I can't find any good poems about mothers, so I read some poems that I heard very often from my mother:
A Child's Garden of Verses
Robert Louis Stevenson
I did try a little bit to find the bizarre lenticular edition of the poems that I remember--so seventies--and had greater success than I expected. I found no mention of that particular book, but plenty of the genre, at this fascinating site: Stump the Bookseller.