I am working on a green roof in St. Louis, MO which is due to be complete by October. We are having difficulty getting plant cuttings from local nursuries, as the planting window is so short for the fall (Sept 1 - 15). Thus, we are looking to install the plants in the Spring instead, but I can't find any mention of timing of install in the Reference Guide. If we do this, are we breaking some rule about when the green on the greenroof is actually installed?