Way to get a PlantSim:
1. Buy the science object from university.
2. Study science until you reach level 9.
3. Obtain a seed (any type of seed, probably best to find more than one just in case something goes awry). Gene splice the seed until it turns into a Forbidden Fruit seed.
4. Analyze the Forbidden Fruit seed. There will be a sample of the seed in your inventory. Clone this sample. It'll turn into a fruit.
5. Eat it.
Four hours later you're a PlantSim.
To have a baby, either have two PlantSims of the opposite gender have woohoo, which results in a Forbidden Fruit seed being put inside the female's inventory, and planting it (level 7 or above), and waiting four days (don't forget to water and tend garden). When the option to harvest appears, click THAT (DO NOT tend garden at this point). A PlantSim baby will most likely be pulled from the dirt.
To have a single PlantSim grow a PlantSim baby, just do the gene splicing experiment and plant the Forbidden Fruit when you get one.
IMPORTANT NOTE: Who ever harvests the PlantSim will be its parent in-game, so make sure who you want the parent to be is the one who harvests it.