Research Summary

Roadside Surveys
  • The majority of the milkweed (asperula) was found in the Edward's Plateau and Cross-timbers.
  • The lowest number of milkweed was in the South Texas Plains.
  • We are evaluating the relationship between abundance and precipitation.
Site-Specific Surveys
  • Compared to roadside locations, there is more milkweed in the site specific locations.
Seed Viability and Germination
  • Viability is not an issue.
  • Germination is not an issue for most milkweed species.
  • Most milkweed species have the photosynthetic characteristics of heliophytes.
Light Level Responses
  • Significant differences in transpiration rates were at the highest and lowest light intensities tested.
  • Significant differences in stomatal conductance were at the highest and lowest light intensities tested.
Patch Size
  • There is not an optimum spacing or density of milkweed for monarch reproductive success.
Nectar Density
  • Only under extremely high densities of nectar plants do you see increases in monarch success.
  • Tropical milkweed will increase monarch success in the spring.
Best Management Practices
  • Disturbance seems to increase the number of milkweed stems, but the effect is short-term.
Fire Ant Mounds
  • All larval stages of monarchs are preyed upon by red imported fire ants.


funding provided by    the Texas State Comptroller Office