Here is the link for the video on YouTube on how to test for starch.
1. Kill the leaf by immersing it is BOILING water for 2 minutes
2. Place the leaf in a boiling tube of alcohol and then into a beaker. It is to remove chlorophyll.
3. Pour away alcohol and immerse leaf into hot water for the last time (10 secs). It is to soften the leaf and thus making it more permeable to iodine solution
4. Place the leaf on a white tile cover the WHOLE leaf with drips of iodine solution.
5. Observe and conclude: 1. If starch is present, leaf will turn blue-black. 2. If starch is absent, leaf will remain brown.