I left a cup of tea with Lemmon on my desk and after a while green mold start growing on the water. From my understating this is Penicillium digitatum. I gave it some sugar and after one day black spots appeared. I read that it can be little bit dangerous to inhale mold so I wrapped the cup with saran wrap and make some holes in it in order to give the mold oxygen.

  1. What do I need to do in order to give the mold better condition to grow?
  2. Can it be dangerous growing it?
  • 2
    $\begingroup$ What's your goal with this project? You don't really know what you've got in that tea-cup, and DIY dirty dish biology doesn't sound like a great idea in general... $\endgroup$
    – jakebeal
    Mar 14, 2021 at 18:39
  • 1
    $\begingroup$ What makes you think it's specifically P. digitatum? Penicillium molds are very widespread in the environment, and can be almost impossible to differentiate based on visual appearances alone. That being said, I echo @jakebeal - what is your ultimate purpose in this experiment? $\endgroup$
    – MattDMo
    Mar 14, 2021 at 19:17

1 Answer 1


You could place part of the mould into a cut in a piece of citrus fruit to continue its growth. Citrus can also host P. italicum, the below website is one mentioning how to differentiate between them.



Aspergillosis: (fungal spores growing in the lungs) which is uncommon.

Asthma: penicillium spores have been associated with increased chance of onset of asthma, and problems with breathing in people with asthma.

There may be other hazards.

I just cite one paper below, but a search using terms of penicillium and asthma shows lots more.

"Household airborne Penicillium associated with peak expiratory flow variability in asthmatic children"

published in :

Annals of allergy, asthma & immunology : official publication of the American College of Allergy, Asthma, & Immunology


Kemp W. Bundy, MD, MBA, Janneane F. Gent, PhD, [...], and Brian P. Leaderer, PhD

doi: 10.1016/S1081-1206(10)60139-1

  • $\begingroup$ thanks. It seems too dangerous to keep growing it. Should I worry that it was in my room for a few days? $\endgroup$
    – ziv
    Mar 15, 2021 at 9:26
  • $\begingroup$ @ziv as long as you're not immune compromised and you haven't been purposely inhaling the fungus, you should be fine. $\endgroup$
    – MattDMo
    Mar 15, 2021 at 17:08

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