If you use a marker on sticks, put clear nail polish over them. Actually pencil works better as all markers fade over time.
I have used tongue depressors and found on some, nothing written on them at all. It was very disappointing, especially since I was growing some special heirloom tulips in pots.
I have been told that tulips don't "come back" in pots, but mine have.
Also daffodils....
