Most vertical farms currently concentrate on low-biomass crops – things like herbs, salads and small fruits and vegetables which weigh less per portion – because there is a greater yield for the amount of heat, light and water that needs to be supplied. They also have short life cycles, so make maximum use of space, says Vickers. A leafy green will grow quickly and be ready to harvest in days or weeks, whereas a pumpkin would take months to grow and needs to cure in sunlight.