So, I have noticed that, while you can buy double plants (specifically, Hostas), you can't make/buy double width/length pots to put them in.
Currently, you can use two of the double plants (so, it looks like four plants, in total) to fill a huge, round container (i.e. the High Elf winged one).
Which looks great, assuming you have the room, which you don't always have.
Also, there is really only one style of pot you can do this with, which doesn't go with every style of house/furnishings.
Or, you can put one double Hosta in a large, but not huge, round pot and leave visible gaps on either side.
Yes, you can probably use a fern, or something, to disguise them; but, you may not want to do that and it is just one more furnishing slot taken up.
Would help if these pots came with earth in them (or an option of earth, or not - like some of the cups/glasses come with drink in them, or not).
Or, you can squeeze a double Hosta into a smaller, round pot and make it look cramped and (depending on the pot) risk having stray stalks left outside the pot.
However, what you can't currently do, is find a double sized, longer/wider trough/lozenge shaped pot/container to put a double Hosta in.
On a side note, you also can't buy a single (pink) Verdant Hosta; only doubles.
The single ones exist in game, but not for furnishers.
Would be nice if you could buy them in singles and also, ideally, in triples (with triple width/length pots/containers also available).