quality of being phytotoxic.
phytotoxicity (Wikipedia)
Phytotoxicity describes any adverse effects on plant growth, physiology, or metabolism caused by a chemical substance, such as high levels of fertilizers, herbicides, heavy metals, or nanoparticles. General phytotoxic effects include altered plant metabolism, growth inhibition, or plant death. Changes to plant metabolism and growth are the result of disrupted physiological functioning, including inhibition of photosynthesis, water and nutrient uptake, cell division, or seed germination.