sfrose has written an explanation that makes it pretty simple to understand how to use Borg's breeding charts. The Magic X... ...or do you know how to play Tic-Tac-Toe, Bingo or Chess? Some people have been saying that they don't understand the Breeding charts. Let me see if I can explain it a bit better.
If you look at the Excel sheet that Borg has with his prices, you'll see that it is just a 23x23 grid table. 23 Flowers and 23 Foliage. Think of this instead as a very large Tic-Tac-Toe, Bingo or Chess board. The goal (as in the first two of those games is to fill in the rows, columns or diagonals.
The same is true for Plant Tycoon.
If you isolate the grid to make a 5x5 grid (anywhere, it doesn't have to be in a corner) something Magic happens!
Mark each of the corners with an 'A', then mark the cells half way between each of them with a 'B'. This is the plant that you will get if you cross one corner cell with another. i.e. cross a Spotted Astera with a Bluestar Maranta, and you will get a Daisy Fern (the center of the X.) The same is true if you go the other diagonal.
In addition, the rows and columns will do the same trick. A Spotted Astera and a Bluestar Astera will make a Daisy Astera.
Take this one step further and fill in the other cells, with a 'C' and that is the plant that you will get if you cross the 'A' and 'B' plants on either side (up, down or diagonal.)
Also, this works whether you have a 3x3, 5x5, 7x7, all the was to 23x23! The corners will make the plant in the center!
So what does this have to do with chess? There is a chess piece called the knight. It moves around the board by taking two steps in one direction and one in another. The Magic X works here also! It doesn't have to be squares that you isolate to find the Magic X. If you have a block of 7x3 cells, and you mark two corners on one side with 'A' and the corners on the other side with 'B', then if you make the center with a 'C' you'll get the plant that will be the cross between the opposite corners. You'll notice that you are taking two steps down and one over to find the center, and then again to find the other corner, just like a knight moves in Chess!
Again, this isn't limited to a 5x3 rectangle, any size will work the same, no matter where you are on the grid. 3x5, 5x3, 3x7, 5x9, 3x11, etc.
You may have noticed that my examples all used odd sized cells. What about a 4x4, or 6x8? Well it works the same for that, but it gets a little more complicated. There's no center cell of the square or rectangle to find the center of the Magic X. So instead, you find the cell that is one below or one to the left or both of the center spot of the X of the corners.
It's really quite easy once you get the hang of it.