Aspergillus flavus has the capacity to grow on many nutrient sources. It is mainly a saprophyte and grows on dead plant and animal tissue in the soil, which is important for the recycling of nutrients. Because it grows well on decaying vegetation, one common place you might find Aspergillus is in compost or on fallen leaves. However, this fungus is also a parasite and can use living organisms as hosts. Host species include corn, peanuts, nut trees, cotton, and even humans.
Typically this organism favors hot, dry conditions which makes it unique in comparison to other fungi. The best temperature for growth is 37°C (98.6°F). However, it can grow at any temperature between 12-48°C (54-118°F). Aspergillus flavus is omnipresent in nature but has a more limited growth indoors. Aspergillus molds thrive best in oxygen-rich environments and also on materials that are rich in carbon which they feed off of for nutrients.
Aspergillus oryzaecan often be found growing inside dirty air conditioners inside of buildings or in your own home. This has even been known to be a problem in some hospitals. Aspergillus may also grow on or inside walls in homes, especially if the house is damp or has been damaged by flooding.