"Steve" wrote in message
...
We're a bit short of space in our garden, but there's a nice flat
roof... It's the normal black type thing. It's south facing, with a
wall behind it so it's a real sun trap.

Years ago my brother had a garden on the roof of his flat complex in
London......in addition to growing grapes in pots plus flowers etc. he built
a small greenhouse for growing tomatoes and the likes........not a big one
but big enough to grow 1/2 dozen tomato plants.....excellent
results......had a hosepipe connected up to the roof for easy
watering.........he could grow pretty much much anything he
wanted.........HW