When writing a thank-you poem for your mother, emphasize specific things she has done for you and attributes unique to her to highlight how grateful you are. Thank-you poems can take any number of forms, including acrostic, haiku, free-form, ballad or visual.
For the less poetically inclined, an acrostic poem, often referred to as an acronym or name poem, is an easy way express gratitude. Combining the first letter of every line of an acrostic poem spells out a word or phrase. You can customize your poem by using your mother's name or the words "mother" or "Thank you" as the first letters of your poem.
Poems do not need to rhyme to be linguistically beautiful. The real impact is in the meanings of the words used in the poem. The content of your poem can include a memory of time your mother sacrificed for you or time that the two of you enjoyed together. Focus on the aspects of her personality that make her special. Being a mother is a very demanding job, so acknowledge the hard work, patience and strength that being a mother takes.
When your poem is finished, you can take it to the next level by using artistic lettering or designs to make it special.