  We formulate the hydrodynamics of active columnar phases, with
two-dimensional translational order in the plane perpendicular to the columns
and no elastic restoring force for relative sliding of the columns, using the
general formalism of an active model H$^*$. Our predictions include:
two-dimensional odd elasticity coming from three-dimensional plasmon-like
oscillations of the columns in chiral polar phases with a frequency that is
independent of wavenumber and non-analytic; a buckling instability coming from
the generic force-dipole active stress analogous to the mechanical
Helfrich-Hurault instability in passive materials; the selection of helical
column undulations by apolar chiral activity.
