Overnight outside low 8 degrees F (-13 C).
Heirloom tomatoes growing inside new Earthship Education Facility.
Passive solar building, no back up heat.
A heirloom tomato (also called heritage tomato in the UK) is an heirloom plant, an open-pollinated (non-hybrid) cultivar of tomato. Heirloom tomatoes have become increasingly popular and more readily available in recent years.