Gardening and Cacti

I have been growing cactuses for many many years, but never had a regular big greenhouse. What is pity because living in quite high latitude (48 grades) the effective and usable growth period for cacti is quite short. No more than 4 months in outdoor conditions. Peoples who have greenhouses, ideally with heating, can extend this time by two good months at least. So I opted for this compromise: A polycarbonate 1x1 m sized mini greenhouse for about 90 EURO. Photo taken in the morning when still in shadow, and still closed :) Greenhouse of this size can easily cook your plants if closed in direct sunlight for 10 hours and I am not there to "babysit" it so some king of automatic opening is a must. And not too expensive of course. So here come thermal based automatic window openers. To make the long story short: there are two types of openers - as available on Amazon. Wrong one First I got this one - and it cannot be fitted in small greenhouse anyhow, so I was left without automat...