One thing that will really help you is to understand how to pollinate plants. You need to make sure which plant you are getting pollen from, and which one you are pollinating. To make more of one kind of plant, click on it to select it after it matures and has pollen. Then drag the pollen from the pollen area onto the same plant. Then it will make more seeds for that specific plant.

To cross-pollinate, click on a plant to select it after it matures and has pollen. Then drag the pollen from the pollen area onto a different plant. That will cross-pollinate those two plants and usually produce a different species (foliage, flower, or both).

Keep in mind that once you drag pollen to a plant, the selected plant changes. That's probably what's happening to cause you to get plants that you don't expect.

If you want to see picture of all the seeds, look at the PDF document in this post in the Plant Tycoon Guide.