Summer begins with the appearance of the butterflies. The weather warms, and suddenly there they are, swirling past, on their way to court, mate and frolic.
For the most enraptured gardeners, the spectacle is so thrilling that they've ripped out plants that they like and re-landscaped with plants that butterflies need. Where once gardeners fought caterpillars with insecticides and thistles with weed killers, now they coddle worms and pamper weeds in an effort to nurture the splendid winged adults.
They are part of a growing breed: butterfly gardeners. For them, butterflies are more than an air show. They are a measure of the most profound seasonal tempos. No animal's survival and habits are more directly bound up with the life of plants.
As with so many horticultural trends, butterfly gardening came out of England. It first took hold here in the early 1970s, led by the Xerces Society and the Sierra Club, says Julian Donahue, assistant curator emeritus of the Natural History Museum of Los Angeles County and for 23 years the man in charge of the moth and butterfly collection.
By 1976, Donahue was publishing articles in botanical journals urging gardeners to create habitats.
"Butterflies are coldblooded. They need heat to fly," he says.
In the butterfly house of the museum, he reaches for a monarch, gently gripping it by its body so it doesn't fly away (don't try this at home). Children gather around him. They can smell a good teacher. Plus, he has what seems a godlike privilege: He's the only person allowed to handle the insects.
"The original butterfly gardens only had nectar plants," he says. "These are great for butterflies. But then people realized that butterflies don't materialize out of thin air. You really have to have what the butterfly caterpillars eat."
To know what to plant, it helps to understand the life cycle of butterflies, he says. They are first deposited onto plants as eggs, out of which hatch tiny caterpillars. The first thing an emerging caterpillar eats is its shell. It then proceeds to eat 20 times its body weight in leaves. These little "self-stuffing sausages" will shed their skins five times before it's time to transform yet again, into pupae.
Pupae are intermediate beings, not caterpillars, not butterflies, but tightly packaged gobs of protoplasm called chrysalids. These can dangle from a plant or the eave of a house, or nestle among leaves and grass.
Only the sharp eyes of entomologists, kids and predators can usually spot them: 150 million years of evolution have equipped them to look almost exactly like dead leaves. Inside, winged butterflies will be forming.
When adult butterflies emerge from these cases, they are drowsy and damp. This is the time when they are most likely to settle on us, pose for a photograph, bask on a flower. Once they are on the wing, it's all business.
"If they're males, they're looking for females," Donahue says. "If they're females, they're looking for food plants where they can lay their eggs."
Butterflies are promiscuous, but also strict practitioners of family planning. The females will mate repeatedly, then store the sperm separately from the eggs. They fertilize the eggs only when they've found a spot suitable for their young.
Finding the right plant can amount to an exhaustive shopping trip. Most butterflies will lay eggs on only one or two types of plants. Red admirals like nettles; monarchs like milkweed; the eastern black swallowtail likes Queen Anne's lace.
How do these little bugs find the exact plants that they need in our big crazy urban grid? "They're really good botanists," says Donahue. "They can detect a food plant by infrared radiation of the plant or by the smell. Every plant has a chemical signal."
What we take to be the same butterflies throughout the summer are probably several generations. Most adults live four to eight weeks. The butterfly you see in your garden is probably the insect equivalent of Lassie, replaced several times before the series ends.
"One of the best friends of butterflies is a lazy gardener," he says.
Letting the fennel go to seed and lamb's-quarters run amok is creating a breeding ground for many butterflies. If you leave leaf mulch, don't use insecticides and don't cannon-blast plants with hose water, you are more likely to have butterflies.
As for good nectar plants, those are easy. Evolution made butterflies picky about caterpillar plants, but adults will drink nectar where they find it. Shape is the important factor.
While hummingbirds can suspend themselves in air to drink from tubular flowers, butterflies need a flat, upward facing flower that they can hold on to.
Native yarrow, thistles, daisies, zinnias and marigolds, and buddleia and milkweed are all excellent nectar plants. The classic plant, buddleia or butterfly bush, has a light sweet fragrance, very like drugstore perfume. Lore has it that butterflies are partial to yellow.