[en] We study high-order harmonic generation (HHG) from aligned molecules ${\mathrm{H}}_2^{+}$ by varying the laser wavelength from 400 to 2300 nm. Our simulations show that the wavelength dependence of the integrated HHG yield is influenced significantly by the molecular orientation. Our analyses reveal that the electronic dynamics and the interference effect relating to the molecular structure and orientation play a dominating role in the wavelength-orientation-dependent HHG yield. The wavelength scaling of the HHG yield associated with long and short electron trajectories is also addressed. We find the contribution of short trajectory scales vary differently for short and long laser wavelengths, which provides important suggestions for the experimental study of the HHG scaling law. (paper)