From the sheet music at the National Library of Australia:

GROW, LITTLE MUSHROOM, GROW
Words and music by Tom Mellor, Alf. J. Lawrance and Harry Gifford, ©1906.
"Sung with great success by Miss Elsa Langley."

1. There once was a frog and he would a-wooing go,
With another little frog he knew;
And he happened to stray in a field one day
Where a wee little mushroom grew.
Said he, "What a nice cosy home you'd make,
Affording a shelter free;
And if it is right that you grow in the night,
I will bring my bride with me.

So—

CHORUS: Grow, grow, grow, little mushroom, grow.
Grow, grow; somebody wants you so.
I shall call again tomorrow morn, you'll see,
And if you've grown bigger you will just suit me,
So grow, grow, grow, little mushroom, grow!

2. That evening he told his sweetheart what he had found.
"It's a model little home," said he,
"For the comforts are that of a ground-floor flat
That will just hold two—perhaps three."
So they made all arrangements to go next day
And live in this home so cheap;
Then all through that night in a dream of delight,
He was murmuring in his sleep: CHORUS

3. Now early next morn came an urchin who had seen
This mushroom of minor size;
Then the frogs made a call, but indeed felt small,
For the youngster had claimed the prize.
As the frog searched about with his lady-love,
In disgust she remarked, "It's plain,
Your home, I declare, was a castle in the air,
So it's useless to explain." CHORUS