Roadside Surveys of Milkweed Species


Texas map

Four cross-Texas transect roadside surveys (Pineland to Ozona, Wichita Falls to Alice, San Antonio to Laredo, and Del Rio to Alice) were conducted during spring and fall of 2016, 2017, and 2018.

Every 10 miles:

  • 750 m2 were sampled and the following was measured:
    • Number and species of milkweeds
    • Percent cover of other species
    • Number of flower blooms
    • Distance to the nearest fire ant mound
    • Cover of soil, rock, and litter
    • Number of monarch eggs and larvae
  • 50, 1m spaced line-point and percent cover measured
Asclepias asperula
milkweed
Asclepias emoryi
milkweed
Asclepias latifolia
milkweed
Asclepias linearis
milkweed
Asclepias oenotheroides
milkweed
Asclepias verticillota
milkweed
Asclepias viridiflora
milkweed
Asclepias viridis
milkweed

Spring Average (2017-2018)

milkweed species

total stems found

# of sites where present

mean stem density when present ± SE
stems/m2

A. asperula

270 ± 428

23 ± 0

0.091 ± 0.042

A. emoryi

6 ± 6

1 ± 0

0.002 ± 0.002

A. latifolia

3 ± 3

1 ± 0

0.001 ± 0.001

A. linearis

3 ± 3

1 ± 0

0.002 ± 0.002

A. oenotheroides

64 ± 43

9 ± 0

0.008 ± 0.002

A. viridiflora

23 ± 17

3 ± 0

0.007 ± 0.005

A. virdis

291 ± 50

13 ± 0

0.027 ± 0.004

map

Fall Average (2016-2017)

milkweed species

total stems found

# of sites where present

mean stem density when present ± SE
stems/m2

A. asperula

216 ± 38

16 ± 38

0.018 ± 0.004

A. emoryi

4 ± 2

2 ± 38

0.002 ± 0.002

A. latifolia

1 ± 1

-

0.001 ± 0.001

A. oenotheroides

23 ± 10

6 ± 38

0.007 ± 0.001

A. verticillota

2 ± 1

1 ± 38

0.002 ± 0.001

A. virdis

44 ± 12

8 ± 38

0.008 ± 0.002

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funding provided by    the Texas State Comptroller Office

butterflies