I got your question in an Oooby email but it doesn't seem to link to where you posted it so I am starting a new discussion. Hope you find it.
Use branches of Wormwood (Artemisia absinthium)
Grows wild on lots of roadside banks.
Thanks Elisabeth, much appreciated.
the other approach is to freeze 'em out. you can slide one or two frames at a time into your freezer, then stored in airproof box. or find a business with one of those giant walk-in fridges.