Hi Lissie, thank you for sharing this great idea. I have been using Crocs to garden in ( I know a fashion fopar!!) but I do find that the soil and any dew on the grass does get through the holes and onto your feet. Also the tread does seem to track dirt into the house.
You have saved us all lots of money. Check out these rubber ankle boots for gardening
http://www.spats-boots.co.nz. I think your version will be just as dapper and will not cost $99 plus postage.
Now all we need is some inventive person to come up with an idea to use the leg cutoffs from the gumboots?