What are they for?

They are for the event items. One is released every day except for the last day of the event. ^^

Twisted Child Eve, answered your question, so I'll just add to it.

The buds, that will also appear on your screen are for event shop items. They are the equilent of 25g and only available for use during the event, and for the event commons.

I dont know if you seen the FAQ,but the first 10 orchids get you the flower crown,I have it on now.And the second 10 gets you the orchid petals,also on me.:) I dont think the 3rd clue has been released yet.*Anxiously awaits*

PS-I just plucked a orchid off of Vampyre.YaY!

All the answers you need can be found in the Event FAQ.
Read through the first page, and post your questions there if you're still confused.