... Bee balm, goldenrod, black-eyed Susan and thistle would help, too.

Milkweed is the plant that monarch caterpillars need to eat, and the others are food sources for the butterflies.

This is important because, as expected, the overwintering population of the monarch butterfly in Mexico has dropped to its lowest level since record-keeping began in 1993.

This winter, the black-and-orange butterflies cover only 1.65 acres in the pine and fir forests west of Mexico City. That compares with 2.93 acres last year and more than 44.5 acres at their recorded peak in 1996, according to a report by the World Wildlife Fund.

The decline is blamed on several factors, including urban sprawl in the United States, extreme weather trends and the dramatic reduction of the butterflies' habitat in Mexico due to illegal logging of the trees they depend upon for shelter.

But one of the biggest reasons for their decline can be found right here in Iowa and Illinois. Common milkweeds — the principal food of monarch caterpillars — are killed when farmers apply the herbicide Roundup to their corn and bean fields.

The reason the corn and beans don't die is because they are "Roundup-ready," or genetically modified to resist the herbicide. Of course, farmers have been trying to eliminate milkweed forever. Previously, this was done by tilling the soil between the crop rows with an implement called a cultivator.

But chemicals are more of a sure thing.

Studies forwarded to me by Dr. Donald Lewis, an entomologist at Iowa State University in Ames, say there has been a "58 percent decline in milkweeds on the Midwest landscape, with an 81 percent decline in monarch production in the Midwest from 1999 to 2010." This is "coincident with" the use of Roundup, the studies say.

Another reason for a reduction in milkweed is that more acreage has been tilled and planted to row crops in recent years. Chip Taylor, the founder of Monarch Watch at the University of Kansas, attributes that to the ethanol mandate.

"Corn planting has been increasing ever since (the passage of the Clean Energy Act of 2007), with the result that farmers have removed hedgerows and narrowed field margins," he says. "In much of the Corn Belt, farming is from road to road, with little habitat for any form of wildlife remaining."

People who study monarchs say the butterflies are not in danger of extinction. Populations live elsewhere and some will survive. (Hopefully.) But their numbers will be severely reduced, and the so-awesome-we-don't-even-realize-it migration may end.

WHAT WE CAN DO: Regular gardeners like you and me can help by planting the native plants the butterflies need.

If every urban yard had just a little patch of native plants, the sum total would make a difference, says Dr. Douglas Tallamy, a professor of entomology at the University of Delaware who has been on the forefront of promoting backyard habitats.

Right now, the Scott County Soil and Water Conversation District is selling 13 different kinds of wildflowers, including the butterfly milkweed, a beautiful deep-orange blooming plant. Orders will be accepted through March 21, with delivery in late May. For more information, call Jan at 563-391-1403, Ext. 3.

Another step gardeners can take is to eliminate the use of synthetic insecticides.

OTHER INSECTS NEED HELP, TOO: In a Nov. 22, 2013, news analysis in the New York Times, Tallamy poses a thought-provoking question.

Although "we notice the (decline of) monarchs and bees because they are iconic insects, what do you think is happening to everything else?"

Most of us never think about insects except when they bother us: Mosquitoes, Japanese beetles and emerald ash borer immediately come to mind. But there are far more insects that are beneficial than harmful. And necessary to our survival, even.

Insects help stitch together the web of life with essential services. They break down plants into organic matter, serve as food for birds and, critically, pollinate our food crops. Sterility reduces insect life, which is no small matter.

Scott County Master Gardener Dan Mays (the voice in today's centerpiece story) tells me that Iowa recently has become a hotbed of insect enthusiasm.

For the past several years, Reiman Gardens at ISU has hosted a "Day of Insects," which invites insect enthusiasts of all persuasions (professional, academic, amateur and novice) to gather and share information.

"The format is to have a lot of speakers give lots of short presentations on a wide range of topics in 15-minute bursts," he said. 

This year's event will be March 29. There's an emphasis on butterflies and insects native to Iowa, but exotic and endangered insects, and conservation efforts, also will be covered.

If you are interested, go online to reimangardens.com/collections/insects/day-of-insects.

IN DEFENSE OF WINTER: "Worst winter in memory" was the headline on the front page of Tuesday's Quad-City Times.

I would say that because winter is a season of snow and cold, this is one of the BEST winters in memory. (I'm still partial to the winter of 1978-79. Colder, and more snow at once.)

To me it has been calming. The mild winters we've had recently — particularly that bizarrely hot March of two years ago — made me anxious. It was as though Earth was rubbing my nose in global warming.

This year has been the way it should be. I don't want to live in a world where snow exists only in memory.