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These butterflies are sure sign of autumn

Thousands of Orange Sulphur butterflies looking for clover

Sacramento Digs Gardening
BY Debbie Arrington PUBLISHED SEP 29, 2021

The Orange Sulphur butterfly often lives in alfalfa fields but disperses when the crop is harvested. (Photo courtesy Art Shapiro's Butterfly Website)

“Where did all these yellow butterflies come from?” My neighbors want to know.

Out of nowhere, thousands of brightly colored little butterflies suddenly appeared this week in Sacramento’s Pocket and Greenhaven neighborhoods. Barely 2 inches across, these mini dazzlers flit over lawns and streets in crazy zigzag patterns. (A couple got stuck on my Volkswagen’s grill.)

Were they migrating hundreds of miles like Painted Ladies or Monarchs? Did our summer heat cause a caterpillar explosion? Was this another sign of climate change?

No, most likely somebody just mowed a Yolo County field. And they’re not really yellow – they’re orange.

An Orange Sulphur butterfly rests on a sunchoke flower. (Photo:

Debbie Arrington)

Our colorful wave was a lot of displaced Orange Sulphur ( Colias eurytheme ) butterflies, according to UC Davis butterfly expert Dr. Art Shapiro, who had been contacted by more than one Pocket resident. “(It’s) a very abundant species that breeds on cultivated alfalfa as well as various wild legumes,” he said. “They disperse in all directions when the rancher cuts the alfalfa and then often show up in urban areas. I suspect the source is an alfalfa field across the river in Yolo County.”

After their home is mowed down, the butterflies go looking for more food – particularly clover lawns. Nicknamed “Alfalfa Butterfly,” the Orange Sulphur prefers flowers in the pea family – alfalfa, clover, vetch, lupine, etc. – but will feed on sunflowers and other members of the aster family as well as milkweed and other high-nectar flowers.

“They may (lay eggs) on clover in lawns but the larvae will not do any damage,” Shapiro said. “The first generation or two in spring breed(s) on annual vetches ( Vicia species). They switch to alfalfa when the vetch dries up.”

That erratic, bouncing, up-and-down flight pattern is a way to avoid getting eaten themselves. Predators have a hard time grabbing them in mid-flight.

When feeding on a flower, Orange Sulphur butterflies usually keep their wings together, displaying menacing little “eyes” on the undersides of their wings. (That’s another defense tactic.) While the underside has spots, the wings’ topside usually has black borders, but that can vary.

With enough food and warmth, this butterfly species can remain active year round, making it one of our most common butterflies, Shapiro said. “This is also our most variable butterfly, seasonally and individually.”

In winter, Orange Sulphurs are smaller with more subdued coloring. In summer, they’re bigger and brighter. Another twist, many females are more cream-colored than orange or yellow.

In early autumn, they’re most numerous – or appear that way – because that’s when alfalfa is often harvested.

“By the way, the very similar Colias lesbia does all the same things in Argentina,” Shapiro noted. “Dispersers from alfalfa in the Paraná Delta often show up in downtown Buenos Aires and visit flowers in window boxes on high-rise apartment buildings!”

For more on Orange Sulphur butterflies: https://butterfly.ucdavis.edu/butterfly/colias/eurytheme .

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milkweed Sacramento nectar plants asters fields native insects alfalfa gardening sunflowers autumn Orange Sulphur butterflies flowers peas

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Garden Checklist for week of May 5

Survey your garden after the May 4 rainstorm. Heavy rain and gusty winds can break the neck of large flowers such as roses. Also:

* Keep an eye on new transplants or seedlings; they could take a pounding from the rain.

* Watch out for powdery mildew. Warmth following moist conditions can cause this fungal disease to “bloom,” too. If you see a leaf that looks like it’s dusted with powdered sugar, snip it off.

* After the storm, start setting out tomato transplants, but wait on the peppers and eggplants (they want warmer nights). Pinch off any flowers on new transplants to make them concentrate on establishing roots instead of setting premature fruit.

* Trim dead flowers but not leaves from spring-flowering bulbs such as daffodils and tulips. Those leaves gather energy to create next year's flowers. Also, give the bulbs a fertilizer boost after bloom.

* Pinch chrysanthemums back to 12 inches for fall flowers. Cut old stems to the ground.

* Mulch around plants to conserve moisture and control weeds.

* From seed, plant beans, beets, cantaloupes, carrots, corn, cucumbers, melons, pumpkins, radishes and squash.

* Plant onion sets.

* In the flower garden, plant seeds for asters, cosmos, celosia, marigolds, salvia, sunflowers and zinnias. Transplant petunias, zinnias, geraniums and other summer bloomers.

* Plant perennials and dahlia tubers for summer bloom.

* Don’t wait; plant summer bulbs, such as gladiolus and tuberous begonias.

* Harvest cabbage, lettuce, peas and green onions.

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