The Argenmesh and Soft&Safe fabrics have the lowest resistivity and are therefore the most conductive. Both use silver threads so you don't have to worry about any copper absorption.
By the way, I saw indoor experiments where two cut flowers were put in separate water vases and a grounding wire was inserted in the water of one and not the other. The flower which was grounded stayed fresh much longer. the same experiment was done with tulip bulbs, and the grounded bulb grew much larger and faster.