The morphology of needle shaped crystals is, usually, ill-predicted when using the common attachment energy approach. Here we explain the needle shape of triacylglycerol crystals on the basis of a two-dimensional nucleation growth mechanism. For that the edge energies of 2D nuclei on the surfaces of the various crystal faces is determined and turns out to be much lower than expected when applying the attachment energy criteria. The edge energies are found by determining the connected nets of the various faces that follow from the crystal structure and the interaction energies between the molecules. The results are confirmed by Monte Carlo simulations.