I have listened carefully to two versions that Gracie Fields recorded, and I don't hear her extending the first syllable of "aspidistra." What she does do, however, is hesitate slightly before "biggest" and then pronounce it with an explosive "b," to great comic effect.

You can hear Gracie Fields' original recording (from 1938?) at YouTube.
another copy followed by SINGIN' IN THE BATHTUB on a 78-rpm EP record.
A piano is the only accompaniment in this version.

I have compared the recorded version to the words that Gargoyle posted, and boldfaced the differences. I have also grouped the lines in a way that makes more sense to me. Now there are only 2 kinds of stanzas: a 6-line verse with the rhyme scheme xaxaxa, and an 8-line chorus with the scheme bzbzcccz, where z is the repeated title.


THE BIGGEST ASPIDISTRA IN THE WORLD
Words and music Will E. Haines, Jimmy Harper and Tommy Connor
As sung by Gracie Fields

For years we 'ad an aspidistra in a flower pot
On the whatnot, near the 'atstand in the 'all.
It didn't seem to grow 'til one day our brother Joe
Had a notion that 'e'd make it strong and tall.
So 'e's crossed it with an acorn from an oak tree,
And 'e's planted it against the garden wall.

It shot up like a rocket 'til it nearly touched the sky.
It's the biggest aspidistra in the world.
We couldn't see the top of it, it got so bloomin' 'igh.
It's the biggest aspidistra in the world.
When father's 'ad a skinful at 'is pub, 'The Bunch of Grapes,'
He doesn't go all fighting mad and getting into scrapes.
You'll find 'im in 'is bear-skin [or "bare skin"?] playing 'Tarzan of the Apes,'
Up the biggest aspidistra in the world.

We 'ave to get it watered by the local fire brigade,
So they've put the water rates up 'alf a crown.
The roots stop up the drains, grow along the country lanes,
And they come up 'alf a mile outside the town.
Once we 'ired the Crystal Palace for an 'ot-house,
But a jealous rival went and burnt it down.

The tom cats and the moggies love to spend their evenings out
Up the biggest aspidistra in the world.
They all begin meowing when the buds begin to sprout
Up the biggest aspidistra in the world.
The dogs line up for miles and miles, a funny sight to see.
They sniff around for hours on end and wag their tails with glee,
So I've 'ad to put a notice up to say it's not a tree.
It's the biggest aspidistra in the world.

It's getting worn and weary and its leaves are turning grey.
It's the oldest aspidistra in the world,
So we water it with 'alf a pint of Guinness ev'ry day.
It's the stoutest aspidistra in the world.
The borough council told us that we've got to chop it down.
It interferes with aeroplanes that fly above the town,
So we sold it to a woodyard for a lousy 'alf a crown.
It's the biggest aspidistra in the world.

[There's also a later recording (from 1940?) with an orchestra accompaniment and this new verse:]

Me brother's in the Army. He's in the 'Ome Defence,
With the biggest aspidistra in the world.
The colonel says at Topping(?) now we'll start the big advance,
With the biggest aspidistra in the world.
When Goering sees it from afar, 'e'll say to his old frau,
"Young Joe 'as got his blood up. War will soon be over now,
For they're going to string old 'Itler from the very 'ighest bough
Of the biggest aspidistra in the world."

[I couldn't find a place called Topping. Am I mishearing it?]