I made these little "pot plants' after seeing some on a website. The first I made was the African Violet. I found that the pot was rather floppy, despite having a round of cardboard in the bottom, and being stuffed tightly.
When I made the first cactus, the tall one, I used a cardboard circle from the centre of a ball of crochet cotton with a circle of card taped on the bottom.
For the others, I used a centre card cone from a cone of knitting yarn. I cut the cone into three, and taped a circle of card on the bottom. I then covered it in crochet.
I think they look rather cute, and of course, no water is required!