Spores olive brown in print, melleous, elliptic-subfusiform, apiculate, suprahilar depression or applanation present, 9-13 x 3.8-4.5 µm, smooth. Hymenium composed of basidia and cystidia; basidia hyaline, clavate, 33-45 x 8-10 µm, 4-spored: cystidia scattered, hyaline, thin-walled, ventricose-rostrate, 50-75 x 9.5-16.5 µm, projecting to 30 µm beyond basidia. Hymenophoral trama bilateral, of the Phylloporus subtype, hyphae of lateral stratum only slightly divergent; clamp connections absent. Context of pileus pallid yellow, unchanging. Taste mild. Chemical characters: KOH on pileus- darkening with reddish brown tints; on context-salmon pink: NH₄OH on pileus darkening with red, flush; on context-n.r.

Singer (1962) recognised four species of Phylloporus, of which only P. rhodoxanthus (Schw.) Bres. was considered completely known. The remainder were known from dried specimens only. Phylloporus rhodoxanthus was regarded by Singer (1945) as a more or less cosmopolitan species composed of four subspecies. The combination of the unchanging context, slow bluing of damaged lamellae, and the absence of a bright blue colour reaction with ammonia distinguish P. novae-zelandiae from all subspecies of P. rhodoxanthus. A positive colour reaction with ammonia was considered of generic significance by Singer (1945) but on the present information, it appears to be restricted to P. rhodoxanthus. Despite the fact that Phylloporus is a lamellate genus, the limits between the Boletaceae and strictly lamellate families of Agaricales are clearly defined since the blue discolouration of the damaged hymenophore or context does not occur in closely related families such as the Paxillaceae.

No species have previously been described from New Zealand although both Heim (1950) and Horak (1970) reported that Phylloporus was represented in the fungal flora of the country. An Australian species P. hyperion (Cooke & Mass.) Singer, was recorded from New Zealand by Massee (1898) but Singer (1955) showed that the collection on which this record was based was a species of Gymnopilus (Cortinariaceae).