Question
We are on Long Island (NY).  Since we moved in to our home 4 years ago, there is a mildew smell in the yard in the early mornings and the evenings. I do not know what it is, whether it is a health hazard, or how to get rid of it. Any advice? I do not see anything unusual on the lawn.

Answer
I'm going to give this my best shot - but I have to warn you I don't think this is a gardening matter, even if it is happening in the garden more or less.  If you find someone more qualified comes up with a better answer, I'd go with their solutions.

So to begin:

Hi neighbor!

Can't say I have had this problem - not yet anyway - but mildew odors don't appear out of nowhere.  If it smells like a duck, it's a duck.

Whether it's a health hazard, well, I suppose there are people who could find this life threatening, but I am not one of them.  I do know that the Environmental Protection Agency announced guidelines on mold and mildew in 2001. That would be a medical question so I can't go there.  Plenty of civil cases have made it to trial based on mold that caused everything from stuffy noses and coughs to brain damage caused by mold.  The most dangerous of molds produce mycotoxins, chemicals made by mold that cause illness in people.

But where is it coming from?  Ah.... this is fascinating.

I refer you to a short but I thought relevant reflections on this subject at the Porter Paints website(www.porterpaints.com/products/techbulletins/tb16.pdf#search='mildew%20fungus%20conditions%20bathroom').  There, this paint company notes: "Heavy contamination by dirt and/or oils that provide both a food source for the fungus and a barrier between the paint and the organism.  This is the primary cause of mildew growth on quality paints."  If your door opens out on the North side of the house - usually the shadiest - and/or you are growing shrubs near the house on that same side, with excessive and constant moisture, you have conditions ideal for mildew.  Lack of air circulation contributes to the growth of any mold.

That Mildew odor may subside as the sun rises and lights up during the day (temporarily altering the environment, which had been dark and mildew-friendly).  If there is a Mildew problem, it would be important to find out where all that moisture is coming from.  It can't be good for your grass or any other vegetation.  It may be growing on paint surfaces, BBQs, outdoor furniture or floorcoverings, or all of the above.  There have been cases where insulation, buried within walls, was soaked and teeming with mold.  Depending where you are on Long Island, you could experience flooding every time the tide rises during a full moon while it's raining; mold is almost guaranteed.

To have experts test for mold, I would contact the American Industrial Hygiene Association (www.aiha.org/Content) for a local referral. It is my understand that AIHA members charge anywhere from $200 to $500 for their services.