Milkweed FAQ

Do you have a question about milkweed? Hopefully one of the questions below will help you out.

  1. Should I plant milkweed? View answer
  2. Which milkweed species is best for planting in my area? View answer
  3. How and when should I plant milkweed, for best success? View answer
  4. How should I clean and/or collect milkweed seed? View answer
  5. Is tropical milkweed (Asclepias curassavica) bad for monarchs? What is the Xerces Society’s position on this milkweed species? View answer
  6. There are orange aphids on my milkweed plants. What are they and should anything be done to control them? View answer
  7. Do milkweeds have pest problems? View answer
  8. Why do my milkweed plants look sick? View answer
  9. There is a large patch of milkweed on my property (or on nearby property owned or managed by the city, county, etc.). What could I (or the landowner or land manager) do to best manage the plants for the benefit of monarchs? View answer
  10. I’ve heard that milkweeds and other pollinator plants available from nurseries are sometimes treated with pesticides that may poison or kill insects that feed on the plants. How do I know whether milkweed plants that I might purchase have been treated? View answer
  11. I think I have milkweed growing on my property but I’m not sure. How can I positively identify the plants? View answer
  12. Are milkweeds toxic to animals? Which animals are most likely to eat the plants? View answer
  13. Are milkweeds weedy? If I plant them on my property, will they spread outside of their planted area and cause a problem for me or my neighbors? View answer
  14. How many milkweed plants do I need to have to attract and support monarchs? View answer
  15. Does the Xerces Society have milkweed seed or plants to sell or give away? View answer
  16. Can the Xerces Society provide funding or recommend a source of funding to cover the cost of 1) planting milkweed, 2) becoming involved with growing and distributing milkweeds, or 3) launching an educational and outreach campaign around monarchs and milkweeds? View answer
  17. Can I hire the Xerces Society to help me establish habitat for monarchs and/or pollinators? View answer
  18. Does the Xerces Society want information on the locations of milkweed populations or of monarch sightings? View answer

  1. Should I plant milkweed?
  2. Milkweeds are the required host plants for monarch butterfly caterpillars (female monarchs lay their eggs on milkweeds) and their flowers provide nectar for bees, butterflies, and other beneficial insects. By planting milkweed, you can provide habitat for monarchs and also attract and support pollinators. Within the United States, the Xerces Society recommends planting milkweed species that are locally native and for which regionally-sourced seeds and plants are available. Several milkweed species occur across nearly all regions of the continental United States, except western Washington, northwestern Oregon, Alaska and Hawaii (although monarchs have become naturalized in parts of Hawaii, where they breed on introduced Asclepias species and two close relatives of milkweeds, Calotropis gigantea and C. procera). Beyond U.S. borders, milkweeds are native to southern Canada and to Mexico, but we do not have detailed information about the plants’ distribution in these countries.

    Monarch butterflies are more common in some parts of the United States than others and milkweed seed supplies are variable across regions. Information on monarch population dynamics and milkweed seed availability by region can be found in Appendix IV of the Xerces Society document Milkweeds: A Conservation Practitioner’s Guide. Our Milkweed Seed Finder allows you to search for seed sources by state and by species.

  3. Which milkweed species is best for planting in my area?
  4. The Xerces Society recommends planting milkweed species that are locally native and for which regionally-sourced seeds and plants are available. Milkweeds are not native to Alaska and Hawaii, but are native to most of the continental U.S. with the exception of western Washington and northwestern Oregon. It is important to learn which milkweeds are native to your region: please consult these milkweed range maps from the Biota of North America Program’s (BONAP) North American Plant Atlas. On these maps, dark green indicates that a species is present within the state and bright green shows that a species is documented to occur in that specific county. Please refer to BONAP’s map color key to learn the meaning of additional colors displayed.

    Once you know which species are native to your area, you can use our Milkweed Seed Finder to search for seed sources. However, seed supplies are limited in some regions. Of the more than 70 milkweed species that are native to the U.S., fewer than 20 are typically available from commercial sources. In the Southeast, the Northern and Southern Plains, the Intermountain West, the Southwest, and the Pacific Northwest regions, sources of milkweed seeds and plants are currently scarce.

    If you cannot find milkweed plant materials that originate from your region, we recommend instead planting native wildflowers that will provide a source of nectar for adult monarch butterflies. Monarchs require flower nectar to fuel their flight, mating, and egg-laying. For plant recommendations, please visit our Pollinator Conservation Resource Center, select your region, and then click to expand on the ‘Recommended Pollinator Plants’ tab.

    Additional Resources

    This fact sheet by the Monarch Joint Venture highlights species to plant on a broad, regional basis. However, please note that a few of the featured species are not reliably available for purchase as either seed or live plants.

    For region-by-region recommendations of priority milkweed species for monarch habitat restoration efforts and descriptions of seed availability, please see Appendix IV of the Xerces Society document Milkweeds: A Conservation Practitioner’s Guide.

  5. How and when should I plant milkweed, for best success?
  6. Milkweed seed can be sown directly in the ground or used to start seedlings in pots or flats. Here, we describe both methods, tailored for small-scale plantings such as home or school gardens. For planting methods relevant to implementing large-scale restoration projects or establishing seed production fields, please refer to the Xerces Society document Milkweeds: A Conservation Practitioner’s Guide. Whether you will be hand-sowing seed or transplanting seedlings, removing weeds from the planting area is essential to ensure successful milkweed establishment. For guidance on planting site preparation, please refer to the Xerces Society document Establishing Pollinator Meadows from Seed or our series of Pollinator Habitat Installation Guides.

    Overview of milkweed life cycle

    Milkweeds native to the U.S. are perennial and with few exceptions, they are deciduous. The plants typically flower between late spring and the end of summer. Following seed dispersal, their aboveground growth dies back to the ground. They then remain dormant through the winter, and re-emerge in the spring from established root systems.

    Please note that newly established plants may not flower and produce seed in their first year. If female monarchs pass through your area, they will still be able to find the plants (to lay eggs on them) even if they do not have flowers.

    Direct sowing

    Following site preparation to remove weeds, seeds can simply be scattered onto the soil surface by hand. To achieve seed to soil contact, you can then press the seeds into the soil surface with a garden trowel or the soles of your shoes. In most regions, fall planting is a good approach because the seeds’ exposure to cold, moist conditions during winter and spring will help stimulate germination. Seeds can also be direct-sown in early spring if temperatures are still low and the soil is still moist. In comparison, direct-sowing seed during the late spring or summer will be less effective and is not recommended. In regions where precipitation is irregular (e.g. southwestern U.S.), planting should precede anticipated rainfall.

    If you have missed the fall or early spring planting window but do not want to wait several months to plant, you can artificially “stratify” the seeds by storing them under moist conditions in a refrigerator because doing this simulates wintry soil conditions. Instructions on how to stratify seed are available from various gardening webpages and are featured on pages 28 – 29 of the Xerces Society document Milkweeds: A Conservation Practitioner’s Guide. It is important to note that once stratified seed has been planted, the soil in the planted area must be kept moist for the duration of the germination period. Milkweed seedlings will need supplemental water during their first year, particularly during the summer months, but mature, established plants typically will not require watering.

    Seedling propagation

    Growing your own seedlings is far more labor intensive than direct-sowing seed, but the process can be fun and rewarding and compared to plants established from seed, transplants are typically more competitive against weeds and are likely to flower sooner.

    In their early growth phase, milkweeds devote a significant amount of energy to root development. Using the deepest containers or plug trays available will help accommodate their root growth and may increase transplant survival.

    Before sowing milkweed seeds in pots or trays, it can be helpful to first “stratify” the seed for a few to several weeks. Stratification is an easy-to-perform treatment in which seed is stored under moist conditions in a refrigerator. This simulates wintry soil conditions and often results in more rapid, even seed germination. Instructions on how to stratify seed are available from various gardening webpages and are featured on pages 28 – 29 of the Xerces Society document Milkweeds: A Conservation Practitioner’s Guide. It is important to note that once stratified seed has been planted, the soil in the planted area must be kept moist for the duration of the germination period.

    It’s difficult to predict how long it will take to grow seedlings that are robust enough for transplanting. The propagation timeline will vary across species and also depends on ambient temperature and the size and type of containers used. Seedlings may be ready to transplant within as little as eight weeks but some species may require several months. There are no hard and fast rules around this, but it is best to transplant seedlings that have several “true leaves”, and larger seedlings will likely have higher survival rates. If you have a target transplanting date in mind, you can estimate the propagation timeline and work backward. For example, if seed is stratified for four weeks and seedlings are then grown for eight weeks, the stratification process should be started approximately three months prior to the target transplanting date. Please note that this is a conservative timeline, since seedling propagation may take longer than eight weeks.

    Transplanting should occur after the threat of frost has passed and should also be timed to avoid periods of hot, dry, or windy weather. Seedlings should be watered immediately after transplanting and are likely to need watering throughout their first year, particularly during the summer, to aid establishment. If seedlings are grown indoors, moving them to a shadehouse or other protected outdoor location for a few days prior to transplanting will help acclimate them to outdoor conditions and reduce transplant shock. This process is known as “hardening off” and various gardening websites provide more detailed instructions.

  7. How should I collect and/or clean milkweed seeds?
  8. Please refer to the Xerces Society document Milkweeds: A Conservation Practitioner’s Guide for instructions on collecting and cleaning milkweed seed. We recommend separating the seeds from the attached floss fibers before planting or storing milkweed seed. Storing seed pods fully intact for more than a few days is not recommended as this may foster mold growth, particularly if the floss and pod shells contain moisture and if humidity is high.

  9. Is tropical milkweed (Asclepias curassavica) bad for monarchs? What is the Xerces Society’s position on this milkweed species?
  10. Tropical milkweed is not native to the U.S. but is sold by many plant nurseries and is frequently planted in gardens. It is used as a host plant by monarchs (and other milkweed-associated butterflies) both where it has been introduced in the States and where it naturally occurs beyond U.S. borders. Yet, preliminary research suggests that tropical milkweed’s presence in the U.S., particularly at southern latitudes, may encourage monarchs to lay eggs outside of their regular breeding season, thus disrupting their migratory cycle (Batalden & Oberhauser 2015), and increase the prevalence of monarch infection by the protozoan parasite Ophryocystis elektroscirrha, commonly referred to as “OE” (Satterfield et al. 2015). These potential negative impacts on monarchs stem from the fact that tropical milkweed may have foliage year-round when it grows where winters are mild and adequate moisture is available (such as in the Gulf States and parts of California). In contrast, the majority of native U.S. milkweeds are summer or fall-deciduous and do not have foliage during late fall and winter. Though tropical milkweed potentially remains evergreen when growing in the southern U.S., in regions where winter temperatures frequently fall below freezing, such as in the northeastern U.S., tropical milkweed behaves as an annual species and is typically frost-killed. When this occurs, tropical milkweed does not have foliage during the winter and there is no potential for parasite spores to build up on the plants. To mimic this effect and prevent harm to monarch health, people who live in the southern U.S. and who already have tropical milkweed in their gardens are advised to cut the plants back to the ground during early fall.

    For additional information, please refer to this fact sheet and Q&A article by the Monarch Joint Venture.

    The Xerces Society recommends only planting locally native milkweed species, and thus we do not recommend planting tropical milkweed, even when sources of native milkweed plants and seeds are scarce. Beyond concerns about tropical milkweed’s potential negative impacts on monarch health, there is potential for the species to escape from cultivation, where growing conditions are favorable, and pose a threat to native plant communities.

    References

    Batalden, R. V., and K. S. Oberhauser. 2015. Potential changes in eastern North American monarch migration in response to an introduced milkweed, Asclepias curassavica. In Monarchs in a Changing World: Biology and Conservation of an Iconic Butterfly, edited by K. S. Oberhauser, K. R. Nail, and S. Altizer, 215–224. New York: Cornell University Press.

    Satterfield, D. A., J. C. Maerz, and S. Altizer. 2015. Loss of migratory behaviour increases infection risk for a butterfly host. Proceedings of the Royal Society B: Biological Sciences 282 (1801), 20141734.

  11. There are orange aphids on my milkweed plants. What are they and should anything be done to control them?
  12. The oleander aphid (Aphis nerii) is unfortunately a common pest of milkweeds in many parts of the United States. The species is believed to be native to the Mediterranean region but is now considered to be invasive in several warm temperate and tropical regions of the world (Harrison & Mondor 2011). With their piercing-sucking mouthparts, the aphids feed on sugary liquids within the plants’ tissues. Their feeding activity will not always kill the plants but it does potentially weaken them and can impact the plants’ ability to flower and produce seed.

    Aphids reproduce at an extremely rapid rate and their numbers can potentially reach several hundred per plant stem. Early detection and control can help prevent a major outbreak. Yet, it can be tough to decide whether and how to control oleander aphids to protect plant health. When aphid numbers are few, they can potentially just be removed by hand. Some people have reported success with blasting aphids off of plants with a strong stream of water from a garden hose. Yet, when monarch butterfly eggs and/or caterpillars are present on aphid-infested plants, there unfortunately is no aphid control strategy that will not also potentially impact monarchs. Applying insecticidal products (of any kind) will harm monarch eggs and caterpillars and if the plants are flowering at the time of application, pollinators that visit milkweed flowers may also be harmed. Moreover, it can be difficult to effectively control aphids with insecticide because they often feed on the undersides of leaves and in small crevices between plant parts, which are difficult areas to reach when spraying insecticide. Any aphids that are left alive following insecticide application will rapidly reproduce and their numbers will rebound fairly quickly. In particular, we recommend against using insecticides that have “systemic” action to control oleander aphids. These products (with active ingredients such as imidacloprid, dinotefuran, clothianidin, and thiamethoxam) are designed to be long-lasting and their persistence in plant tissues can poison or kill insects, such as monarch caterpillars, that feed on the plants.

    Natural Pest Control

    Insects including lady beetles (both larval and adult stages), hoverfly larvae, and lacewing larvae are predators of oleander aphids. Also, at least two species of braconid wasps parasitize and kill oleander aphids. These natural enemies of aphids may occur in your area and in some cases, may help keep the aphids in check so that you will not need to control aphid outbreaks. Please keep in mind that applying insecticide to milkweed plants will harm these beneficial insects that play a role in aphid control. Note that the Xerces Society does not recommend purchasing lady beetles and releasing them for the purpose of controlling oleander aphids; there is little evidence that this is effective and there can be unintended ecological consequences to releasing insects.

    To read a more detailed profile of the oleander aphid, please refer to the Xerces Society document Milkweeds: A Conservation Practitioner’s Guide.

    Reference

    Harrison, J. S. and E. B. Mondor. 2011. Evidence for an invasive aphid “superclone”: extremely low genetic diversity in oleander aphid (Aphis nerii) populations in the southern United States. PLoS ONE 6(3): e17524. doi:10.1371/journal.pone.0017524

  13. Do milkweeds have pest problems?
  14. Yes, although milkweeds contain toxic chemicals that help protect them from herbivory, several insects (in addition to monarch butterfly caterpillars) are specially adapted to feed on milkweeds. As described above, the introduced oleander aphid (Aphis nerii) can be a significant pest of milkweeds. Native insects that feed on milkweeds and that can sometimes reach densities high enough to be regarded as “pests” include leaf-feeding beetles (Chrysochus cobaltinus, Labidomera clivicollis, Tetraopes spp.), seed-feeding bugs (Lygaeus kalmii and Oncopeltus fasciatus), and a stem weevil (Rhyssomatus lineaticollis). Please refer to the Xerces Society document Milkweeds: A Conservation Practitioner’s Guide for detailed profiles of these milkweed herbivores.

  15. Why do my milkweed plants look sick?
  16. Like all organisms, milkweeds are susceptible to disease but information on how to diagnose and treat the diseases of most wild native plants is limited. The diverse pathogens that attack milkweeds are broadly representative of those that attack all plants, consisting of bacteria, fungi, viruses, and other microscopic organisms such as protozoa. Please see Appendix II of The Xerces Society document Milkweeds: A Conservation Practitioner’s Guide for a list of over 40 documented milkweed pathogens. However, there are potentially many more as-yet-unrecognized milkweed diseases.

    It will likely be difficult to positively identify the disease afflicting your milkweed plants. A diagnostic manual for milkweed diseases is unavailable as are treatment recommendations for specific diseases. While some plant pathologists such as with University Extension programs may have familiarity with milkweed diseases, most are likely to have expertise that focuses on the diseases of economically important plants such as major food crops.

    When milkweeds in home gardens or landscape features display symptoms of infection, removing and disposing of the diseased tissue will help prevent the infection from spreading to healthy plants.

  17. There is a large patch of milkweed on my property (or on nearby property owned or managed by the city, county, etc.). What could I (or the landowner or land manager) do to best manage the plants for the benefit of monarchs?
  18. Best management practices for maintaining the health and habitat value of milkweed stands include protecting them from: herbicide application, insecticide application and drift, and frequent mowing and/or burning. Herbicides will damage or kill the plants and insecticides can harm or kill the flower visitors that pollinate milkweeds and the monarch caterpillars that feed on milkweed foliage. While infrequent and strategically-timed disturbance can potentially benefit milkweeds and monarchs, repeated disturbance (such as frequent mowing) will deplete the plants’ energy stores, may kill monarch caterpillars that are feeding on the plants, and could remove the plants from the landscape at a time of year when monarchs need them for egg-laying sites and as a source of flower nectar.

    While there is not currently any comprehensive guidance available on the optimal timing of milkweed disturbance to enhance monarch habitat, a couple of studies have provided important insights. In the southern Great Plains, research showed that prescribed burning conducted in July can stimulate milkweed growth in time to support monarchs in late summer (Baum & Sharber 2012). In the absence of burning, the milkweeds would have typically senesced during August and would not have been available to monarchs in late summer. Similarly, in upstate New York, mowing during July stimulated milkweed regrowth and monarchs laid proportionally more eggs on the fresh growth than on older, unmown plants (Fischer et al. 2015). More research of this nature is needed to gather information on the optimal timing of vegetation management for monarchs in additional regions.

    If maintenance activities such as mowing, spraying, or burning must be conducted where milkweed grows, the landowner or land manager could consider adjusting the timing of those activities to minimize disturbance during the time when monarchs are most active in the region. However, this idealized timing may not be possible to achieve in regions such as California where monarch caterpillars are potentially present on milkweeds from spring through fall. In all regions, mowing in the late fall, after migrating monarchs have left, is a sound approach to preventing harm to monarchs. If it is not possible to adjust the timing of vegetation management, for example due to a need to meet safety or contract requirements, it is ideal to disturb only a subset of the total area occupied by milkweed. This will leave some milkweed habitat intact for monarchs and the other pollinators that rely on the plants. A final consideration is that mowing milkweeds when they are in flower or have immature seed pods will be particularly detrimental to the plants because they are expending significant energy toward reproduction at that time and may have more difficulty recovering from the disturbance. For an overview of monarch population dynamics in various regions of the country, please see Appendix IV of the Xerces Society document Milkweeds: A Conservation Practitioner’s Guide.

    References

    Baum, K. A. and W. V. Sharber. 2012. Fire creates host plant patches for monarch butterflies. Biology Letters 8:968–971.

    Fischer, S. J., E. H. Williams, L. P. Brower, and P. A. Palmiotto. 2015. Enhancing monarch butterfly reproduction by mowing fields of common milkweed. American Midland Naturalist 173:229–240.

  19. I’ve heard that milkweeds and other pollinator plants available from nurseries are sometimes treated with pesticides that may poison or kill insects that feed on the plants. How do I know whether milkweed plants that I might purchase have been treated?
  20. In recent years there has been a large-scale adoption of new “systemic” insecticides by the horticultural industry, often driven by demand for plants free of insect damage. Unlike older classes of insecticides that were typically sprayed onto plants to kill pests on contact, systemic insecticides are absorbed into and translocated throughout the plants. This mode of action provides long-lasting protection against pests such as aphids, but also makes treated plants toxic to invertebrates that feed on pollen, nectar, leaves, and other plant tissues. In the specific case of milkweeds, these chemicals can harm or kill the flower visitors that are needed for pollination and seed set and the butterfly caterpillars that feed on milkweed foliage.

    The most widely used class of systemic insecticides is the neonicotinoids, which are synthetic chemicals that are similar in structure and action to nicotine. They work by blocking nerve impulses in insects and other invertebrates. Imidacloprid, dinotefuran, clothianidin, and thiamethoxam are examples of neonicotinoids that are sold for use on farms and in gardens.

    Although there is no focused effort to track neonicotinoid use on milkweeds within the nursery industry, there have been anecdotal reports of monarch caterpillars being sickened or killed by feeding on nursery-purchased milkweeds. It is unfortunately not possible to tell from visual inspection whether a plant contains systemic insecticides. Before buying milkweeds or other pollinator-attractive plants, we strongly recommend asking nursery or garden center staff whether the plants have been treated. If they are unable to provide an answer, you may want to exercise caution in making a purchase. Retail outlets that are not directly involved with plant propagation may not have information about insecticide use readily available; nurseries that grow their own stock, especially smaller local native plant nurseries, will be in a better position to provide such details.

    To protect the health of monarchs and other pollinators, it is also important to avoid using over-the-counter systemic insecticides on your property! Read more about that here.

  21. I think I have milkweed growing on my property but I’m not sure. How can I positively identify the plants?
  22. Milkweeds’ flowers and seed pods are very distinctive and thus it is easiest to positively identify the plants when they are either flowering or bearing pods. Photos of milkweeds are featured in the Xerces Society’s various milkweed publications (please visit www.xerces.org/milkweed) and on numerous websites.

    Milkweed flower color is variable across species and can be white, yellow, green, purple, pink, orange, or red. However, the structure of milkweed flowers is consistent, with each flower consisting of two main parts. The showy, upper part—where nectar is stored—is called the corona and always has five structures called “hoods” (hood shape varies across species). Five petals, together called a corolla, form the lower part of the flower and are reflexed backward in most species.

    Milkweed species vary widely in leaf shape, size, and arrangement. Some species’ leaves and stems are covered in soft hairs while others are hairless. Across species, milkweeds are variable in stature, with some plants being tall and stout while others are low-growing and sprawling. Some species are colony-forming and grow in dense stands while others grow in multi-stemmed clumps or as scattered individuals.

    With the exception of butterfly milkweed (Asclepias tuberosa), milkweeds ooze white sap when their tissues are damaged. You can check for the presence of sap by tearing off a small piece of leaf and observing whether sap oozes from the torn area. It is important to avoid any contact of the sap with your skin, eyes, or mouth. However, note that milkweeds are not the only plants with milky sap. For example, common dandelion, milk thistle, sow thistles, leafy spurge, and wild lettuce, all of which are widespread, weedy species, also have milky sap.

  23. Are milkweeds toxic to animals? Which animals are most likely to eat the plants?
  24. Milkweeds contain complex chemicals called cardenolides which help defend the plants from herbivores, parasites, and pathogens. Monarch caterpillars and other milkweed specialist herbivores have physiological adaptations that allow them to sequester cardenolides and use them in their own defense against predators. However, cardenolides can be toxic or lethal when ingested by animals (including humans) that cannot metabolize or sequester them.

    Milkweeds are potentially toxic to livestock such as sheep, cattle, horses, and goats (Panter et al. 2011). Of these animals, sheep and goats are the most likely to be poisoned because they are browsers and often prefer to feed on weeds over other forages (Dwyer 1978, Kingsbury 1964). For some milkweed species, consumption of less than 1% of an animal’s body weight in fresh material can be a lethal dose (Kingsbury 1964). Milkweed poisoning has also been documented in chickens and turkeys, but avian species are less likely to eat milkweeds than grazing mammals (Panter et al. 2011).

    There are a few reports of black-tailed jackrabbits, pocket gophers, and deer occasionally browsing milkweed. Yet, the potential for backyard wildlife to be poisoned by eating milkweeds is largely unknown. The risk of milkweed poisoning to dogs and small children is undocumented but likely low since the plants are bitter-tasting.

    Beyond consumption of milkweed, the plants’ milky sap is a skin and eye irritant. It is important to avoid any contact of the sap with the skin, eyes, and mouth.

    For more information, please refer to the Xerces Society document Milkweeds: A Conservation Practitioner’s Guide.

    References

    Dwyer, D. D. 1978. Impact of poisonous plants on western U.S. grazing systems and livestock operations. In Effects of Poisonous Plants on Livestock, edited by R. F. Keeler, K. R. Van Kampen, and L. F. James, 13–21. New York: Academic Press.

    Kingsbury, J. M. 1964. Poisonous Plants of the United States and Canada. 626 pp. Englewood Cliffs, NJ: Prentice Hall.

    Panter, K. E., M. H. Ralphs, J. A. Pfister, D. R. Gardner, B. L. Stegelmeier, S. T. Lee, K. D. Welch, B. T. Green, T. Z. Davis, and D. Cook. 2011. Plants Poisonous to Livestock in the Western United States. (Agriculture Information Bulletin No. 415.) 107 pp. Logan, UT: U.S. Department of Agriculture, Agricultural Research Service, Poisonous Plant Research Laboratory.

  25. Are milkweeds weedy? If I plant them on my property, will they spread outside of their planted area and cause a problem for me or my neighbors?
  26. Though the plants’ common name implies that they are weeds, milkweeds are a diverse group of native wildflowers. A few milkweed species colonize disturbed areas and are considered weeds by some authorities (e.g., Southern Weed Science Society, Western Society of Weed Science, and Nebraska Department of Agriculture), but Asclepias species are not listed as noxious weeds at either the state or federal level in the U.S.

    In addition to reproducing by seed, some milkweed species reproduce vegetatively by sending up new shoots from roots that have spread a few to several feet outward from the parent plants. The species that exhibit this clonal reproduction are most likely to be occasionally perceived as weeds because their populations can expand over time. Of all the species, common milkweed (Asclepias syriaca) exhibits the highest degree of clonal reproduction. Other species known to reproduce vegetatively, but typically to a lesser degree than common milkweed, are horsetail milkweed (A. subverticillata), narrowleaf milkweed (A. fascicularis), plains milkweed (A. pumila), prairie milkweed (A. sullivantii), showy milkweed (A. speciosa), and whorled milkweed (A. verticillata).

    While it is possible that some milkweed species will spread outside of their planted area, any unwanted plants can simply be removed by hand-pulling (however, please take care to avoid any contact of the plants’ milky sap with the skin, eyes, or mouth). When it comes to home gardens and landscaping, milkweeds are unlikely to present an ongoing, unmanageable weed problem.

  27. How many milkweed plants do I need to have to attract and support monarchs?
  28. There is unfortunately no exact answer to this question! It’s unknown how many plants are ideally needed to make it easy for monarchs to find milkweed patches as they move through the landscape. The University of Minnesota Monarch Lab estimates that it takes about one mature milkweed plant to feed one monarch caterpillar. Yet, milkweed species are variable in leaf shape and size and they produce new growth at different rates, following herbivory. Also, monarchs sometimes lay multiple eggs on a single plant. More information is needed on this subject!

  29. Does the Xerces Society have milkweed seed or plants to sell or give away?
  30. No, the Xerces Society doesn’t sell milkweed and we are not able to provide free milkweed plant materials. To find sources of milkweed seed, please use our Milkweed Seed Finder directory. For regional lists of native plant nurseries that may carry milkweed, please visit our Pollinator Conservation Resource Center.

  31. Can the Xerces Society provide funding or recommend a source of funding to cover the cost of 1) planting milkweed, 2) becoming involved with growing and distributing milkweeds, or 3) launching an educational and outreach campaign around monarchs and milkweeds?
  32. The Xerces Society does not have any funding to allocate toward milkweed planting and propagation efforts or monarch conservation campaigns. Sources of funding for these types of projects are typically limited. We can point you in a few potential directions but since new funding sources may emerge, we also encourage you to do regular web searches for grant opportunities.

    Habitat grants may sometimes be available from your local Conservation District. Native Plant Societies occasionally provide small grants to establish monarch habitat in home gardens. Agricultural producers who meet certain criteria may be eligible for enrollment in conservation programs through the Natural Resources Conservation Service that provide cost-share assistance to enhance wildlife habitat. To inquire about eligibility, please contact your local USDA Service Center.

  33. Can I hire the Xerces Society to help me establish habitat for monarchs and/or pollinators?
  34. Yes! If you are an agricultural producer, you can hire Xerces to develop a custom Pollinator and Beneficial Insect Conservation Plan for your farm. Some farms may be eligible to receive this service at reduced or no cost when contacting us through the USDA Natural Resources Conservation Service. To determine your eligibility for a “Conservation Activity Plan” through the Environmental Quality Incentives Program (EQIP), please visit the NRCS website. If you are not an agricultural producer, please contact Eric Lee-Mäder, Pollinator Program Co-Director, to explore options for habitat restoration services.

  35. Does the Xerces Society want information on the locations of milkweed populations or of monarch sightings?
  36. Yes, if you live in Arizona, California, Idaho, Nevada, Oregon, Utah, or Washington, we would be grateful if you would report milkweed locations and/or your observations of breeding or migrating monarchs using this brief web survey. Compared to the eastern U.S., little is known about where and when monarchs breed in the western states. The data we are collecting through this survey is being used to help the many agencies and organizations engaged in monarch conservation to best target habitat enhancement and restoration projects in the western U.S. The Xerces Society has recently partnered with the four western regions of the U.S. Fish & Wildlife Service (USFWS) to model habitat suitability for the western monarch population, using the milkweed occurrence data that we have collected through our web survey. If you regularly conduct monarch and/or milkweed surveys and have more detailed information to share with the USFWS, please consider using this Excel spreadsheet to enter your data.

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In Your Pollinator Garden


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Plant Milkweed Seed!


Milkweeds support monarch butterflies, native bees, honey bees, and other beneficial insects. Search for sources of milkweed seed now!

Pollinator Conservation Resource Center


The Resource Center is where you can find regional information about plant lists, habitat conservation guides, and more. Learn more.