You can use the leaves and stems or compost the stems.

Comfrey grows tall when it flowers, that's all.

Hi to answer in a very simple way,

(1) Comfrey will grow tall and if in a shaded area you'll find its happy to get good strong leave's and a good think stem.
(2) REF the use of this plant,

(a) compost use the complete comfrey plant can be and is used to compost, it's one of the very best composting plants and you put as much as you can get your hands on
onto the compost heap

(b) to make a liquid fertilzer for your garden,

Ive a 45 gal/drum, make sure its clean of what ever was once inside the drum,
The one i use was once an oil drum and i lit a fire inside it to burn away any old oil,

You fill an old sack with as much comfrey as you can get inside it and also some form of a weight 'brick or rocks to help sink the sack,
if your finding problems getting a sack then use the net bags used for holding onions "the super market are a good place to get these.
You will need two large onion netts, again fill with comfrey & a weight and sink in the drum.

Leave for 4 TO 6 weeks and then water wouls turn brown,
the mix is 1 part comfrey mix to 9 parts water.

It's a well tried & tested way of making a very good fertilizer.

Thanks very much once again for the info, I now know exactly what to do - and I have even made 1 comfrey poultice ready for any emergencies !

Better used fresh though Hank! Hope you don't need it.

It's been in the freezer for a while, is it no good now ?