In terms of result for time, they’re very productive. Once they’re in the ground the only thing you need to do is to water if dry and weed a couple of times.
Trimming Leeks when Planting Out
You may read in some older gardening books about trimming the roots and tops before planting out but trials have shown this is pointless and may actually harm rather than help.
If you’ve got a heavy clay soil, leeks have a benefit that they break up the clay with their root system. Do give a little fertiliser, I like fish, blood & bone, before planting out to get them off to a good start.