Posted: 25/01/2014 at 10:34
Jimbo said that the greenhouse is too far away from the house to install an automatic system
Tomatoes are better kept on the dry side, especially in a greenhouse while he's away and not able to adjust ventilation flows etc.
I would grow the tomatoes in large pots - ours are a bit bigger than buckets, and leave a gap of 6" between the top of the compost and the rim - then we only water when the tomato foliage begins to droop but we absolutely fill the pot to the top. Then no more water until the foliage begins to droop again. Sometimes that will be a week later.
That regime produces tasty tomatoes, and helps guard against blight and blossom end rot.
Watering too frequently keeps the top of the compost damp resulting in making the atmosphere in a greenhouse damp and encouraging blight and other fungal problems