A box and whisker plot is a graphical method of displaying variation in a set of data. In most cases a histogram provides a sufficient display; however, a box and whisker plot can provide additional detail while allowing multiple sets of data to be displayed in the same graph. Some types are called box and whisker plots with outliers.
Can you compost Leylandii branches and hedge clippings - Yes. We were quite surprised to learn some experienced composters advise not to add Leyandii cuttings as they are apparently too acidic. Composting bacteria can remain active in all but the most acidic conditions.
Grow new plants of comfrey from root cuttings or crown division from healthy vigorous clumps. This just means that if you dig up a clump, new plants will grow from almost any piece of root separated from the main clump. Alternatively drive a spade through the clump to divide it.