How far could you travel without your GPS before getting lost? For most of us, a long road trip is impossible without satellite assist. Monarchs have managed for millennia to navigate their way across the continent, drawn by an unseen force to migrate en masse. Each fall, nearly 500,000 monarch butterflies fly south to their wintering grounds in Mexico, completing the longest repeat migration in the insect world. Monarchs from the eastern United States make this long and dangerous journey, traveling from as far away as southern Canada, down through Texas, settling in mountains northwest of Mexico City – all without a map!
Unfortunately, eastern monarchs are in trouble; their population has plummeted nearly 90% over the last few decades and they need your help. Here are three easy ways you can make a difference:
1 – Cut back tropical milkweed
Tropical milkweed is a popular choice for many gardeners. This Mexican native adapts well to our region as it is easy to grow with a long bloom season. However, despite its role as an effective host plant for monarchs, this variety comes with concerns.
Given its ability to grow year-round, tropical milkweed interferes with monarch migration by inviting butterflies to linger instead of continuing on to their southern wintering grounds. If butterflies delay travel plans for too long they run into temperatures too cold to survive.
Biologists also believe tropical milkweed proliferates the spread of the ophryocystis elektroscirrha (OE) pathogen. OE is a protozoan parasite that monarchs carry and spread to their host plants. It’s then ingested when caterpillars feed on the leaves. According to the Xerces Society, high OE levels in adult monarchs have been linked to lower migration success in the eastern monarch population, as well as reductions in body mass, lifespan, mating success, and flight ability. When native milkweeds die back after blooming, the parasite dies along with them so that each summer’s monarch population feeds on fresh, parasite-free foliage. In contrast, tropical milkweed that remains evergreen through winter allows for OE levels to build up on the plant over time, meaning successive generations of monarch caterpillars feeding on the plant can be exposed to dangerous levels of OE.
If you grow tropical milkweed be sure to cut it back in the fall, preferably by early October. Leave the stalk 4-6 inches tall and keep cutting it back through February as leaves re-sprout.
2 – Plant natives for spring
If you don’t have milkweed in your garden, tropical or native, plant now for spring. Planting in the fall allows natives to establish a strong root system over winter, creating a more drought tolerant and healthier plant for monarchs and other pollinators to visit the following year.
Interested in planting milkweed? Try one of these native varieties. Milkweed is notoriously challenging to propagate so follow planting guidelines closely. Many local gardeners report good success with the aquatic (Asclepias perennis) and swamp (Asclepias incarnata) varieties.
Milkweed is the only plant that monarchs will lay eggs on and the only food source for their caterpillars. Monarch caterpillars are voracious eaters, capable of consuming an entire plant as they grow. To ensure an adequate food supply throughout their larval stage, bunch at least 4-5 plants close together.
In addition to milkweed, native nectar-rich plants are a much-needed food source for adult monarchs. Monarchs will travel back through Texas in March and April, looking for nutrients along the way. Give them a hand by adding some of these native plants to your garden this fall.
3 – Avoid pesticides
Be aware that insecticides and herbicides are harmful to not only the target pest but pollinators and other beneficial insects, as well. You don’t have to spray a butterfly directly to harm it: plants absorb these chemicals, toxifying their leaves and nectar and poisoning visitors. Help protect monarchs and other pollinators by avoiding chemicals in your landscape. Look here for organic alternatives.
Begin with one easy change to help countless monarchs this fall. If you were traveling 3,000 miles, wouldn’t you appreciate a little help?