If the stem is in the range for the whole plot, then, yes, you would include it. If it is outside the range then there's no point in including it. If, for example, all the data was in the range 200 to 849 then you could have a stem based on the first 2 digits of the data: 20 to 84. If there were no data between 500 and 600 you would still include 50 as a stem so that you get a proper picture of the data organisation in the range. But there would be no point in including 10 or 90 as stems because there are no leaves for these stems.