  We study the dynamics of an electron spin in a graphene quantum dot, which is
interacting with a bath of less than ten nuclear spins via the anisotropic
hyperfine interaction. Due to substantial progress in the fabrication of
graphene quantum dots, the consideration of such a small number of nuclear
spins is experimentally relevant. This choice allows us to use exact
diagonalization to calculate the longtime average of the electron spin as well
as its decoherence time. We investigate the dependence of spin observables on
the initial states of nuclear spins and on the position of nuclear spins in the
quantum dot. Moreover, we analyze the effects of the anisotropy of the
hyperfine interaction for different orientations of the spin quantization axis
with respect to the graphene plane. Interestingly, we then predict remarkable
long decoherence times of more than 10ms in the limit of few nuclear spins.
