For additional info and leads, see this entry at folklorist.org:
http://www.folklorist.org/song/Watercresses
In particular, the entry provides two verses from some version titled "The Dairy Farmer" and points to a version called "Watercrest" and another in the Warner collection, which may be online; I haven't checked.

In an book review (1986) by Edith Fowke of The Greig-Duncan Folk Song Collection Vols. 1 and 2, she mentions that many of the non-Scottish songs in the second volume are also found in Ontario, including some rather rare ones, "Bunch of Water Cresses" being an example. So there's another version you may be able to find.
[ URL for book review: http://cjtm.icaap.org/content/13/v13art8.html ]

-- Artful Codger