Answer: The traditional method of propagating this plant is by dividing it in very early spring just as the new growth appears. To do that, simply dig up a portion of the plant, being sure to take both top shoots and their correcponding roots, then replant at the same depth as it grew before. A piece about six inches across will make a nice plant.
This plant is naturally leggy and may flop over , especially if it is not growing in full sun all day long. To prevent this, you may stake the plant. Another approach is to cut it back lightly when it is about a foot high. This will cause it to grow a bit denser and shorter, but will also delay the blooming. Some varieties will be floppier than others regardless of what you do or don't do.
As to whether or not the trimmings will root in water, you could always try it and see what happens.
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