Yeah unless someone comes up with a convincing story otherwise,
then I am pretty sure this is just a silly play on words.
People go
".. in for a quick drink" to the pub,
or
".. in for a quick swim" to the pool, etc
Obviously gardening is an odd word because nobody ever says "I'm going for a garden"
it just sounds silly. It is almost always used in the gerund form, i.e. -ING
You say drinking, and, go for a drink,
swimming, and, go for a swim,
playing, and, go outside and play,
So "In for a quick garden" is just a silly sentence.
There was a motorbike race once,
one of the riders lost his line and went off the track,
after tearing up the grass for a while he managed to get it back on course .
The commentator said, "... he rejoins the race after 150 yards of frantic gardening!"
Sorry, not a word of Zeppelin expertise involved in this post!