The soil is the key to being able to breed the Magic Plants. You can successfully grow
only the common seeds until you have better soil. If you try to cross pollinate plants before you have better soil, the plants from those seeds may not survive. The best thing is to be patient and self-pollinate common plants until you have enough money to buy the best soil. After that, you can safely cross pollinate any plant and will start making lots of money and discovering Magic Plants.
