Orgot t1_jeb4i87 wrote on March 30, 2023 at 6:56 PM

Lots of plants from tropical climates have minimum temperature and humidity requirements. Gardeners and farmers in temperate or even polar climates cannot grow these plants outside at all, but greenhouses let them re-create those conditions indoors while still giving plants access to sunlight. Even plants that can survive outside often grow faster under the controlled conditions in a greenhouse. Pest management is also easier in the controlled environment. Some greenhouses can even have extra CO2 piped in for even faster growth.

northof420 t1_jec0848 wrote on March 30, 2023 at 10:21 PM

Seeing your piped CO2 comment. Could you technically put a brick of dry ice in a greenhouse and let it vaporize off or would that just be a negligible amount of CO2? Small greenhouse in my backyard (about 6’ each side I’d guess) not some massive industrial greenhouse

Orgot t1_jecwjyr wrote on March 31, 2023 at 2:20 AM

Good question! I don't know, but it should be possible to multiply the standard CO2 proportion of air by the density of air at your altitude by the volume of air in the greenhouse (216 cubic feet for a 6'x6'x6' greenhouse with nothing in it) to get the mass of CO2 inside at a given time. If you wanted to raise that by 10%, you'd just add that mass of dry ice - it has the same mass whether solid or gas.

But, air exchange with the outdoors will equalize that concentration gradient eventually, perhaps even as fast as the dry ice sublimates. Even in an airtight greenhouse, the enhanced CO2 levels will benefit some plant groups more than others, in a way that changes with day length and temperature. Timing probably matters too, with some plants shutting their stomata in the day.