I grow figs in-ground in Maryland. I have found aluminum bubble
insulation to make an excellent covering if run all the way to the
ground -- it lets the ground warmth come up and keep the plants 10-15
degrees warmer during cold spells. The insulation also reflects off
the sun so on hot days it does not get too hot under the covering.
Here is a picture of my figs covered:
They have taken -2F and come through with almost no damage. I use a
normal stapler to build the cover from a roll of aluminum bubble
insulation. I use ground staples to attach the cover to the ground,
and a rope cinch around the waist to help the cover stay in place in
high winds.
This covering ends up costing a bit more than other kinds of wrapping
but I feel it is a safer and more reliable covering method. I don't
pack any insulation under the cover, but people in colder zones could
probably get even more insulation value by putting leaves etc under it.