In this study we investigate growth morphologies and epitaxial relations of small molecule organic semiconductor crystallites on the surface of graphene (Gr) and hexagonal boron nitride (hBN). The molecules under consideration in our study are the rod-like oligophenylene para-hexaphenyl (6P) and dihydrotetraaza-heptacene (DHTA7) – Fig. 1a. 6P is a model molecule for understanding growth and interfacial phenomena in organic electronics, which is known to form needle-like crystallites (with flat lying molecules) on the surfaces of both Gr and hBN [1,2]. As a contrast to 6P, DHTA7 is not expected to form a herringbone structure due to dipolar interactions and hydrogen bonding between neighboring molecules. Nonetheless, needle-like crystallites of DHTA7 – in some cases over 500 µm long – have been observed both on Gr, and on hBN. By atomic force microscopy (AFM) analysis (Fig. 1b) of the preferred growth directions (Fig1 b-c) and knowing the preferred adsorption sites of individual molecules obtained from density functional theory calculations, contact planes could be revealed (Fig1 d), as (6 ̅29) 6P plane in the case of 6P/hBN interface [2], or (111 ̅) for 6P/Gr [1].