Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
pōpulnĕus, a, um, adj. [2. populus], of poplars, poplar-: frons, Cato, R. R. 5, 8; Col. 6, 3, 7: scobis, Col. 12, 43, 4; cf. populeus.