For Delmarva gardeners, the most consequential monarch decision may be which milkweed to plant — and whether it is native to the region. Milkweed supports monarch caterpillars, while nectar-producing flowers help adult butterflies refuel during migration. But experts say the wrong plant choice can create problems for monarch health and migration.
As reported by WTOP News, Lesley Ries, an associate professor in Georgetown University's biology department, has spoken about the appeal of watching monarchs up close during this stretch of their life cycle. Monarch butterfly kits, which let people watch caterpillars metamorphose into butterflies, remain popular for that reason. Ries has said the value of experiencing that transformation firsthand can shape lifelong support for conservation.
Why Milkweed Matters — and Why the Wrong Kind Backfires
Milkweed is not optional for monarchs. It is the required host plant for their caterpillars, and its flowers also provide nectar for pollinators more broadly, according to the Xerces Society. Monarchs feed almost exclusively on milkweed species within the genus Asclepias, per research published in the journal Ecology and cited by esajournals.onlinelibrary.wiley.com. The plant contains distasteful chemicals that monarchs eat and then sequester as their own defense — cardenolides that make the butterflies unpalatable to insect-eating birds, the same research notes.
But not all milkweed is created equal. Nonnative varieties, including tropical milkweed, can increase pathogen loads on the plant itself and raise disease risk in migrating monarch populations. The Xerces Society recommends planting milkweed species that are locally native, sourced regionally, rather than reaching for whatever is available at a nursery. If locally native milkweed isn't an option, the group suggests native wildflowers instead, since those still provide nectar for adult monarchs without the same risks.
What Recent Monitoring Shows
The latest overwintering estimate offers some short-term encouragement but does not erase the population's longer-term vulnerability. According to the Monarch Joint Venture, eastern monarchs occupied 2.93 hectares of Mexico's oyamel fir forests during the 2025-2026 season, about 64% more than the previous year's 1.79 hectares. Researchers have recommended at least six hectares of occupied overwintering habitat to sustain a resilient eastern population and migration, and recent estimates remain below that target, the organization says.
Coastal monitoring provides another way to track the migration beyond backyard sightings. The Coastal Virginia Wildlife Observatory says its Monarch Butterfly Migration Program has conducted fall surveys and tagged monarchs since 1998; some tagged butterflies were later found at winter roosts near Mexico City.
The Tropical Milkweed Problem
The trouble with tropical milkweed is that, in warmer climates, it can grow year-round instead of dying back in winter. That prolongs monarch breeding and lets disease spores build up on leaves across generations, according to Monarch Joint Venture. A 2015 finding cited by the group showed monarchs breeding on tropical milkweed throughout the winter carried higher levels of a protozoan parasite known as OE than monarchs following the normal migratory cycle. Tropical milkweed doesn't cure that infection, though it can cut disease severity roughly in half in monarchs that are already infected, the organization notes.
That's why researchers point toward native species instead — natives simply don't enable the same winter-breeding pattern that tropical milkweed can. The group also acknowledges some uncertainty about scale: could tropical milkweed's spread lead to more fall and winter breeding and more disease? Probably, per the same account, though it remains unclear whether winter breeding is becoming more common in the southern U.S. or what its population-level impacts might be.
Illinois offers a useful contrast. In that state, tropical milkweed dies back in winter, which lowers the odds it becomes a perennial source of pathogens or a magnet for nonmigratory monarchs, according to University of Illinois Extension. Even so, the extension warns that a longer bloom season from late-season tropical milkweed has been shown to disrupt reproduction and migration by encouraging adults to keep breeding instead of heading south. Separately, warmer temperatures have been found to raise cardenolide concentrations in tropical milkweed, a shift that researchers say may turn the plant from beneficial to detrimental for monarchs as conditions heat up, per the Ecology study.
What Local Gardeners Can Plant
WTOP's report names several milkweed varieties available in the region: common milkweed, swamp milkweed and butterfly weed. Seaside goldenrod, described as easy to grow, is also flagged as a benefit for monarchs along the Chesapeake. Fall is generally a good time to plant, since cold, moist winter and spring conditions can help stimulate germination, the Xerces Society notes — though newly planted milkweed may not flower or set seed in its first year, even if monarchs still use it to lay eggs.
The stakes behind these planting choices are real. The eastern North American monarch population has declined by roughly 90% since the 1990s, according to a 2015 report from Mongabay. Against that backdrop, breeding monarchs on a large scale — such as through commercial kits — raises the risk of disease spreading into wild populations, which is why the Xerces Society for Invertebrate Conservation advises against raising monarchs outside of education and research settings. Still, per the WTOP report, allowing children to collect and release monarchs can support long-term conservation attitudes, echoing Ries's point about the lasting impact of watching the transformation firsthand.
Where to See Monarchs Locally
Maryland's Wildlife and Heritage Agency, part of the state's Department of Natural Resources, has also weighed in on the issue; the agency's Max Ferlauto is identified in WTOP's reporting as a state etymologist there. According to the same report, the region has several events built around the migration this season: Monarch Tagging and Pollinators at Rollins Ford Park in Prince William County, the Monarchs and Milkweed Festival at Merkle Natural Resources Management Area in Upper Marlboro, Maryland, and Monarch Tag and Tea at Hidden Oaks Nature Center in Fairfax County.
For now, the monarchs making their way along the Delmarva coast are simply trying to fuel up before continuing thousands of miles toward their wintering grounds. What locals plant in their yards this fall — native milkweed and wildflowers rather than tropical varieties — may play a small but real part in whether that journey gets easier or harder for the generations of butterflies that follow.
