Seed updated after May 2019.
This is a seed, which can remain in inventory indefinitely. Even the growing plant can be safely put in inventory; doing so only pauses it. The seed is transferable, but the growing plant is not. To birth, make sure the land you're on has at least 9 prims free, rez seed, touch it, and select "Grow" in the menu. (NEVER "Open", "Edit", or otherwise attempt to unpack a seed in any other way.) After you receive the actual potted plant, you can dispose of the empty seed.
The PlantPets website has most of the things you might want to know about PlantPets under "User Guide" and "FAQ": http://plantpets.dejapi.com/?q=userguide
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PlantPets is a team project for creating intelligent growing flowers and plants in SL. We offer more than 300 plantpets including roses, orchids, hibisci, and many others. All plants are low-prim as the prim-flowers are temporary rezzed above their pots. Plantpets are breedable and breeding them can be free of charge. Each plantpet can give one baby seeds every 52 days if kept at least 50% happy and 50% healthy. However, if either their happiness or their health is below 50% then they stop counting down the days to baby until both their happiness and their health become again at least 50%.
Taking care for plantpets is also free. They need only water to be happy and healthy and they are watered simply by pressing a menu button. If left dry for long period of time they can die but then they can be reset free of charge and grow again. When taken to inventory a plantpet gets paused, i.e. its parameters do not change.
Plantpets grow according to the menu-specified speed. In any case, the growth of a plant is slow and normally you should allow at least a couple of minutes before you see visible change. The speed of growth does not affect the time a plantpet needs to produce a baby seed.
All plantpet seeds are transferable and we encourage breeders to sell plantpet seeds at any price they desire. When an avatar grows a seed they receive the actual plantpet which is not transferable.