How do you say my beautiful mother in Japanese?

Informal:

Male Usage: 僕のきれいなお袋 /bo ku no ki rei na o fu ku ro/

Female Usage: 私のきれいなお袋 /a ta shi no ki rei na o fu ku ro/

Formal:

* Male/Female Usage: 我が美しい母 /wa ga u tsu ku shii ha ha/

[*Note: Only used referring to your mother as third person, in her absence. If you are using that to call out to her like in a writing it would be: 我が美しいお母さんよ /wa ga u tsu ku shii o kaa san yo/.]