grew like a charm. First, I grew peppers and then I grew tomatoes and I even grew herbs.
Then . . . I moved.
When I set the AeroGarden up again it just didn't grow very well. I thought I had damaged it during the move. I changed the water and scrubbed out the basin. I replaced the air stone. I checked that the pump was working. The lights looked fine, but my plants still weren't growing as they should.
I planted new seeds in new pods.
My seeds didn't germinate well and when they did, the plant growth was stunted. Many of the leaves developed brown margins.
I was puzzled, until I visited the AeroGarden site.
According to the site, my well water might be the culprit. Apparently hard water can prevent germination and cause both stunted growth and browning leaves.
Once again, I emptied the basin and scrubbed it clean. This time I filled it with filtered water. Within days my seeds germinated and showed signs of vigorous new growth.
I am growing petunias and lemon basil in it now. I can't say for sure how long ago I planted the petunias as I forgot to reset the 'days planted' counter. I know that I planted them after Christmas. That means they can't have been growing longer than 40 days or so.
I am so excited to have solved the problem and to have petunias blooming inside as the snow falls outside!
If you are having issues with your AeroGarden, or similar hydroponics unit, try using filtered water instead of your well water. It solved my problems. I hope it solves yours too.