"p. cactorum" is a homothallic (only having one mating type, can mate with itself) oomycete, and displays the right angled mycelial branching with a constriction at the base of the branch, which is highly characteristic of other "Phytophthora" species. Within the hyphae, they have singular diploid nuclei that are regularly spaced. In addition, young hyphae only have cross walls separating reproductive parts; however older hyphae may have cross walls anywhere. Furthermore, although the hyphae are not the main survival unit of "P. cactorum", as long as they are not completely desiccated, they are capable of surviving until just above freezing temperatures.