According to Boundless, a cloud-powered textbook and teaching resource, the main characteristic of imperfect fungi and lichen is an unclassifiable, or absent, sexual life cycle. For this reason, they are regarded as “imperfect.” Typically, imperfect lichen and fungi also live on land and have a mycelium, or mass of hyphae, that has a fuzzy mold-like appearance.
Imperfect fungi and lichen are in the phylum Deuteromycota; this means they do not have the sexual structures normally needed to classify fungi. According to the University of Hawaii, an asexual, or unclassifiable sexual stage, is one of the main reasons for classifying certain fungi and lichen as imperfect. Once the sexual stage is determined, the fungi is reclassified and placed into the appropriate subdivision.
Imperfect fungi are also polyphyletic, which indicates they have multiple ancestral sources. In other words, imperfect fungi and lichen are generally a mix of a number of fungi. This indicates that it is difficult to determine from which fungi they were originally derived because their genetic information has been recombined. Lastly, imperfect fungi and lichen produce asexual spores without the help of a sporangium. They produce conidiospores, or conidia, that are the unicellular spores that help the fungi reproduce.