  We introduce the density matrix renormalization group (DMRG) method as an
efficient computational tool for one-exciton approximations with off-diagonal
disorder. This method allows us to reduce the computational effort by
targetting only a few low-lying eigenstates at each statistical sampling, in
contrast to the exact diagonalization methods that compute the whole spectrum.
As an application of the method, we study excitons in two families of branched
molecules called dendrimers using a recently introduced simple model. We
compute the absortion peaks for these dendrimers varying their generation
number $g$ and number of wedges $w$.
