July begins the big payback in my garden. I'm more or less finished with planting and potting. The endless fretting about which plants to put where is over. Dollars spent are, well, dollars spent. Gone. I'm cash poor and bills are overdue.

But who cares? My Velvet Queen sunflowers are waist high, tall as a child and too big to be bothered by birds and cutworms. Ha-ha. The joe pye weed in the back border has recovered from the bug problem that plagues it every May; it's as stout and muscular as ever and about to knock my socks off in August with heavy heads of dusky pink blooms. The bed by the guestroom is overflowing with Impatiens glandulifera, a thrilling plant from the Himalayas charmingly known as "policeman's helmet." Four feet tall by now, these annual plants will touch my house's roof edge (I kid you not) by August and blossom like mad with pale pink, orchid-like flowers that bumblebees flock to. I adore this Jack in the Beanstalk plant. The seedlings, in early May, were the size of a dime (not even). Then a nickel. Then a quarter. Now, suddenly, they're fat and brawny, lush and leafy. Cell division! Heat! It's all too wonderful for words.

Impatiens glandulifera is one of many self-sowing, or "volunteer," plants in my garden. Volunteers bring spontaneity and spirit to a garden with their carefree ways. They are plants that walk right in and sit right down. Unfortunately, most of them, once they get a foothold in your garden, tend to barge in and take over. This won't do. If they are not ruthlessly thinned they will take over like drunks at a party and hog the floor. I thin my volunteers gradually, beginning in spring as soon as they are large enough to handle - an inch or so tall with most varieties. It's overwhelming at first to see thousands of tiny seedlings and think of reducing them in any sensible way. I start by zooming in on strong-looking ones and those I deem to be in particularly good places, clearing away all others a few inches around them. As the season progresses, I whittle away at the volunteers until only the best and the brightest are left standing. As with all things in the garden, each volunteer has a role to play in the grand scheme. Certainly, not every single one is utterly precious, but their collective impact is of great importance. I think of my volunteers as common threads weaving the big picture together.

Kochia scoparia is another volunteer in the garden. This peculiar species, a member of the goosefoot family, looks a bit like Cousin It from the Addams Family. It's a dense, bullet-shaped plant with narrow, stringy leaves that turn cranberry red in autumn. Kochia (common names include "summer cypress" and "Belvedere") grows about three feet tall or less and is happiest in full sun and average, well-drained soil. Visitors to the garden find this plant irresistible to touch. Its solid, static form is an excellent foil in the garden where so many plants are frothy and loose. It's dignified and serious, goofy and fun, all at the same time.

Verbena bonariensis is a subtle beauty and an essential component of my gardens. It's one of the ten best garden plants in the world. (I haven't the foggiest idea what the other nine are.) This elegant plant has pencil-thin stems and small clusters of tiny purple flowers. It's a tender perennial that can be treated as an annual, flowering the first year from seed. A cinch to grow, it likes sun or light shade, rich or poor soil, and never needs staking or deadheading. Because it's so airy, Verbena fits itself into almost every situation with ease, growing among other plants and dancing about them feather-lightly, while lifting its mildly scented blooms effortlessly into the air. It's wonderfully see-through, able to grow smack in front of shorter plants without hiding or upstaging them. Every spring, when thousands and thousands (I am not exaggerating) of Verbena seedlings pop up in my garden, I think I'll pull my hair out. In July and August, when butterflies and hummingbirds flock to it, I couldn't care less about my hair. I call this plant the Audrey Hepburn of the garden, because of its charm and grace.

I have a big volunteer army: golden feverfew, lady's mantle, cleome, love in a mist, poppies, spurge, honesty, perilla, orach, and others. Sometimes I wonder where I would be without all my helpers. I put them here once and now they put themselves wherever they please - in cracks and crevices, in nooks and crannies. Yes, they require major taming to keep them in line; it's an editing process, a spring chore that seems endless at times. But these willing plants, scattered about the place, give the garden a settled, mature look that is worth every ounce of effort. When a visitor admires my volunteer plants, I simply send them away with a bucket of compost. "It's full of seeds of everything you see." I don't tell them to get ready to pull their hair out come spring. No pain, no gain. But there is always the payback in summer.