Hi everyone, I'm in the super early stages of thinking through how to go about growing a durian in-ground in Zone 6 in a greenhouse. The greenhouse is not yet built, but I'll have the ability to design it according to specifications. Of course, it would be nice to save on utilities and costs, but survival and fruiting of the tree is most crucial. (Yes, I realize this is no easy task).
Air temperature aside (which I think is a lot easier to manage using traditionally available heating), there is the issue of soil temperature. Because the greenhouse floor will be about 4ft in the ground, the natural temperature will hover closer to 50, obviously hotter in the summer and changing with day/night. I know that I'll need to keep the air temperature around the plant from dropping too much lower than 70, but does anyone know what ground temp for the Durian root system should be? As I understand from some research, the systems tend to be pretty shallow, especially if I am pruning the tree to stay shorter than 15 ft.
And, from a design perspective, what is the best way to install a permanent heating solution that can take "abuse" from growing roots without damage? Obviously, this has to be a solution that can last a very long time, given the fruiting habits of durians. I've looked at water-based systems which seem susceptible to a stray root pushing on it the wrong way, as well as normal electric heating elements, and I just don't think they'll last long enough, and replacing them as the tree grows would be problematic. I've considered pumping hot greenhouse air into the ground with piping like a heatsink, but don't know how consistent that temperature is and whether it would last through cold winters.
Thanks for your thoughts... I'm committed to making this work and will gladly share the process of construction when the time comes.