Colony characters can be distinctive and characteristic of a species. However, colony appearance is difficult to describe with sufficient precision for it to be very useful for identification. Growth rates in culture can be useful to distinguish otherwise similar species. The production of conidia from effused conidiophores, or from conidiophores aggregated into fascicles or pustules is usually characterisitic of a species. Diffusable pigments can also be characteristic, although the colour of such pigments does not vary a great deal in Trichoderma. Strains referable to section Longibrachiatum typically have conspicuous bright greenish-yellow pigments, at least when first isolated. Dull yellowish pigments are common in many species, but are not very distinctive. Some species are best characterized by a complete lack of pigment in reverse, whereas reddish pigments occur in reverse in a few isolates. Characteristic crystals produced in the media have been reported only for Trichoderma aureoviride. Indistinct mouldy or musty odours are commonly produced by different strains of Trichoderma. Characteristic aromatic odours resembling coconut are produced commonly by strains of Trichoderma viride, and sometimes also by Trichoderma atroviride.