Plant that's difficult gardener is going to put in fine soil, initially (9)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

MARY’LL (the gardener is going to), is put inside AI (A1, fine) S[oil]. But what is the ‘difficult’ doing? Amaryllis is an easy plant to grow, ours has been sticking up enormous stems and red blooms regularly for years.