The green roof test panel shown here is one year old. We are preparing the unit for hurricane wind tunnel testing. The only irrigation the roof panel has had is rainfall, and survived a very dry winter and spring. Green roofs present a different growing environment for plants than do the ground. No matter how rocky or little soil there may be, the ground offers a consistently cooler place for roots to exist. A three inch thick extensive roof soil layer can reach temperatures of 140 degrees F or higher while the ground temperature is significantly lower. So for plants to survive on a non-irrigated green roof, they must be carefully chosen.
We are raising a new breed of plants in the greenhouse where they are exposed to growing conditions much like those to be experienced on a roof. Heat and prolonged drought. With trials well into a year now, the plants go through prolonged leaf impact, however when finally brought out and exposed to rain, the bloom and grow. Importantly, we look at the potentially for flammability when using plants with dried leaf matter or leaf litter.
One interesting quality we are seeing more and more of is the ability for plants to absorb humidity here in Florida. Fortunately, even when the temperatures are torrid, the air relatively humidity may be quite high. Air humidity can make the difference between a plant dying and a plant surviving a long period of non-rainfall.
Finally, with water shortages here in Florida and watering restrictions in place by municipalities and water management districts, why would a green roof designer recommend irrigation? It is because they do not understand the 'right plant, right place' concept. We have been working on green roofs for many years and understand those plants that work and those that do not.
Call us to discuss your next green-roof project! Kevin 904-294-2656