My idea...if you are going to throw a plastic bag onto driveways. Don't include a rock for weight.
Why not include a gladiolus bulb? Include growing tips and instructions for planting of course.
Naturally you will want to mention what a great flower it is. And how to get more bulbs.
And maybe there is a way to throw the brochure--without a plastic bag. Someone think of a way to eliminate the bag.