Frost Blanket

via Valerie Jaquith:

I've grown vegetables at 9'000 feet in a very cold zone in Colorado high country for 15 years. Frost blankets are a must all summer to protect from hail storms, wind, unexpected frosts, BUGS,  etc. They make them in 3 weights, I use all of them at different times. I also have "hail cloth" for times of the year I don't use the blankets. But mostly I use the blankets, anyone in a cooler zone with risk of frosts really need to get some - cheaper than a green house and multi purpose.

Can be found from $7 to $21.