Feeding A Argentina Butia.
February is a good time to start in the UK we would suggest a handful of Growmore fertilizer spread around the base of the plant about a metre square in area and then if its dry water it in.Then in later April start feeding with a liquid tomato feed this contains high levels of potash.Feeding with the tomato feed once every two weeks through to the end of August.
Some garden centres will try to sell you some expensive feeds but the ones we have recommended and not very expensive and will be fine and keep the growth stable and not to soft so in hard winter the plant will not be to effected by frost etc.