Time their troubler is

But were it not that time their troubler is
All that in this garden grows
Should happy be and have immortal bliss
For here all plenty and all pleasure flows

I came across this inscription on Wednesday, carved into the backrest of a garden seat in County Meath. The setting so justified the sentiment that I was curious, and asked around; but no-one seemed to know the verse's provenance, and since coming home I've tried all my reference books, and of course Google - but so far nothing. I assume it's original, perhaps a family member's private musing, but if anyone knows otherwise..