I had saved seeds from last years Morning Glories, so I planted some more in smaller pots 2 months ago. Now those are blooming in the little 3" pots!
Another idea for a free house plant is to plant a few lemon seeds, from a store-bought lemon, and watch a tiny lemon tree sprout up.
The lemon trees are in the pink pot, in the middle. One of the Morning Glory vines is to the left of the pink pot.
The clay pot, just behind the pink pot is a couple potatoes that we planted a few eyes. They will all be planted outside as soon as it warms up, but for now they liven up the house. I'll bring the little lemon trees back inside next fall.