How to get brown seeds?

To get brown seeds takes a lot of work, you'll need to first of all make the Flower Pot, then when it has been merged to a level that it can start to give items, you need to get the empty seed packets.

Flower Pot

Keep merging those until you get the full seed bag, and then it will start to give you the brown seeds that you need to grow into a Flower.

Flowers from the Brown Seeds