Mini-game -- the type of plant that eventually grows depends on several things - the type of pot used, the type of dirt used, and the type of water used (or water combination). For example, to grow a mushroom, you would have to use a wooden flower pot, use peat moss, and water your seeds with foul water. From the time you plant the seeds until harvest time should take about 2-3 weeks. Each flower pot should be able to grow a dozen plants. Obviously, there would need to be a cap or limit on the number of flower pots you could have in your home. As with any plant, it should not be over watered or under-watered (water no more than 1x per day, water no less than 3x per week).

Details -- Flower pots can be made from 3 or 4 different types of materials (earthen, wood, ceramic) and are crafted. Flower pot recipes would have a chance to be found just like any recipe (looted from containers and dropped from mobs). The best flower pots could be sold by Rolis Hlaalu for writ vouchers. Next, you need to put dirt in your flower pots -- and there should be a few different types of dirt available (sandy, peat moss, clay). You gather the dirt via a random drop from animals/trash mobs. Next you need to have some seeds to plant ... all flowers/mushrooms have a chance to drop 'generic seeds.' Lastly, your plants need to be watered -- bottles of water can either be obtained while fishing (from wet gunny sacks) or from Rolis Hlaalu for a few writ vouchers. There should be 4 types of water -ocean, lake, river, foul.

The mini game consists of the community doing a lot of 'trial and error' and pooling information while everyone tries to figure out what 'combination' of a.) flower pot type, b.) dirt type, and c.) water type (or water combination) will produce a particular type of flower/mushroom to grow.

I don't think it's necessary for every single type of flower/mushroom to grow this way, but definitely the more popular flowers and the more rare mushrooms.