In pots or in the ground? I'm going to assume in the ground - the best fertiliser is a 2 inch deep mulch of well composted animal manure or garden compost in about April or May, when the soil is already moist. Otherwise, apply a general fertiliser such as Osmocote or Growmore around the base in April and again in early June. You can do both if you like, both the mulch and the chemical fertiliser, but put the chemical fertiliser under the mulch. Do not feed at this time of year.

See responses to your earlier question.