Where Does the Mold on Bread Come From?

When bread is old, it develops a furry, green or gray coat called mold.

moldy bread in a ziplock bag

Mold is actually a patch of tiny plants which grow more rapidly than the weeds in your garden. Since no one “plants” this mold on the bread, where then does it come from?

The plant’s spores, which are its reproductive bodies, float around in the air until they find some place to land.

They are too tiny to even be seen when they are floating about. But when they land, usually on warm, moist bread, they begin to grow just like seeds do in warm, moist soil.

As they grow, they send more spores into the air and onto the bread as well.

Each tiny mold plant, when seen under a microscope, has two branches, a longer one with little black balls (the spores) and a shorter one, which acts like a root, penetrating into the bread and absorbing food.

Interestingly, a mold’s diet is quite varied.

Not only will it grow on bread, but also on meat, vegetables, and even shoes, clothes, and books if they’re in warm, moist areas.

A mold, similar to the one found on bread, is grown in special tanks by scientists and produces one of the marvels of modern medicine, penicillin.

Read more about mold safety and health impacts here:


About Karen Hill

Karen Hill is a freelance writer, editor, and columnist. Born in New York, her work has appeared in the Examiner, Yahoo News, Buzzfeed, among others.

23 thoughts on “Where Does the Mold on Bread Come From?”

  1. What is the actual one that it grows on the best ( Meat, Bread, or Vegetables)?
    is the fact that it grows on shoes and the other things actuly found with mold or was it tested or do you just know from someone that told you that it grew mold on SHOES!!!!!!!!!!!!:):):) don’t ask me why I ask this!!!!!

  2. Why does mold grow?? I too, did a science fair project, and I found that the rye bread develops mold the fastest. I was wondering why, and it would be great for some answers. Thanks, ~Anonymous

  3. Considering how fast mold grows on bread let alone tile on a shower no one should be suprised how hary it is. Mold spores can stay dorminant untill water makes them grow. You can spread mold around if your not carefull when your cleaning it. It can be harmfull and helpfull it all depends on the strain.

  4. Mold can grow almost any place as long as it has moisture. It can be dormint for years and then grow when it gets wet. One fact that amazes me is it can be harmfull and helpfull it all depends on the strain of mold.

  5. just because im allergic to penicillin means i can die from shock dont mean you get to brag it all over the place i got my speacial needs down here at texas too!!!!!

  6. did u found out how many days — for the mold to start showing…… my project in due soon —2nd week in december —on my 7 day now with this project do i have enough time…….. someone please reply

  7. Okay so help. How long should it take mold to grow, I have been doing a science experiment for 10 days on moldy bread and no mold has grown.
    My science project is due soon so help.

  8. You’re right that mold is not a plant, but it is not its own kingdom. It is part of the Fungi kingdom which also includes the likes of yeasts, mildews, mushrooms, etc.

  9. there are mold spores (they r like little bubbles, except u cant pop them) and they float around in the air so small, that u need a good microscope. the mold spores r kind of like tape, they stick onto things, usually food such as bread, or strawberries. i hope this helped u because i know how it feels when u r looking for something, and never can find it. :(
    P.S. i am not an adult, cause i may sound like one, just so u know.

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