Question
Do you know of an organic way -- no chemicals -- to get rid of or at least to avoid "catching" wild onions in the lawn?

I have a friend who has them everywhere and I thought I would know a solution. But I can't find them anywhere.  I dig mine up which is annoying but after cutting the grass it is hard to tell where they are.

Answer
Wish there was a better answer than this, but there are only two ways I know of to get rid of Wild Onion ('Allium canadense' to botanists).

First is the old straight boiling vinegar method, which seems more trouble than it's worth.

Second is the old fashioned hand weeding method.  This is not reliable because it's very easy to miss a bulblet.

Clemson University Cooperative Extension posts a cheat sheet on 'Wild Garlic & Wild Onion':

http://hgic.clemson.edu/factsheets/HGIC2311.htm

'must be treated with a postemergence herbicide, and persistence is the key. Plants will need to be sprayed more than once and for more than one season. One characteristic that makes control difficult is that both have a thin, glossy leaf to which herbicides don抰 readily adhere. Adding a spreader-sticker to the spray solution will help it to adhere evenly. Be aware that some products have a spreader-sticker already added. Unlike most weeds, mowing wild garlic or wild onion immediately before applying an herbicide may improve uptake. After application, do not mow for at least two weeks.'

Clemson posts a bunch of chemicals I would not touch with a 10 foot pole.  They're working on this problem.  And close.  But no cigar.  Sorry!