On 19 Mar 2005 16:23:26 -0800, "Chuckie" wrote:

I have just started some plants in my greenhouse and would like to know
what heat temp I should keep it at. It is a small gh and I am very new
at it. I am growing mostly vegtables and perenials.

Does "started some plants" mean planting seeds? In that case, you need
some localized bottom heat to keep the germination medium around 75F.
The entire greenhouse doesn't need to be maintained at 75F to start
the seeds.

For the rest, (reading your follow-up post), the very design of
greenhouses makes rapid heat transfer one of the facts of life, though
some (clear) materials may retard it more than others. On a sunny day,
the interior can easily be 20-30 degrees warmer than the outdoors.
However, this heat dissipates quiickly when the sun goes down, and
will soon reach something very close to the outdoor temperature.

You have 2 problems: with no vents, the inside heat will build up
enough to cook plants once it's above 60F or so outdoors. And with no
additional heat source at night, if it is below freezing, they will
freeze.

I don't know of many common veg or perennials that require nightime
temperatures of 65 degrees. You might more reasonably shoot for 55F.
There are ways other than electricity to heat greenhouses -- search on
"greenhouse heaters". But you *will* have to supply supplemental heat
of some sort. Unless you live in zone 9+ -- you didn't mention your
local conditions.