On Mon, 25 Apr 2011 14:39:41 -0700 (PDT), Chris wrote:
Would I be able to put a small cold frame there? I cannot have soil
there, so it would be used to harden off seedlings in Spring, not grow
anything.

Sure, that'll work. But the usual problem with cold frames is overheating, not
needing supplementary heat unless it's unusually cold and a very small frame.
I'd consider an automatic opener... makes life much easier unless you're home
all the time to adjust the coldframe. e.g.:
http://www.mastergardening.com/too-1...FQkSbAod01YzBQ

I'm a little more puzzled as to the "can't have soil there" problem. If
your deck can't take much static load, it's probably time to re-engineer it
so you don't wind up going through some morning when you step out with your
coffee and WHOOPS!!!!

But were I you, I'd probably toss a couple of bags of lightweight planting mix
in that cold frame in early fall and poke some holes in them to start winter
greens. Fresh homegrown lettuce in January tastes mighty good.