len gardener wrote:
g'day steve,

why till at all if you are going to do raised beds?

I wouldn't call yours raised beds, they're more like largish window
boxes, flower pots if you will, filled with what's essentially potting
mix.

Most folks who construct raised beds on top of real topsoil and fill
with real topsoil till twice a year; fall and spring. Soil compacts
and needs to be aerated and how else to amend nutrient depleted soil
but to blend in fresh composted organic matter. I know that there are
many lazy methods to revitaliz depleted soil, like spraying liquid
fertilizers or sprinkling fertilizer pellets, but that doesn't make
soil very much more productive than had nothing been done... perhaps
with potting mix that method is better than nothing. Anyway it's no
big deal to rototill a raised bed, with soil that's already been
broken up it shouldn't take more than ten minutes each.

corrugated roofing makes for good sides
http://www.lensgarden.com.au/

Nothing wrong with corrugated metal sides where you live but what you
built won't work where winters are severe, the ground will freeze,
heave that corrugated out of the ground and buckle that tin so much
that come spring it will need to be hauled to the dump. It's
important to realize that in gardening and construction what works
well in one climate probably won't work at all in another.