I read that they need protection under 14 degrees farenheit. Is there a maximum temp to worry about? And whats the best insulating material?
What kind if maples are we talking about? And how are they being grown - in the ground or in a container?
IME, any maple planted in the ground can tolerate 14F or lower for at least a few days. Most JM's are listed as hardy to at least zone 6, so that means they can tolerate down to 0F. Planted in a container is a bit different. Trees planted in a container lack the insulating factor of all that soil mass around them. The top growth can withstand some very cold temps - like the 0F - but the roots are much more cold sensitive. Root damage can occur at around 25F, so if you have JM's in a container and you anticipate temps in the low 20's for any length of time, then protection is well-advised. You can bring them into a garage or shed or place under a deck. Wrapping the pot with bubble wrap can help, as can stringing xmas lites around the pot.
You do not want to keep the containerized tree very warm, either....no more than about 45F (so bringing indoors not advised).
I have about 15 1-2 year maples in terra cotta pots. My unheated garage has some broken windows. I'm sure this is a common issue.
How much bubble wrap would it take? How about putting them in boxes, and mulching all around the base of the container? Or perhaps heaping soil all around the planters?
I really would hate to lose 15 brand new maples that I just bought.