In the raised bed threads, some people indicated they extended their
growing season by a couple of weeks at either end. We bought a house
with an unheated green house last year and I kept track of the
temperature. Generally speaking the lows in the green house were the
same (-5 to -10 C) as the outside temperature. I did have water in
the green house (~40 litres) to act as a heat sink.
The transition from winter to spring here is abrupt and variable.
Days warm up to 15 C but the overnight lows are well below freezing.
Do the people who have success extending the season live in milder
climates with more gradual springs?
Are there better techniques than using water as heat sink?
My tomato plant is still producing and budding in Tulsa Oklahoma area.
All I did was put up a frame around it and wrap the frame with clear
Then I put a 100 watt bulb on a well house thermostat so that it comes
on at 40 F, and a florescent grow light on a timer to keep my days at
We have had a few freezing nights already, and everything else is
pretty much dead, but the tomatoes are still producing and even
Something you may want to try is;
Use an old hot water tank hooked to a wood stove so that you can
cheaply heat up the room and the heat sink water when it is colder.
Make sure that the green house is closed up tight, with a good door
Use 100 watt bulbs on well house thermostats in clamp on brackets to
set around next to the plants to help keep them warm.
Divide up the green house by making little green houses around the
plants and use the bulb inside that.
Make your heat sink out of full 55 gallon drums. Bigger holds the heat
longer then smaller.
I found there was a period of some weeks (2-5, depending on the
season) where unheated hoop house protected plants into the fall, and
gave me at least 4 weeks jump in the spring.
If you have an actual greenhouse, ie, glass/plexi, I suspect there
might be a leak somewhere. I routinely had air temps in the 40s in
the dead of winter (z5) when the sun was out, and I KNOW my doors were
not airlocked/air tight.
This is NOT to imply you should be able to grow warm season crops with
no heat a-toll.. But cool weather crops should be no problem for you.
If you go that route, you want to make sure you do not overheat the
GH.. keep the highs around 39-40 max.
According to my "real property report" I have a portable shed/
greenhouse. That said, one side is glassed in with sliding storms on
each end. The green house and attached shed are normal garage style
construction and on a cinder block foundation wall. The green house
has slatted (2*4) floor over dirt. I can heat it, two infra-red heat
lamps (I really don't want to know how much it would cost to use
these) and an oil filled heater I bought for the house. There is a
fan that blows through a 3 in hole, I don't think it has a heating
I don't want to heat it because then it would be cheaper to buy the
plants I need/want: 6 tomatoes, 24- 48 bedding plants, 20-30
geraniums. Not that I ever pay full retail :)
We just bought the house last year and I'm learning to use what I
have. Also, I have a cold frame (strawberry patch) and a supply of
Thank you all for your replies.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.