The physiological, morphological, and biochemical characteristics of seedlings of common amaranth (Amaranthus retroflexus L.), blue licorice (Agastache rugosa (Fisch. & C.A. Mey.)), and field pennycress (Thlaspi arvense L.) after a 6-h exposure of their germinating seeds to a permanent magnetic field with induction of 50, 80, 100, and 120 μT were studied. The conducted studies showed that the studied range of magnetic field intensities does not affect the shoot and rootlet length of seedlings in comparison with the control values. Wave-like changes in biochemical parameters (concentrations of flavonoids, malonic dialdehyde, sums of low-molecular weight antioxidants, sums of saturated and unsaturated fatty acids, activity of peroxidase and superoxide dismutase enzymes) in the seedlings of the three plants studied after 6-h treatment of their seeds with a permanent magnetic field was shown.