In a previous post or two on microclimates, I've mentioned that I grow zone 10 plants in my zone 8b yard.
One tree that has a deep allure for gardeners is the Key Lime. This tree has almost an almost shamanistic pull upon anyone from about Broward County down south to the Keys. It represents the tropics. Margaritas. Salt breezes.
And of course - the king of all citrus confections - Key Lime pie.
Basically, Key Limes =
The problem is: Key Limes can't stand freezing since they're one of the most tropical of all citrus. Up here, the poor trees will freeze to the ground ever year, then limp back with a foot or two of growth, only to get knocked down again. Growing them without protection is impossible - and growing them with protection is risky and time consuming. Can you really be at your house for every frost? Will you remember to wrap your viciously thorny Key Lime tree with Christmas lights and cover it with blankets? Will you watch the weather like a hawk all winter?
Like I said - it's time consuming... and I really don't want to bother.
Fortunately, I've found a way that works without all that trouble. I grow my Key Lime tree outside and unprotected and it's doing great.
Here it is this very February, after we've had close to ten freezes:
Cool, huh? The tree is completely and utterly unscathed, thanks to a tree-training method called "espaliering" and the almost mythically powerful south wall of my house.
To do it, I nailed those three pieces of galvanized conduit into the ground with a hammer and also secured them to the wall near their tops. The tree is planted within a foot of the wall, keeping it safely inside the warm pocket created by the concrete's thermal mass. As branches grow forwards, I tie them back to the conduit, keeping them from reaching out too far and into the Frost Zone of Death.
You know... I think I might need to set a few conch shells down to match the coconuts (sadly, imported from south Florida) at the base of that tree.