Growth and interactions of Piptoporus quercinus were studied in artificial culture to give insights into the ecological characteristics of a species which is both rare and widespread. P. quercinus grew slowly under all conditions, the maximum ranging between 1.9 and 3.15 mm d−1, depending on isolate, at 25 °C pH 3.75. Upper limits for growth were 25–30 ° or above 30 °, depending on isolate, and pH 6.6. Lower limits for growth were 5–10 °, between −1.75 and −2.5 MPa; there was still growth at pH 1.81. Preincubating plates at 5 ° for 77 d and then incubating at 20 ° resulted in a significantly greater extension rate (2.89 mm d−1) than when incubated continuously at 20 ° (1.70 mm d−1) for one isolate though not for another isolate. P. quercinus survived exposure to low temperature (−18 ° for 7 d), showing renewed growth, albeit limited, after a lag of 37 d. It was a poor combatant, being unable to replace any of the eight fungi (with a range of ecological roles) against which it was paired, and being replaced or partially replaced by most, on 2% MA at pH 5.49, at pH 3.75 and at −1.25 MPa. It did, however, inhibit extension rate of some other heart rot fungi. Results are discussed in an ecological context.