Monarch Butterflies Visit San Antonio Each Year!

By Monika Maeckle

Monarch butterflies now leave their roosts in the Oyamel forest of Michoacán, Mexico generally late March — their latest departure on record, according to citizen science organization Journey North. And they start showing up in San Antonio, laying their first generation of eggs on local milkweeds.

Because of Texas’ unique position in the geographic path of the Monarch butterfly migration — the first stop in the spring and the “funnel” to Mexico in the fall — the Lone Star State has been called the most important state to the iconic butterfly migration.

Monarch caterpillar on milkweed plant.

They make initial migratory stops in South Texas to lay the first generation of eggs in the multi-generation migration exclusively on Asclepias species, or milkweed. Although milkweeds are late, they are sprouting up in San Antonio area gardens, so the butterflies will enjoy sustenance for their offspring when their eggs hatch into caterpillars in the coming weeks.

The challenge is that it’s almost impossible to find native milkweeds in commercial nurseries. Only non-native tropical milkweed, Asclepias curassavica, is widely available along with occasional butterflyweed, Asclepias tuberosa.

Another challenge is that commercial growers often spray milkweeds with systemic pesticides that poison Monarch caterpillars when they eat the plant’s leaves.

Clean, chemical-free, native milkweeds are in great demand and hard to find. So if and when you buy milkweeds, always ask and make sure it has never been sprayed. As a safeguard, I planted and overwintered the reliable tropical milkweed after slashing them to the ground in December as recommended.

Detractors have their concerns, but I’m a huge fan of tropical milkweed and provide the host plant in my downtown San Antonio garden. The leaves are lush and ready for Monarchs.

Monika Maeckle is a member of the Community Conservation Committee and authors the Texas Butterfly Ranch, a pollinator and native plant advocacy blog.

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