Milkweed Must-haves for Monarchs

Cleveland Powell

Twice a year, South Texas becomes Butterfly Alley as millions of migrating monarchs flutter by. Plant native milkweed to give Momma Monarch a welcoming way station to lay her eggs.

Monarch butterflies are the only species of butterfly that make a two-way cross-continent migration. Monarch larva can only eat milkweed, plants in the genus Asclepias, and the most plentiful fields of milkweed are found in the Midwest.

While other butterflies shelter the cold in place either as larva or pupa, monarchs can’t withstand the cold so every fall, they fly from as far north as Canada to the oyamel fir forest in Mexico to escape freezing temperatures. The path most monarchs take leads them directly over Texas.

You can be a part of one of the most majestic and awe-inspiring events in the natural world by making a few simple changes to your landscape this fall. Planting milkweed species in your own landscape this year will ensure mother monarchs flying in from Mexico next spring will have plenty of plants to lay their eggs on. Luckily, there are a number of milkweed species that occur naturally in the San Antonio area.

The most common milkweed I see growing wild, along roads, parks and in the lawns of unsuspecting homeowners is zizotes milkweed (Asclepias oenotheroides). It can be found growing in the deep soils along the Mission Reach of the San Antonio River and the thin soils of northern Bexar County. Zizotes produces bountiful foliage for voracious monarch caterpillars.

The flowers are small but intricate and will appear periodically from spring until fall, whenever the plant receives adequate moisture. It’s the zizotes plant that I visit when I want to find monarch eggs to raise to adults.

In the Hill Country proper, antelope horn milkweed (Asclepias asperula) is a common sight along farm roads. It does great in low soil situations, and in extreme cases I’ve seen it growing out of limestone cracks and caliche. In the spring — and fall if the weather is right — large umbels of flowers will attract your attention and a multitude of pollinators. As the seed pods grow and begin to ripen, they take on a distinct curve said to resemble antelope horns. Similar in appearance to antelope horn, green milkweed (Asclepias viridis) is a more robust milkweed great for deeper soil.

While most milkweeds won’t do well in full shade, Texas milkweed (Asclepias texana) is an exception to the rule. Adorned with delicate bright white flowers, this Hill County endemic is a great plant to include in any shady flower bed. It also looks great in sun!

Butterfly milkweed (Asclepias tuberosa) is the most striking native milkweed. Its bright orange flowers are sure to please both your human and pollinator friends. Another bonus: it’s one of the easier milkweeds to find in the nursery trade.

One of the more unique looking milkweeds of our area is wand milkweed (Asclepias viridiflora). It produces one or two zig-zaggy stems up to 3 feet tall, said to resemble magic wands. The large clusters of green and purple flowers are sure to catch the eye.

While not naturally occurring in our region, tropical milkweed (Asclepias curassavica) is also a species of milkweed monarchs will lay their eggs on. But this milkweed is not recommended for central Texas and has been known to promote disease and parasite infestation.

While monarch larva are the most conspicuous users of milkweed, there are a host of other insects that make use of various parts of the plant. The flowers are magnets for pollinators large and small. The leaves are eaten by the longhorn milkweed beetle, queen butterfly caterpillars and milkweed tussock moth caterpillars. Black and orange milkweed bugs are a common sight on plants with developing seed pods. Each milkweed plant is a tiny ecosystem, providing habitat for herbivores, predators and nectar feeding insects.

Many people consider milkweed hard to grow, but if you can learn their quirks milkweeds require little to no maintenance. Milkweeds tend shed their leaves when installed in landscapes. Don’t fret, the plant is just recouping and will re-sprout when the time is right. I’ve seen plants stay dormant for a whole year after planting.

Also, they tend to lose their leaves throughout the year. Again, the plant will come back when the timing is right. Avoid over-watering native milkweeds, they’re all adapted to the climate of South Texas and tend to do better with neglect rather than pampering.

Each mature plant will produce several seed pods a year. Collect the seeds to share with friends or let them fly free to spread naturally!

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