Several studies have been done at Wagner Research in this area. The largest study involved analyzing the distributions of many thousands of plant internodal spacings (spacings between leaves, stems, and branches, for example) around an electric power substation. We measured both the electric and magnetic fields for different samplings of spacings. For plants growing in the electric fields, near the Grants Pass, Oregon substation, the average internodal spacing became larger than for plants growing farther away.

60 Hz and its harmonic's fields seem to eliminate many shorter internodal spacings. Shorter internodal spacings became scarcer as plants came closer to substation. Our first hypothesis was that as the internodal spacing frequencies characteristic of the plant combined with the substation frequencies, the ones closer to matching were cancelled in some way. The missing spacings reappeared in plants further away from the substation.

Thus it appears that the affects of electromagnetic fields on growing plants are much more subtle than thought heretofore. The data all confirm the wave nature of plants. Plants don't seem to be harmed by electromagnetic waves, if the fields aren't too large, but their growth structure is often changed. See Waves in Dark Matter pp. 129-143 for data.