  Edge reconstruction modifies the electronic properties of finite graphene
samples. We formulate a low-energy theory of the reconstructed zigzag edge by
deriving the modified boundary condition to the Dirac equation. If the unit
cell size of the reconstructed edge is not a multiple of three with respect to
the zigzag unit cell, valleys remain uncoupled and the edge reconstruction is
accounted for by a single angular parameter $\vartheta$. Dispersive edge states
exist generically, unless $|\vartheta| = \pi/2$. We compute $\vartheta$ from a
microscopic model for the "reczag" reconstruction (conversion of two hexagons
into a pentagon-heptagon pair) and show that it can be measured via the local
density of states. In a magnetic field there appear three distinct edge modes
in the lowest Landau level, two of which are counterpropagating.
