  In HISQ simulations by the MILC and Fermilab Lattice collaborations, both the
light quarks and the charm quark are staggered. We extend staggered chiral
perturbation theory (\schpt) to include such all-staggered heavy-light mesons.
We assume that the heavy quark action is sufficiently improved that we may take
$a m_Q <<1$ (where $m_Q$ is the heavy quark mass), but also that
$m_Q>>\Lambda_{QCD}$ so that a continuum heavy quark expansion is appropriate.
Using this \schpt, the leptonic decay constant of the heavy-light meson is
calculated at next-to-leading-order. The pattern of taste splittings in the
heavy-light meson masses is also investigated.
