You can put trees as well as crops inside (together if you want). They'll grow 40% faster than normal.
To build the Super Greenhouse, you need:
1. LOTS of space for this structure is B I G .
2. 20,000 coins
3. Materials: 25 Blue Pipes, 25 Glass Panes (both as free gifts from neighbors), and 4 Ventilation Windows (for 3 RC each).Hints:
You can put the Super Greenhouse on a Yard, but you will not be able to put crops in it, because you can't put crops on a Yard.
If you put only trees in the Super Greenhouse, it can hold 12 trees.
If you put only crops in the Super Greenhouse, it can hold 42 crops.
To further increase the growth speed, you can install Sprinklers inside the Super Greenhouse. Crops will be faster by 40% + 15% = 55%.