Plight of the Monarchs

By William Scheick, Contributing Editor

For some people, a controversy seemed to start with an e-mail message from a plant nursery located near Austin.

The message began with “It’s butterfly migration season! … KILL YOUR MILKWEED NOW!” The exclamation points and the capital letters implied urgency about eradicating all garden milkweed. Several of its readers, however, were more than surprised. They were alarmed by the message, which they believed was worse than merely bad advice.

Actually, this plant-nursery prompt was hardly the beginning of a butterfly/milkweed controversy. As a spokesperson at the nursery later replied to her critics, “This information is what the monarch experts are telling us.”

Obviously, while many of us have simply been enjoying the beauty and value of milkweed in our gardens, there has been a debate going on behind our backs about whether we are helping or hurting monarch butterflies (Danaus plexippus).

What's the problem?

Before we consider this debate, it helps to understand the problem that has led to it.

That problem is the precipitous decline in the population of monarchs — a plight so dramatic that the U.S. Fish and Wildlife Service is currently considering whether these butterflies should be classified as an endangered species.

The number of them overwintering in Mexico has been declining rapidly during the last 10 years. By the end of 2014, their south-of-the- border presence amounted to about 10 percent of the monarchs’ average total there during the last 20 years.

The monarchs making their way to Mexico are not round-trippers. They are multi-generational descendents of butterflies that left Mexico during early spring to mate and then deposit eggs on aphid-free milkweed foliage growing in Texas and other places farther north.

These monarchs died at some point in this journey, but their eggs (left variously along the way) produced caterpillars that chomped milkweed leaves until these crawly critters became chrysalises.

Emerging from this pupal stage, new butterflies continued the species flight northward, repeating a birth-death-birth cycle until some got as far as Canada. Eventually these surviving monarchs (sometimes surfing behind cold fronts) undertake a collective return to the oyamel fir trees of Mexico.

Theirs is a dicey venture. So much can go so wrong so easily. Record-breaking heat and drought in Texas are just two (among other) natural impediments to their migrations, both leaving and returning.

Desiccation threatens eggs, pupas and adults as well as inhibits the sprouting and resilience of various milkweed species, the only plants monarchs require during reproduction.

Monarch caterpillars emerge and then feed exclusively on milkweed, whereas the winged adults drink nectar from and pollinate a wide assortment of wildflowers. The adults, however, remain as predator-protected as the caterpillars by the bitter and toxic chemicals (cardenolides) that they acquire from butterfly weed.

Milkweeds native to North America have become less abundant at the same time as monarch populations have dwindled. Given their critical inter-species relationship, it is not surprising that the loss of wild milkweed plants has coincided with the loss of monarchs.

The reasons for milkweed’s decline remain under study, although substantial habitat loss through human intervention is a major factor.

But for gardeners — especially given the important Texas-stage in the monarch’s flight northward and return southward — the key question might be, “What can we plant to help?”

A popular host

At garden centers, the most available milkweed is tropical butterfly weed (Asclepias curassavica), a gorgeous Mexican and Central American native. Indian or bloodroot, as it is also known, has been a prized garden plant for a long time and has naturalized in Texas and elsewhere.

Monarchs love this plant as much as gardeners and so (understandably) some butterfly experts and breeders have celebrated tropical milkweed as a bonanza for these butterflies.

That’s the case for Dale Clark, president of the Dallas County Lepidopterists’ Society, who has maintained that Mexican butterfly weed is a boon to the monarchs, especially during the harsh environmental conditions Texans have experienced in recent years.

His webpage for Butterflies Unlimited, which he runs in Glenn Heights, TX, features a monarch nectaring on tropical milkweed, a plant that butterfly breeders acclaim to be especially ideal for collecting monarch eggs.

Geyata Ajilvsgi, in her comprehensive Butterfly Gardening in Texas, likewise views this plant as an “especially good nectar producer as well as a favored larval food plant” for monarchs.

A popular beautiful flower for a popular beautiful butterfly would seem to be a win-win, right? Maybe not.

In 2015, the Royal Society published a report that drew little attention until its findings were summarized in Science, the prestigious journal of the American Association for the Advancement of Science.

The Science essay was provocatively titled “Plan to Save Monarch Butterflies Backfires,” which of course caught the attention of newspaper reporters.

The news stories that followed sometimes gave the impression that milkweed in our gardens resulted in more harm than good for monarchs.

This was certainly not what the researchers had actually concluded, but rumored misinformation spreads fast and often dies hard. It likely infected that nursery e-mail proclaiming, “KILL YOUR MILKWEED NOW!”

What the research really says

The alleged problematic milkweed, according to the research report, is specifically the popular Mexican butterfly weed.

Tropical milkweed, the study concluded, possibly delays the monarchs’ return flight to Mexico. This outcome occurs primarily in the Deep South but possibly anywhere else Indian root does not die back during the monarchs’ return journey.

Usually, according to the researchers, autumnal monarchs on their way to Mexico would encounter seasonally diminished native milkweeds. Theoretically, these less appealing plants incentivize the butterflies to keep moving southward.

Where winters are warm, however, tropical milkweed can grow new foliage and flowers. Wherever this plant does not seasonably die back, the researchers speculate, monarchs tend to linger, postponing their passage and also engaging in more reproduction than is normal during that time.

And then something awful happens.

According to the researchers, “diminished migration increases infection risk” by a parasite known as Ophryocystis elektroscirrha (OE). Whereas OE is naturally checked by plant dieback, it seems to accumulate at atypically high levels on the foliage of year-round tropical milkweed. Such increased OE spore loads threaten the health of lingering monarchs.

The lingerers are not the only monarchs affected. The parasites’ spores spread from afflicted butterflies to their mates. These amassing spores also contaminate the foliage and flowers of bloodroots that do not die back, which then afflict future nectarers and larvae. As a result, adult monarchs and their offspring become impaired, both no longer capable of a normal life span.

The debate

Although these findings were only provisional and appeared in a working paper (research in progress), they quickly became controversial.

Much of the debate, obviously, resulted from the mistaken impression that the study presented finalized research and applied to all garden milkweeds. Native-plant enthusiasts quickly tried to emphasize the difference between native milkweed species and Mexican bloodroot.

Yet even when the debate focused on tropical milkweed, there were reservations expressed by some people devoted to monarch propagation — people keenly aware of the toll of pesticides, herbicides and ongoing climatic challenges on all pollinators, including bees.

They wondered whether this single plant species, however popular, could make such a big difference in monarch populations. After all, the reported impact was restricted only to relatively small geographical areas where that plant did not seasonally die back soon enough or at all.

And, skeptics also asked, what about the native milkweeds that (during favorable conditions) have not seasonally degraded and (in some instances) are even blooming again during the monarch’s return flight? Aren’t they implicated, too? Were there other possible explanations for increased monarch winter-breeding in the southern U.S. — such as our hotter hardiness zones?

And, some questioned, do we actually know whether our warmer Southern conditions are a minus rather than a plus for future monarchs, whose ancestral habitat in Mexico is disappearing?

The options

Refereeing this debate is beyond my expertise. All I have are some personal thoughts, which will not please everyone but which I offer here for whatever they might be worth.

First, I suspect that there is no pressing need to cut back native butterfly weed in our gardens during fall and winter, even if our augmented microclimates and watering keep them performing better than if they were growing wild. By autumn the foliage of this plant is usually not very appealing to monarchs.

On the other hand, I equally suspect that there would be no harm to monarchs in cutting back gardened native milkweeds in mid-autumn, if you prefer. Cutting them back will not harm returning monarchs nor will it kill these taprooted perennials.

Second, deciding for or against tropical milkweed remains a hard call. Lacking a taproot, Mexican butterfly weed tends to die (like an annual) during winter in most of Texas. In favorable settings it can seed, which is why it has naturalized in parts of our state. Caution, then, might suggest at least cutting it back in October.

But should tropical milkweed be eliminated altogether from gardens, as some have advocated? Are we “morally and ethically unfit to garden” if we grow it?

At present we lack conclusive data about the impact of this plant on monarchs. Statistics for San Antonio, for example, apparently show very little additional OE on longer-term tropical milkweed.

There is evidence, reported by various butterfly experts, that tropical milkweed can contribute to monarch survival during spring and maybe autumn, too.

In an issue of American Butterflies, biologist Jeffrey Glassberg (president of the North American Butterfly Association) wrote: “There is good reason to think that tropical milkweeds might increase the number of monarchs and may become critical life-buoys, protecting migratory monarchs from the projected loss of their overwintering grounds in Mexico.”

Or, as an anonymous monarch breeder likewise pointed out, “if faced with the question of letting a caterpillar starve due to lack of a native milkweed, offer whatever can be used to save that life.”

Third, it is noteworthy that this same breeder also advised, “Please plant the best milkweed you can for the monarchs and actively protect our environment.”

That advice would surely encourage us to garden with native butterfly weed species. Planting these milkweed perennials in our gardens could make a difference in the plight of the monarchs and reduce the need to rely on controversial tropical butterfly weed as “critical life-buoys.”

Planting the perennials

After their taproots (which can reach two feet) are deeply established in draining soil, many native milkweed species can tough out drought, endure our intense sunlight and flower in large attractive clusters — features that should make these plants appealing choices for Texas gardeners.

Keep in mind, of course, that the very same bitter milkweed chemicals that protect monarchs from predation can cause skin rashes and also be dangerous if ingested by farm animals, pets or children.

Native milkweed species recommended for Texas gardens devoted to monarch support include butterfly weed (Asclepias tuberosa), Texas milkweed (A. texana), longhorn milkweed (A. oenotheroides) and showy milkweed (A. speciosa). For clay soils in our state, try antelope- horn milkweed (A. asperula) and green milkweed (A. viridis).

Seeding success

Milkweed seed has a reputation for being challenging. When I mentioned this to Emily Neiman (Native American Seed Farm in Junction, TX), she replied, “Germinating milkweeds is in no way hard. You just have to understand that the seeds need a cold, wet winter; and this can be mimicked by using your refrigerator.”

The webpage for her farm recommends submerging milkweed seeds in chilled, distilled water inside a sterilized container. Twenty-four hours later, the seeds should be strained and rinsed with distilled water to wash away any remaining germination-inhibiting chemicals.

Next, these seeds should be hand-mixed — sterile gloves required — with pre-moistened vermiculite. The mixture should then be sealed in a sterile container and refrigerated at 35–45. F. Between 30 and 45 days later, the seeds can be planted less than an inch into the ground when the outdoor temperature reaches at least 70. F. Bright sunlight will stimulate sprouting.

Seed for six different species of native milkweed is available from the Native American Seed Farm, where George Cates has cultivated about 600,000 milkweeds.

The Farm also offers a “Sustain the Migration Kit” and sells seed for several returning monarch nectar sources, including cowpen daisy and frostweed.

The need for nectar

Keep in mind, too, that adult monarchs need plenty of nectar, and not just from milkweed flowers.

They feast widely on spring wildflowers, while autumn blooms especially fuel their flight back to Mexico. Photos show monarchs visiting sunflowers, mistflowers, coneflowers, ironweeds, goldenrods, gayfeathers and cowpen daisies, among many others.

Texas Parks and Wildlife participates in joint national efforts to increase native habitats that sustain monarchs. So does the Native Plant Society of Texas, which plans to install “monarch waystations” at TxDot highway rest stops in Hill and Bell counties.

Every October, too, Wildseed Farms in Fredericksburg holds an annual Monarch Butterfly Celebration, when tagged butterflies are released from its gardens.

Bush on butterflies 

Speaking for the Texan by Nature organization, former First Lady Laura Bush said, “In order for Texas to remain a thriving central flyway for the Monarch butterfly, we must join together to conserve and create essential monarch habitat.

"Conservation truly begins at home," she said, "and with more Texans lending their time, expertise, land and resources, we can ensure that the Monarch butterfly — the state insect of Texas — is here to stay.”