To see Crocus sieberi, one of Crete’s most beautiful endemic flowers you will need to go quite high up in the mountains.
This spring crocus flowers right at the edge of melting snow. You might find it as low as 1300m in March or early April and all the way up to the higher summits (2300 or 2400m) at later times like May or June.
Your guide to finding the flower in bloom is to look for areas where snow has recently melted. With a bit of luck (actually, it’s not really luck but the right timing) you can find whole hillsides covered in crocuses.