Most plants guides are driven by flowers; at this time of year they begin to lose their effectiveness. In the case of the Common Burdock, Arctium minus, it's too late for this biennial thistle. Luckily, I have a copy of A Guide to Wildflowers in Winter by Carol Levine and illustrated by Dick Rauh. It's dog-eared from last winter and soon to be my main guide once again. (Here's an earlier post with Burdock in flower.)
Common Wayside Flowers:
The common burdock, so plentifully strewn along our waysides, and which is universally known, not only by its dullpurple flowers and immense leaves, but also through countrychildren throwing them at one another, and finding great amusement, too, in covering a stranger's coat with the "burs," is another great disperser of seeds. These burs, with their bristly heads, cling to the fur or wool of animals, and to everything to which it is possible to cling, and so are carried abroad, and cast very often on land where they were before very rare, to the great grief of the farmer. We have heard— though we trust it is not true — of farmer-men, who, having a spite against their masters, have filled their pockets with thistle-down, and scattered it over newly-ploughed land, that had been prepared for corn, and which, to the farmers' great grief and loss, produced only a crop of thistles, after it was sown with wheat. A gallows high as Hainan's, and the mercy carrion crows would show the hanging body, would be meet punishment for such rascals, if such indeed there be.
Miller, Thomas. Common Wayside Flowers. London, New York, 1873. 85-6. Web. Google Book Search. 10 Oct 2009.