Growing Spider Milkweed Seed for Monarch Butterfly

Reader Contribution by Terroir Seeds
Published on April 14, 2014

The collaborative efforts of Terroir Seeds, The Xerces Society and Painted Lady Vineyard have spent the past 2 years growing southwest native milkweed seed to reintroduce the Spider or Antelope Horns milkweed (Asclepias asperula) to home gardeners, garden centers and native plant nurseries across the southwest. This story is especially poignant right now with the massive declines in Monarch butterfly populations and the resounding recovery push by several conservation groups alongside private citizens, students and scientists.

Milkweed is Critical for Monarchs

The milkweed plant plays a critical role in the monarch life cycle. Each spring Monarchs migrate across the United States, laying eggs on native milkweeds – the only food plants suitable for newly hatched monarch caterpillars. The North American Monarch Conservation Plan recommends planting native milkweed species to restore habitat within the Monarch butterfly’s breeding range. 

For the past 3 years, the total area occupied by overwintering Monarchs in Mexico has dropped by almost 50% each year, continuing a decline that has lasted for the past decade. The severe drought seen across Texas and Northern Mexico has been a large factor, combined with wildfires across the entire southwest. The biggest contributor is simply the loss of land that supports the Monarch’s food source and hatchery – the Milkweed plant. Much of the land has been converted to commercial herbicide tolerant corn and soybean production or developed into housing. Overuse of persistent chemical herbicides and roadside mowing for weed control has also created loss of milkweed habitat and thus reduced Monarch numbers. 

Producing Milkweed Seed

The Xerces Society is working to increase the availability of native milkweed seed and encourage restoration using milkweed in California, the Great Basin, the Southwest, Texas, and Florida. These are important areas of the Monarch’s spring and summer breeding range where few commercial sources of native milkweed seed currently exist. Brianna Borders, Plant Ecologist, contacted us about growing out a small sample of Spider or Antelope milkweed seeds that had been collected in central Arizona to make it commercially available.

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