Why is it advisable to dry plants either in the oven or air-dried on screens above ground?

Question

and why never dry plants on concrete floors?

please help.... thanks

Answer 1

To sucessfully dry the plants, air needs to circulate around all surfaces, to dry evenly and quickly, so that fungus (mold) won't begin to grow. In the oven plants should be dried at the lowest possible temperature  so that the material won't get too dry and become brittle.