Sue, Here in South Florida we grow out in the wide open spaces. We can have many days of1" rains and have high humidity most days. So our growing media must survive this. We would have trouble with your bark/peat mix because the decomposition would be rapid and start blocking air movement in 3 to 4 months. If we grow under cover and hand water( too much work) the mix can last much longer. So we aiways are looking for material that will last longer but still keep ouir babies happy. Tim Anderson Palm Hammock Orchid Estate Miami Fl.