This website last updated April 9, 2013

Importance of Milkweed

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Importance of Milkweed


Milkweed is crucial to the life-cycle of the monarch butterfly. Female monarchs search for milkweed to lay their eggs. Monarch larvae (caterpillars) will only feed on milkweeds in the Asclepias family. There are 108 species of milkweed in North America. Monarchs are only known to use 30 of them, but they may use any or all of them. Below is a list of milkweeds that Monarchs favor in Arizona. They are labeled whether they are more likely to grow in the low or high desert areas of the state.

Most species of milkweed contain cardiac glycosides. When the caterpillars consume the leaves, they become toxic to many predators. This protection continues when they become butterflies. Predators learn to avoid monarch larvae and butterflies because they taste bad or make them vomit. There is a wide variation in toxin strength in different kinds of milkweed.

Table of contents


Arizona Milkweed (Asclepias angustifolia)
 Antelope Horn or Spider Milkweed (Asclepsias asperula)
 Tropical Milkweed Blood Flower (Asclepias curassavica)
 Engelmann’s Milkweed (Asclepias engelmanniana)
 Desert Milkweed (Asclepias erosa)
 Broadleaf or Popcorn Milkweed (Asclepsias latifolia)
 Pine-needle Milkweed (Asclepias linaria)
 Mojave Milkweed (Asclepias nyctaginifolia)
 Zizotes Milkweed (Asclepias oenotheroides)
 Showy Milkweed (Asclepsias speciosa)
 Rush or Desert Milkweed (Asclepsias subulata)
 Horsetail Milkweed (Asclepias subverticillata)
 Butterfly Weed (Asclepias tuberosa)

Tropical Milkweed
Blood Flower
(Asclepias curassavica)

Low Desert
(considered an annual in AZ)
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Butterfly Weed
(Asclepias tuberosa)

High Desert
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Pine-needle Milkweed
(Asclepias linaria)

Low Desert
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Desert Milkweed
(Asclepias erosa)

Low Desert
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Mojave Milkweed
(Asclepias nyctaginifolia)

High and Low Desert
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Horsetail Milkweed
(Asclepias subverticillata)

High and Low Desert
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Arizona Milkweed
(Asclepias angustifolia)

Low Desert
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Engelmann’s Milkweed
(Asclepias engelmanniana)

High Desert
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Zizotes Milkweed
(Asclepias oenotheroides)

High and Low Desert
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Rush or Desert Milkweed
(Asclepsias subulata)

Low Desert
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Antelope Horn or Spider Milkweed
(Asclepsias asperula)

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Broadleaf or Popcorn Milkweed
(Asclepsias latifolia)

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Showy Milkweed
(Asclepsias speciosa)

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