"Dan L." wrote in message


Hmmm ...

Do plants need Oxygen as well as CO2?

The root growth for new plants I believe needs Oxygen more than CO2.
If one puts the propane barbecue heater inside the greenhouse this may
be bad for the plants because the heat would use up the Oxygen.

I don't believe any of these three points are necessarily true.

If I
went with a propane heater it would be a camper style heater in which
the heater is outside and blows the heat inside the greenhouse OR has an
exhaust vent to the outside. Electric mats under the plants are probably
the best way to go. Electric is also nice for the over head watering
systems.

Good to vent the Carbon Monoxide buildup if people work in the area and I
agree bottom heat is better.

Electric can be a problem if the greenhouse is not near a power source.

So therefore ... propane.

and for emergency situations a charcoal or wood grill would help.

Enjoy Life ... Dan

--
Garden in Zone 5 South East Michigan.