Answer: When three plants have been grown together in one container it can be quite difficult to separate them without damaging one or more of the plants. To some extent it will depend on the type of root system they have as to how well they will respond to being separated.
Sometimes it is easier to simply keep them together as a group. Often enough, eventually one of them will become dominant and the other two may dwindle away, or sometimes the overall combination will begin to look like one single bigger plant. If your real desire is to have more plants instead of just one, you may be able to propagate it by tip cuttings for example instead of taking this one apart.
Assuming you really want to separate these, spring is usually the time to do it. The best way is to water them well the day before, then take the root ball out of the pot and examine it. Try to trace some of the most important roots from each plant so you can preserve them. Then just do the best you can and separate them.
Sometimes you have to use a knife, sometimes you can gently wriggle them apart with your fingers, this really depends on what kind of plant it is. A certain amount of root loss is usually inevitable.
Next, you would repot into individual pots using soil mix as closely matched to the original as possible. Make sure the plants are not put into pots that are too big for them, as this can cause you to overwater.
Last, water carefully to keep the soil slightly moist but not sopping wet and do what you can to optimize their growing conditions to help them recover. If the plants lost a lot of roots, you may want to trim the tops back a bit to compensate. Good luck with the operation!
Q&A Library Searching Tips