Posted: 08/04/2014 at 11:16
Tomato's need minimum 10C and maximum 20-30C, depends on where you are really, here on the North East Coast one foot in the sea it is still a bit early unless you have heat in the green house or as I have a sand box with heating.
Place young plants which should be in 4inch pots in a warm area of the green house at floor level, often ten degrees warmer than higher up, cover with fleece at night and take that off in the morning, "I know hard work" a minute or two in the greenhouse before going to work and after sooths and brings you down from the tensions of work.
In my case a sand box with warming cables and thermostat means you do not have to waste heat on the whole greenhouse and shelves above the sand box means you can lift the plants above the heat whilst starting more in the sand, I surround it with bubble wrap to keep the heat in.
Once the plants are in the 12 inch pots on the floor a minimum heat frost guard keeps them happy, heating is costly and wasteful so use fleece or bubble wrap to contain the heat that builds up during the day. Ventilation is also very important.