3. Air
Although your tomatoes, and other indoor plants, will love the tropical steamy conditions created by your garden greenhouse, they will also benefit from a bit of air through an open window or door. Not only will this allow pollinating insects easier access than forcing their thoraxes through gaps in the construction, but it will also create a more stable growing environment and discourage nasty damp-related diseases from taking a grip. Furthermore, when temperatures reach scorching levels during the day, they usually plummet at night, and this exaggerated shift on the thermometer isn’t much fun for a plant.