Just to share this with you guys: whenever you find a rare seed the game let's you think you can not know which kind of seed it is until it is fully grown. Well, if you have World Adventures, this is no longer true. While having a camera in your sims inventory, click Shift+C to let the sim take a picture with it. Hover now over the planted seed when it just sprawled and you will see the name of the plant in green underneath your camera's canvas. If this hasn't added to the guide yet (at least, I wasn't able to find it) it may will add some nice hint for gardeners.