we planted hundreds of willows and poplars last year, poplars are now 5ft high, planted them close together to make a hedge. the willows arent far behind in height. the ones that were planted through black plastic (which was weighed down with manure) are 3 x the height of the ones that were put straight into ground.
unfortunately a pony leant over fence and ate a few of the poplars down quite low so im hoping they will regrow.
we used bowhayes and were happy with them but u cud prob get cheaper. also someone recommended alder for wet areas, though never tried that one.