The August morning is thick with haze and heat above which even the height of Mill Mountain cannot rise.

A half-dozen or so tiger swallowtail butterflies flit between buddleia blooms in the garden ringing the Discovery Center atop the mountain.

It’s a working breakfast for the butterflies; their pollen-collecting feet tap from one petal to another as they uncoil proboscises at each flower to sip nectar as if it were a morning latte.

Beneath the butterflies’ labor stoops Kathi McAteer with work of her own.

“I love pulling weeds,” says the retiree, who with her husband, Bill McAteer, spends a couple of mornings a week dead-heading, raking and, of course, pulling weeds in the garden.

As families of zoogoers, cyclists and hikers pass, the pair labors in anonymity, her bleached straw hat and garden gloves covered with a fine soil-brown patina, evidence to the commitment of their volunteerism. The garden always needs tending: Work completed only a week ago needs attention again, she notes. Weeds sprout overnight. Bushes spill over pathways as soon as backs are turned. Still, it makes her feel good. It teaches patience, too, she says.

The butterflies — with lives dedicated to the blooms — already seem to have mastered the virtue through accidental tending of the garden, their productivity merely an afterthought of the pursuit of food and life.

The McAteers and the insects are co-laborers who move effortlessly in their rhythms here: The butterflies taste each bloom again and again, and the couple — comfortable and quiet in the way only those married for years can be — dig and pull and clip and prune.

And so the garden is tended.

A passing boy once remarked that Kathi must be rich to be able to do such work and not be paid.

“We are,” she said, gesturing to the overabundance of life and color nearly enveloping the center before bending back down to the honest work of pulling weeds — nectar for the soul.