The stem strengthens in time plus they put out air roots that thicken and help support the plant. But they do stay wider than tall unless you prune pretty heavily. Otherwise they are known to loose large branches or sometimes even topple over when they get quite large. The only thing I can think of is to surround them with 4 little supports like you see done for young trees. But I still would not expect it to get very tall.

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My jade never knows what season it is because I keep her indoors. But she does quit growing and that's when I know to cut way down on the watering. This usually happens about twice a year.

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