Moths and butterflies: Understanding their role and diversity in our gardens
By Penny Pawl
NAPA VALLEY, Calif. — I recently saw an image on a Facebook page devoted to owls that generated a lot of discussion. Some people thought the creature in the image was a butterfly; others were sure it was a moth. I decided it was a moth based on information I had found online. Some said it was an owl butterfly, and other commenters wondered if the image was generated by AI. It turns out the AI guess was right.
Did you know that both moths and butterflies are in the same family? The family name is Lepidoptera. Moth species outnumber butterfly species by about 9-to-1. Some moths fly during the day and others at night, while most butterflies like to fly and feed during the day. A small number of butterflies fly at day’s end. Moths are pollinators that feed in the garden mostly at night.
I occasionally find hornworm caterpillars on my tomatoes. Rather than kill them, I move them to open ground, put large containers over them and feed them tomato leaves. The caterpillars mature until they are ready to make a cocoon. At that point they dig or dive into the soil and stay there for two to three weeks, weaving a cocoon around themselves. Then they emerge as large brown moths with a wingspan of 5 inches.
The moth form of the tomato hornworm is known as the five-spotted hawkmoth (Manduca quinquemaculata). Their preferred nectar is from white flowers, especially white nicotiana, but they also feed on California fuchsia (Zauschneria californica) and manzanitas. The pupa overwinters in the ground and usually emerges in May. It remains a larva for about a month.
I have read that nicotiana has an odor at night that attracts the moths, but I have never seen a butterfly on my nicotiana plants.
The moth larvae are used by many birds to feed their babies each spring and summer. If you are interested in studying moths during the summer months (it’s too cold now), I suggest you read this article from the Good News Network on the beauty of moths. And celebrate National Moth Week this summer from July 20 to July 28.
Ecologists have deemed the monarch butterfly a keystone species. This designation means that the decline in the number of monarchs reflects what is happening to other butterflies. The population of monarchs overwintering in Mexico has dropped by millions. The population on the Pacific Coast is nowhere near what it was in years past.
The magazine Xerces is named after a small blue butterfly that once lived in San Francisco’s Golden Gate Park. The Xerces butterfly is now extinct, and we are to blame for its demise through urban development and habitat destruction. It was last seen in 1943.
It is important not to let other butterflies suffer this fate. What can home gardeners do to help prevent this from happening? We can plant nectar plants and other plants that butterfly and moth larvae use. Lawns do not yield nectar-producing flowers.
This year grow a few extra tomatoes so the hawk moth can have a food source. Plant native milkweed, which is a host plant for monarch butterflies. They lay their eggs on its leaves and the caterpillars eat the leaves. Grow a variety of nectar-producing plants to feed pollinators. Not only will the butterflies and moths thank you, but hummingbirds and bees will, too.
All of these creatures are drawn to large patches of flowers, so don’t just plant one or two. More is better. And they like a diverse combination of native plants. Native plants evolved with native insects and birds.
According to Xerces magazine, oak trees support more varieties of moth larvae than any other type of plant. The Fall 2023 issue of Xerces is devoted to moths, so you might try to find this issue of the publication if you would like more information.
Library Talk: UC Master Gardeners of Napa County and Napa Library will host a talk on Thursday, March 7, on “Agaves — More Than Tequila and Century Plants” from 7 to 8 p.m. via Zoom. Learn more about adding these deer-proof, beautiful and low-maintenance plants to your garden. Register here to receive the free Zoom link.
Workshop: Join UC Master Gardeners of Napa County for “Spring Into Summer Vegetable Garden” on Saturday, March 9, from 8 a.m. to 5 p.m. Plan your vegetable growing for the warm weather ahead. Topics include soil prep, fertilizing, managing pests, irrigation and planting schedules. This is a hands-on workshop and registration is required.
Help Desk: The Master Gardener Help Desk is available to answer your garden questions on Mondays and Fridays from 10 a.m. until 1 p.m. at the University of California Cooperative Extension Office, 1710 Soscol Ave., Suite 4, Napa. Or send your questions to mastergardeners@countyofnapa.org. Include your name, address, phone number and a brief description. For best results attach a photo.
If today's story captured your interest, explore these related articles:
Penny Pawl is a UC Master Gardener of Napa County.
Very interesting Penny. I like your idea about the tomato hornworms. I hate to kill things!!
I don’t think people realize that it literally takes the whole village (or as my Mexican friend says, ‘All the beans in my burrito’) working together to feed everyone. It’s like we’re are own mini World Central Kitchen. I could send photos of the greenhouses already planted.