Common names that have been used to refer to the species include "crust-like cup", "pine-fire cushion",[4] "doughnut fungus",[5] and "pine firefungus".

[6] Fruit bodies (apothecia), which may be up to 6 cm (2.4 in) wide, are flat, with irregular lobes, and are attached to the growing surface on the entire lower side by numerous whitish to yellowish rhizomorphs.

[9] In very young fruit bodies, the surface is white; the brown color initially appears in the center and expands rapidly thereafter.

The spores of Rhizina undulata are fusiform (fuse-shaped), apiculate, minutely verricose at maturity, with one or two oil drops, and have dimensions of 30–40 by 8–11  μm.

The paraphyses are slightly club-shaped, tips encrusted with tubular setae, thin-walled, brown, aseptate and parallel-sided, tapering to a blunt point, and are 7–11 μm wide.

Discina ancilis bears a general resemblance to Rhizina undulata, but its fruit bodies lack rhizoids on their undersurface, and are attached to the substrate at a central point.

The presence of these fruiting structures, as well as their proximity to the trees, can be critical signs in diagnosis of Rhizina root disease.

He determined that the fungus can cause the death of four-year-old seedlings of several conifers, including European silver fir (Abies alba), eastern white pine (Pinus strobus), European larch (Larix decidua), Sitka spruce (Picea sitchensis), mountain hemlock (Tsuga mertensiana), Douglas fir Pseudotsuga menziesii, and sweet chestnut (Castanea vesca).

The roots of seedling attacked by R. undulata are matted together with a white mycelium that penetrates all parts of the cortical and bast tissues.

In the process of time the mycelium kills the tissues of the cortex and soft bast, whose elements become brown and completely dismembered ...

[17] Rhizina undulata attack in recently established conifer plantations in areas where slash burning after clearcutting has been performed is a well-known phenomenon.

One of the main ways to prevent the disease is to delay planting of trees for 1.5 to 2 years after a forest fire or burning due to the fact that heat is what activates the spores.