Donated Raspberry Canes

The tall one's sound like Autumn canes so you will need to prune them down to 6 inches high and they will fruit this year. Any shorter ones might be early fruiting so i would leave these un-pruned as they fruit on last year's wood. I would not underplant with anything as the the suckers from raspberries can spread quite far from the mother plant. As to fertiliser, a hand ful of bonemeal to each planting hole then a liquid tomato feed when the fruits first appear.

My autumn ones get a bit taller than that, (either that or I'm very short and MoS is very tall), but yes, my summer ones are far taller, that's why they need staking and the autumn ones don't.

This from the BBC
http://www.bbc.co.uk/gardening/basics/techniques/growfruitandveg_growingraspberries1.shtml
gives advice for building a support system wired up to 66in high - but says there is no need for the top wire for Autumn varieties, which implies they are shorter than that 

It would all boil down to plant vigour, I presume - but my neighbours summer fruiting are about 8ft tall  :blink:

My autumn bliss are normally between 4ft and 5ft tall