This is my transcription from an actual recording on Spotify. It has some significant differences from the version posted by Autoharper above.

SING IN THE SPRING
As sung by Utah Phillips on "Starlight on the Rails: A Songbook" (2005)

1. I had a mule and his name was Jack.
I had a mule; his name was Jack,
And when I climbed upon his back,
He damn-near died of a heart attack.

CHORUS: Sing in the spring; sing in the fall.
Sing when you hear my baby bawl.
Sing all day, all night too.
If you hush your cryin', I'll sing for you.

2. I had a canary all yeller an' green.
I had a canary all yeller an' green.
Stupidest bird you've ever seen,
It could swear like a big marine.

3. I had a horse and his name was Tex,
I had a horse; his name was Tex,
Signed his name with an X
And made his livin' forgin' checks.

4. Had a little lamb I used to keep,
Little bitty lamb I used to keep.
When I'd tell 'im to go to sleep,
Counted people instead o' sheep.

5. Oh, then I got a tall giraffe.
Then I got a tall giraffe.
Liked to sing an' he liked to laugh,
An' lived on beer an' bubble bath.

6. I had ev'rything short an' tall,
Done had ev'rything short an' tall,
Round an' fat, big or small.
Guess my baby's the best of all.