Quotes from the news wire:
The zinnia plant is very different from lettuce, it is more sensitive to environmental parameters and light characteristics. It has a longer growth duration between 60 and 80 days. Thus, it is a more difficult plant to grow, and allowing it to flower, along with the longer growth duration, makes it a good precursor to a tomato plant. The zinnia plant, though, showed signs of stress early on - possibly due to high humidity or water engulfing some of the plants.