Good one, Dave! The poem captures in simple language a human experience ten thousand years old. The reference to your mortality after referring to the mortality of weeds on weeding day is particularly effective, as others have remarked. A very satisfying poem, this coming from someone who has spent hundreds of hours weeding over the years.
I’m reminded of Henry Thoreau’s passage in Walden concerning his thoughts about weeding his bean-field: “Many a lusty crest-waving Hector, that towered a whole foot above his crowding comrades, fell before my weapon and rolled in the dust.”