Greenhouse Heat
 

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.

Hi Chuckie,

I don't have your answer, but you might want to ask these folks.
http://forums2.gardenweb.com/forums/strucs/

Newt

I have also had a new problem. I cannot keep a warm temp in the
greenhouse. I would like to have a 70 degree day temp and 60 or 65
night temp. It is a small gh so there are no vents or windows. It is
just 7 by 5 ft. Is there any insulation tatics I can use to up the heat
without having a big electric bill?
Chuckie

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.

I have only been able to keep a 50 or 55 night temp no matter what I
do.
I live in norteastern ohio and for the last couple of days there really
has not been any sun to speak of. Today though the sun broke through
and the gh heated up to high temps. I had to open the door to keep the
heat down. I do not have any plants yet I am still waiting on them to
sprout but it there a temp the gh should be at when plants are growing?
Chuckie
NE Ohio

On 22 Mar 2005 15:25:37 -0800, "Chuckie" wrote:

I have only been able to keep a 50 or 55 night temp no matter what I
do.
I live in norteastern ohio and for the last couple of days there really
has not been any sun to speak of. Today though the sun broke through
and the gh heated up to high temps. I had to open the door to keep the
heat down. I do not have any plants yet I am still waiting on them to
sprout but it there a temp the gh should be at when plants are growing?

As I mentioned, many (most?) common veg and flower seeds need about
75F to germinate. This is why people often start seeds in trays on the
refrigerator or water heater -- bottom heat warms the planting medium
and the seeds sprout. Once they're up, they need light, and can take
somewhat lower air temperatures. There are various versions of heating
mats that will provide localized warmth. Take a look at

http://www.gardeners.com/Shopping/de...ecGro upNum=3

These can be quite pricey, but last a long time and use very little
power. People have also devised 'home-brew' heaters with electric
blankets and the like. Be careful -- electric blankets aren't designed
to be operated when wet!

If you have a seed-starting tray with a clear cover and bottom heat,
you have a mini-greenhouse that should protect the seeds even when the
big temperature inside the big greenhouse gets quite low. Once the
seeds sprout, and grow enough that you have to remove the cover on the
seed-starting tray, the bottom heat will still provide a fair amount
of localized warmth. It is suggested that things like tomatoes and
peppers not be set outside until the nighttime temperature is above
55F, so I would say that keeping the greenhouse somewhere above that
temperature for the growing plants would be sufficient.

Thank You I would actually consider heating pads but I can't afford
them right now. I have been sucessful keeping the house around 73
without any sun during the day. I planted these seeds 6 days ago when
will I begin to see green shoots?

On 23 Mar 2005 17:33:21 -0800, "Chuckie" wrote:

I planted these seeds 6 days ago when
will I begin to see green shoots?

Check the seed packets, if you have them, for *average* germination
times. You can also find info on the web by searching for "plant_name
germination" (without the quotes). Remember these times are averages,
not certainties. Do NOT dig up seeds to see how they're doing. :-)

"Frogleg" wrote in message
...
On 19 Mar 2005 16:23:26 -0800, "Chuckie" wrote:

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.

What do you recommend for the bottom heat? I have a home built greenhouse
with heat and cooling but it would be nice to just have to heat the bottom
until the plants get up.

On Fri, 25 Mar 2005 19:42:53 -0500, "Jack Allen"
wrote:


"Frogleg" wrote in message
.. .
On 19 Mar 2005 16:23:26 -0800, "Chuckie" wrote:

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.

What do you recommend for the bottom heat? I have a home built greenhouse
with heat and cooling but it would be nice to just have to heat the bottom
until the plants get up.

When I had money, I bought some sturdy heating mats specificially
designed fot the purpose. See

http://www.gardeners.com/Shopping/de...ecGro upNum=3

(The pricey mats with metal racks -- top row, 3rd pic from left --
were a little less then.) I also got a cheaper insulated wire that
one buried in the growing medium of a sort of open tray. Rather like
what must be insde an electric blanket, I think, but a reasonable
length and designed to work in damp/wet material. It was a little hard
to coil it around to give uniform coverage, but it worked.

I've heard of people using actual electric blankets. My concerns with
that would be electrical hazard and possibly range of the heat. It
doesn't take much to cook a plant in an enclosed space.

I have heard farmers and gardeners using manure under the greenhouse
to produce heat during the cold months. Apparantly, it works but you
have to regulate the heat with amount of rotting manure and available
sunshine. Electric heat would be costly if the greenhouse is large.

Yeah they are called Hot houses. Many of them were put right outside a
basement window. They would put about three inches of manure under it
and grow their plants during the winter.
Apparently it works from what I have heard.
Chuckie
zone 5