Anamorph: conidiomata absent. Colony texture velutinous in agar culture, blue-grey to pale grey in natural habitat. Conidiophores long, appressed, with terverticillate branching, not aggregated into synnemata. Stipes 400-800 μm x 4-6 μm, robust, smooth-walled or with occasional verrucose ornament. First-order branches (rami) 15-25 x 4-5 µm, second-order branches (metulae) 10-15 x 3.5-4.5 μm, cylindrical, often inflated apically. Conidiogenous cells in large clusters 6.5-9 x 2.5-3 µm, ± cylindrical with a gradually tapering upper part, proliferating percurrently. Conidia 2.5-3.5 x 2.0-2.5 µm, ellipsoidal, finely roughened, dull green to grey-green [on CYA] with pale to yellowish or reddish brown droplets. Sclerotia absent. Teleomorph: not known.
Penicillium species need to be identified using defined cultural methods (or sequencing) and field collections can only be assigned to broad categories. P. brevicompactum is a name of convenience for many fungicolous Penicillium species, and it is probable that more than one species is involved.