Texan Magazine
By Marc Hess, Editor Gardening South Texas newsletter
The monarch population is declining. What would happen if monarch butterflies went extinct? Adult monarchs are vital pollinators. Many of the plants humans and other wildlife depend on (think fruits, vegetables and herbs) require pollinators to reproduce. The decline in monarch populations also indicates the health of other pollinator populations, which directly impacts human food systems.
How Can We Help
Monarchs migrate from north to south each year. We get to see a lot of them here in South Texas every September and October while they are taking a critical nectar break before the final leg of their migration to their wintering ground in forested mountains west of Mexico City where they roost on the fir trees until next March.
Monarchs funnel through Texas both in the fall and the spring. During the fall, monarchs use two principal flyways. One traverses Texas in a 300-mile-wide path stretching from Wichita Falls to Eagle Pass. Monarchs enter the Texas portion of this flyway during the last days of September. By early November, most have passed through into Mexico. The second flyway is situated along the Texas coast and lasts roughly from the third week of October to the middle of November. The total life span of this wintering generation of monarchs is approximately eight months from September through April.
On their return trip, monarchs begin arriving in Texas in March. On this north-bound leg of their journey they are seeking emerging milkweeds as they move through Texas laying eggs before dying. The Texas-born generation only lives about three weeks, just long enough to fly farther north to lay eggs on other milkweed plants. The offspring of this north-bound generation is also short lived but, as it leaves Texas behind, it moves farther north and eventually spreads over a wide range re-populating the eastern half of the United States and southern Canada.
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Texas is a critical state in the survival of monarchs.
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The complexity of the monarch’s life cycle and their dependence on the availability of milkweed and a diverse set of habitats make them vulnerable to population fluctuations. Removal of roosting trees, ecotourism in Mexico, cold weather, droughts, destruction of milkweed and insecticide use have contributed to a severe population drop since 2012. The Center for Biological Diversity estimates that, nationwide, monarchs have declined 85% in their population.
Overall, the migrating populations are thought to be less than half the size they need to be to avoid extinction. Texas gardeners, government entities and nonprofits have been responding to the challenge of monarch population stability. Texas universities are conducting research with donated and tax-supported funding and thousands of milkweeds have been planted.
The Texas Milkweed Controversy
Milkweeds (genus Asclepias) are the sole group of host plants for monarchs. It is the ONLY plant on which the butterfly will lay eggs, and the ONLY food source for monarch caterpillars. Monarchs cannot complete metamorphosis without milkweeds. That is why planting milkweeds is especially important in Texas.
Milkweeds are perennial plants, which have evolved in tandem with the Monarchs. Their bloom and dormancy patterns match the monarch migration. The local native Antelope Horn milkweed (A. asperula), for instance, grows quickly and blooms in the spring and fall, when the monarchs are passing though Texas, but it disappears entirely in the summer and winter, when the butterflies have gone north or south. Unfortunately, most native milkweed species have notoriously low rates of germination, so growing native milkweed from seed at home is quite difficult. It also lacks the bright colors that Texans like to see in their gardens.
The more colorful Tropical Milkweed (Asclepias curassavica) is the variety most Texas gardeners choose to put in their landscapes. It is native to South America and grows upright with orange, red, and yellow flowers. Monarchs will lay eggs and enjoy nectar from tropical milkweed. But the plant can pose a great danger to the butterflies. Because tropical milkweed is native to the Southern Hemisphere, it’s not synced to the seasons in North America. This species has a much longer flowering period than native species, and will tend to keep blooming until frost. This can confuse the butterflies into sticking around late into the fall. Late-blooming tropical milkweed delays the monarchs’ natural migration pattern, causing them to die from cold before they can reach Mexico.
The Solution
There is a very simple solution to this situation. Gardeners can cut their tropical milkweeds to the ground in October. However, most gardeners find no incentive in cutting back their plants when they are displaying their most attractive blooms.
A better, native alternative to tropical milkweed is Butterfly Weed, Asclepias tuberosa. Due to popular demand and growing concern about Monarchs, Asclepias tuberosa has become more available at nurseries in recent years. Because it looks similar to tropical milkweed, look for the plant by its Latin name, A. tuberosa, to make sure you are buying the correct species. Tuberosa is native to most of the continental US and will not interfere with the monarch’s migration.
Once safely in the butterfly stage, monarchs expand their diet. They eat nectar from a variety of plants enjoyed by other butterflies, including lantanas, mistflowers, and verbenas. Wildlife gardeners should also consider planting fall-blooming perennials to bolster the buffet of nectar-rich options for butterflies. These landscape plants put on their biggest bloom show in September and October, just as the monarchs are making their way south through our area.
WHITE MISTFLOWER is a small shrub that occurs locally in the wild and can also be found in nurseries.
GREGG’S MISTFLOWER is not only beautiful but irresistible to monarch and queen butterflies.
SHRUBBY BLUE MISTFLOWER, (aka Crucita), is the Rio Grande Valley mistflower, but it will reach into southern Bexar County and it’s irresistible to all butterflies.
SCARLET SAGE thrives in virtually all conditions, especially partial shade. Its cheerful red blooms feed butterflies and are also a favorite of hummingbirds.
MEALY BLUE SAGE is one the most common Salvias in our area and therefore a favorite butterfly food.
AUTUMN SAGE is a very common perennial in South Texas landscapes and it comes in red, purple, pink, and white varieties.
FROSTWEED is one of their favorite plant species. Found growing under the shade of live oaks, this plant’s blooms are timed perfectly for the fall migration. Gather seeds later this year and toss them in a shady spot in your yard.
PLATEAU GOLDENEYE puts on a show every autumn with an abundance of yellow blooms. After they finish blooming consider leaving them (their seeds) as a food source for songbirds in the winter. This plant is great for large areas as it will sprout readily from seed and form colonies.
TURK’S CAP is a native perennial that adapts to sun and shade. Many varieties exist, including pink flower ones to large flower tropical species.
