We study coexistence interference that arises between multiple collocated radio interfaces on 802.11 based multi-radio platforms used for mesh networks. We show that such interference can be so severe that it prevents concurrent successful operation of collocated interfaces even when they use channels from widely different frequency bands. We propose the use of antenna polarization to mitigate such interference and experimentally study its benefit in both multi-band and single band configurations. In particular, we show that using differently polarized antennas on a multi-radio platform can be a helpful counteracting mechanism for alleviating receiver blocking and adjacent channel interference phenomena that underlie multiradio coexistence interference. We also validate observations about adjacent channel interference from previous studies via direct and microscopic observation of MAC behavior.