My maternal grandfather, gone these many years, was a man of Old South propriety — not the sort who would normally think about leaving the house without being properly dressed.

But returning home after one of her first dates with my dad, my mother was mortified to find her father standing out in the yard, flashlight in hand, wearing only his undershirt and boxer shorts.

He was inspecting his night-blooming cereus, a plant that, true to its name, blooms only for a few hours after dark. The cereus waits for no one, and my grandfather, eager to catch the show, had scooted out for the plant’s performance without throwing on his trousers.

All of this came to mind last week when we had a nature moment at our house that prompted its own wardrobe emergency. My wife planted dill this summer to attract swallowtail butterflies, who count the herb as a major delicacy. I’ll never understand how swallowtail caterpillars so quickly find dill after it’s placed in the ground. But in no time, the big terra cotta pot near the front door where we have our herb garden was swarming with exotic crawlies — fat caterpillars, as bright as brooches, in shades of black and yellow that seemed worthy of Disney.

Within days, they’d made short work of our dill, cleaning many of its stems of the fragrant, feathery leaves we like to crush over grilled fish. Imagine a hairbrush reduced to its handle, and you’ll get some idea of how our dill looked after the caterpillars consumed their all-you-can-eat buffet.

Just enough foliage remained to camouflage the tiny cocoons that clung to the stems, little green vessels cleverly designed to resemble a leaf.

My wife checked the cocoons often, hoping to catch an emerging butterfly before it took flight. But nothing short of a continuous vigil — an impractical pastime for a career mom — seemed likely to yield success.

Then one morning last week, while stooping to leash the terrier for his walk, I caught a small flash of black in the corner of my eye. Over in the dill, a butterfly, fresh from its cocoon, was slowly fanning its wings to dry them for their inaugural run.

I quieted the dog, and we stood there on the stoop, as motionless as the figures in a creche. The butterfly was a wonder — black, orange, indigo blue, a brilliant, breathing bit of stained glass. Reaching back and softly rapping on the door, I beckoned my wife, who emerged with her camera, still wearing her nightgown, not quite ready for the audience of joggers who run by our driveway each morning. But there was no time to change before the butterfly flew away.

My wife snapped a few shots, and I’m including one with today’s column. Somewhere, I suspect, my grandfather is smiling.

Danny Heitman is on Twitter, @Danny_Heitman.