That is all you can upgrade. The only other things you can do are start new gardens. You can have up to 8 gardens. If you hit Seedos and he throws seeds in your garden, in the next garden he will like you again. You share money with each garden you have. So spend it wisely! The only thing is that every time you have to wack all the hard soil and it takes a long time if you have all the garden space you can get.