A Little Bit of Sunshine

Out this afternoon up past Dunblane we parked up and took a walk up a narrow country road. Along the way is an old abandoned farm house with lots of snowdrops decorating the roadside and this stunning group of yellow crocus. Simply dazzling in today's bright sunlight.
Question: is the plural crocii, croces, crocuses or what? Answers please on the back of a £20 note.