There’s a couple of things to consider: time of day and type of vegetation. You want to shoot when there’s a lot of sunlight. Usually mid-day when the sun is high in the sky. The subject needs to be fully exposed to the sun. So don’t shoot stuff that is in shade. In my experiments, I have found that not all type of vegetation will turn white. Some will stay dark. You just have to experiment for yourself to see which ones work.

After the shoot, you need to edit the photos in a photo editing where you can change color channels. Here’s a link to a tutorial that explains it pretty well: http://www.tutorial9.net/photography/infrared-photography/

Good luck!