Answer: Although called "dwarf" and with an approximately conical shape, these plants can ultimately grow quite wide as this is their natural form.
In the spring, you can nip off about one-half of the new growth while it is in the "candle stage" (meaning the tip of the branch has small immature needles packed around the stem and it looks a bit like a candle). This will make the plant grow denser and control the size somewhat, but you would still see an inch or two of growth per year. Do not cut back past the new tips or cut into the old wood because this will result in ugly bare cut branches that will not grow back.
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