WillC said:Jades rarely if ever need repotting. <snip!> Unnecessary repotting is the single most common cause of plant problems
This is untrue and unhelpful. How do you think your jade plant ended up in the pot it is in? It had to come from somewhere. I repot a dozen plants a week without any problems whatsoever. Perhaps if I explain a bit, the thinking will become clear. There is absolutely no reason to have a phobia of larger pots or regular repotting. These are useful tools and techniques. You need to know the right time and place, but that's true for anything in the garden. Repotting is something to do when a plant is growing well and getting large for the size of the pot, not usually a great idea when a plant is in crisis or somehow suffering from a serious health problem.
First, one thing to bear in mind is that most succulents are slow growing plants. They take years to reach a good size. Jade plants are no exception. They do not need any kind of frequent intervention to do just fine. But they will slow down and reach a point of frustration when the pot size is too small. After several years there is a very real growth arrest. I would invite anyone who's curious to do the simple experiment of placing a small pot alongside a larger pot, let two plants grow alongside each other, and observe what happens to the plants over the course of months to years. I do these sorts of experiments constantly (not usually on purpose) because I make every effort to use the smallest pot possible for my plants (see below).
Second important point is that there are different ways to repot plants, and they are not equal. The simplest repotting (what I would do for a jade) would be to remove the plant from the pot it's in, with the root ball completely intact, and drop it in a bigger pot with more soil. This would be the most noninvasive route, and it leads to absolutely no disturbance of the health of the plant. A more involved repotting might require the loosening of the roots and the removal of the soil, and this is where you have to bear in mind that injured roots (an inevitable part of this more invasive process) are sensitive and need time to recover. So you want to leave them alone in their new pot without watering for a week or more. When in doubt, choose this route. If you consider the plant in human terms, the last thing you would want to do with an open wound would be to soak it in dirty water. But these are most resilient plants and they will recover very nicely in a couple of weeks. Watering prematurely, not the repotting itself, is the source of danger.
Third, and this is at the core of the question of when to repot, healthy jades and other succulents will follow a natural course of growth in containers. They burst out at first in new soil, then slow down as the part above ground gets larger, and eventually reach a sort of equilibrium where they are only putting out as many new leaves as they need to keep going. There's a certain kind of fetish in the succulent community relating to small pots, and you will see lots of succulents in bonsai pots at plant shows. Some plants really do thrive under these conditions, because they make shallow roots and enjoy frequent water. Other plants are less malleable, and they may look great in a tiny container but they don't do much growing in it. Jades are large shrubs in the ground here and they fall into this second category. When in doubt, consider the growth habit of the plant and its eventual size in nature when you are trying to decide on what size pot to use. A plant that never gets big in nature will never require a large pot in cultivation.
Fourth, and related to why I always try to use the smallest pots practical in my own growing... there is a cost issue related to pot size which is good to bear in mind when the numbers get big. Every jump in pot size (say from 4" to 5" to 6") comes with a doubling of the volume, more or less, which means twice as much soil fits in the space. So by aiming on the small side, you can save a lot of money. The downside is that when you do this, you have to be hyper attentive to the needs of the plants, and when they are genuinely being held back by the size of the container. More frequent repotting. In many cases you will get a bigger plant sooner if you put one in a large pot to start with, but that's a price I'm willing to pay to save money. This relates to the question of "necessary", which is just as flexible a term as you can imagine.
Whatever pot you use for any given plant, the critical relationship is the one between the size of the roots and the size of the container. This relates to watering frequency. When there's a good fit (not too loose not too tight) the soil will dry out relatively quickly, and you can water relatively often, waiting until the soil is dry or almost dry each time. When the roots only occupy a small fraction of the soil volume, the pot will hold onto water longer. The danger there is that if you're not careful, you can easily overwater a plant in that situation, which results in the bottom staying wet all the time... something jades do not enjoy. Overwatering is the real danger. You can manage a wide variety of pot shapes and sizes if you know when is the right time to water.
Strong light (hours of sun indoors) makes watering easier and results in a better looking plant.
