Skip to Content
Frequently Asked Questions
Wendy caldwell ducks 6 30 077

Milkweed

Does milkweed need to be in bloom to attract monarchs?

No, milkweed does not need to be in bloom to attract monarchs for egg laying. In the spring, female monarchs often lay eggs on very young milkweed plants. Throughout the summer, monarchs will use milkweeds even if they do not flower or when they are finished flowering. Visit this Journey North article for more information on how monarchs find milkweed. Milkweed flowers do attract many pollinators when in bloom because they are a great nectar source. 

Is milkweed a weed? Are there limitations to where it can be planted and what types of milkweed are preferred by monarchs?

 Despite their name, milkweeds are wildflowers. There are over 73 species of milkweed native to the United States, and about 30 species are used regularly by monarchs. Most species grow in specific regions of the country. Those who are interested in growing milkweed should plant milkweed native to their region. Planting native, locally sourced, species helps ensure that the plants you purchase are best suited to your region. Visit www.plantmilkweed.org for more information on planting milkweed for monarchs. 

Are there other species aside from monarchs (insects or otherwise) that consume milkweed? If so, how do I prevent this from happening, or at the very least limit the amount of competition for milkweed in my yard?

There several species of mammals and insects eat milkweed (see additional post for more details). Milkweed is part of a complex ecosystem that supports many kinds of creatures! Planting large amounts of milkweed will help reduce the competition for milkweed between monarchs and other species as well as any competition for milkweed between monarch larvae. You can also try planting several patches of milkweed in different areas to help distribute the consumption between areas. 

Can I transplant milkweed?

It is possible, but not always easy or successful. It is best to transplant milkweed when plant shoots are very small. Milkweed has a deep tap root and if you cut off too much the transplant is less likely to succeed. If you find small plants that are likely growing from seeds dispersed the year before, these will be much easier to transplant! If you do try to transplant milkweed, make sure that you get as much of the taproot as possible, and do not take all of the plants from the site you are transplanting from. If you are interesting in transplanting a plant from the wild or somewhere not on your property, seek permission before doing so.

Are all milkweed species toxic?

Yes, all milkweed species contain cardenolides, or cardiac glycosides, making them toxic. Species do, however, differ in level of toxicity. For example, common milkweed, Asclepias syriaca,  has a much lower cardenolide concentration than tropical milkweed, Asclepias curassavica.

What are some symptoms of diseased milkweed plants, and how do I treat plant disease?

We certainly aren't plant experts, but diseased plants is something that does come up on occasion. Some symptoms of diseased or unhealthy milkweed plants could include unusual spots on the leaves, misshapen or asymmetrical leaves or pods, or sometimes plants can appear wilted or weakened. These things can be caused by a number of different fungi or bacteria, but it is usually a good first step to look for tiny insects on the undersides of the leaves that may be eating the plant (not aphids). If these tiny thrips or mites are present on the undersides of the leaves, you can try to spray the undersides of the leaves with a strong dose of water. If you suspect a fungus or bacteria in your plants, you can try cutting back anything that looks diseased. If this doesn't work, consult with a local garden club or native plant nursery to see what they recommend. 

How can I encourage the sale of pesticide-free milkweed?

Insecticides are known to reduce monarch caterpillar growth and survival and affect butterfly flight and navigation. It is critical to avoid using pesticides, especially systemic insecticides, on milkweed and nectar plants and to use an integrated pest management approach. Systemic insecticides, such as neonicotinoids, are generally harmful to monarchs and other beneficial insects, and have persistent effects that last long after the plants are purchased. Read more about concerns with monarchs and pesticides here.

Well-educated consumers can really make a difference in driving demand for pesticide-free plant materials. In order for companies that grow and sell plants to justify an investment in different species or techniques, they go through an intensive process trying to evaluate the short- and long-term market to determine how profitable (or not) that investment will be.

Raising your voice is an important way that you can show demand for pesticide-free milkweed. Use the resources below as tools to reach out to your nursery and express your desire to purchase pesticide-free milkweed. You can do this by asking to speak to the store manager, submitting an inquiry on the store website, posting a review on the internet, or any other venues available to contact the store management.

If you believe you have purchased treated plants, contact the store you purchased the plants from to find out, and if so, express your desire for pesticide-free plants. This will help them know that their consumers do not want to purchase treated plants. You can also find more pointers for what else you can do here.

How can I identify milkweed plants?

Milkweed plants belong to the family Asclepiadaceae. Monarchs feed almost exclusively on milkweed in the genus Asclepias, of which there are approximately 110 species in North America. Milkweed is perhaps most well-known for its milky sap or for the latex contained within its leaves. You can break a leaf to see if a plant you suspect to be milkweed has milky sap. Be careful not to ingest or get milkweed sap in your eyes. Several other characteristics can help you identify milkweed. The unique and intricate structures of milkweed flowers are also very useful for identifying milkweed species. Milkweeds have floral whorls of sepals and petals, with a unique third whorl of 5 hoods. Each hood encloses a horn, which is the modified filaments of a flower’s anthers. For pollination, milkweeds rely on butterflies, moths, bees, ants, and wasps. Milkweed produces seed pods, or follicles, as its fruit. These pods split at one suture to release up to hundreds of seeds. The exact properties of milkweeds’ flowers, stems, and leaves varies with each species. For photos and information about the specific milkweed species native to your area, check out the Monarch Watch’s milkweed profiles page, and Monarch Joint Venture’s Plant Milkweed for Monarchs pdf. We also have a whole suite of milkweed resources on our Downloads and Links page.

Where can I find milkweed?

Milkweed plants are perennials, which means that an individual plant lives for more than one year and will sprout in the spring from both rootstock and seeds. Because of this milkweed will grow in the same general area year to year, although its exact location can shift. Look for milkweed in regularly disturbed areas, and areas of native landscaping. For example, check local parks, nature reserves, along alleys and sidewalk boulevards, rain gardens, prairie, and (safely) roadsides. In the Midwest, milkweed used to grow abundantly in prairies, and later within and beside agricultural fields. However, due to habitat loss from changing land use practices, their numbers have decreased. To learn more about the milkweed species native to your area and where to find them, visit the Biota of North America Program’s distribution maps, the Monarch Watch’s milkweed profiles page, and Monarch Joint Venture’s Plant Milkweed for Monarchs pdf. Perhaps the easiest way to find milkweed though is to plant some in your own garden! It is especially important to plant more milkweed now, to help bring back milkweed for monarchs. We recommend planting milkweed species native to your area whenever possible, as it is most suited to your climate and requires the least maintenance. Use The Xerces Society’s Milkweed Seed Finder to help you find seeds in your state. For a brief how-to flyer on planting milkweed in your garden, download MJV's Gardening for Monarchs pdf. For a detailed guide to planting milkweed, see the Monarch Watch’s Growing Milkweeds page.

How much has milkweed growth diminished?

Milkweed growth has decreased substantially in the Midwest over the past 10-20 years, especially in agricultural areas treated with herbicides. Some studies estimate the decline in milkweeds to be over 58% since 1999 (Pleasants and Oberhauser, 2013). As of 2014, only 1.34 billion milkweed stems remained from the estimated 2.2 billion milkweeds present in 1999 (Pleasants, 2016). 

Are milkweed bugs harmful to monarchs?

If you've ever looked closely at your garden, you've most likely noticed a wide variety of insects. Large and small milkweed bugs are very common in milkweed patches and can sometimes be found on monarch larvae and pupae. Large milkweed bugs are herbivorous - they feed on the leaves, stems, and seeds of milkweed using their long proboscis. Because large milkweed bugs only eat milkweed, they should not be a problem for monarchs. Small (common) milkweed bugs are mostly herbivorous, but can occasionally be scavengers. These insects have been reported feeding on a wide variety of other insects, such as honey bees, monarch caterpillars and pupae, and dogbane beetles. While it may be disappointing to see monarch eggs, larvae or pupae preyed upon, this is all part of a vibrant milkweed ecosystem. Try not to kill the small milkweed bugs you find in your garden, their presence in the ecosystem is important!

Does milkweed yellows phytoplasma harm caterpillars?

Phytoplasmas are bacteria and are species specific. This means that they would not be able to live inside the caterpillars. These phytoplasmic organisms on milkweed are not known to harm caterpillars. They cause disease in plants and are spread by insects that feed on the phloem of plants, like leafhoppers. For more information on milkweed yellows phytoplasma, visit the Monarch Lab webpage: (https://monarchlab.org/?/resources-links/blog/milkweed-yellows-phytoplasma)

Is milkweed an invasive weed?

There are many species of milkweed native to North America and while “weed” is part of their name, these milkweeds are native, beneficial wildflowers. In the U.S., neither the federal government nor any states list milkweeds as noxious weeds. In fact at least five species are listed as state or federal endangered species (Borders, LeeMäder 2014). According to the North American Invasive Species Network, an invasive species is “a non-native species...whose introduction causes or is likely to cause  economic harm, environmental harm, or harm to human health.” The invasiveness of any plant depends on the characteristics of the species and where it is planted. Some species of milkweed, like common milkweed (Asclepias syriaca), have a tendency to be more aggressive in garden settings or disturbed areas, and thus have a reputation of being “weedy”. If you are concerned about milkweed spreading too much, choose species that are native to your area, and avoid  species that are particularly good at vegetative, clonal reproduction or are prolific seed producers. Local garden centers, Master Gardeners or Master Naturalists, and other conservation authorities can help you choose the most appropriate native milkweed species to plant in your setting.

Is milkweed only good for monarchs?

Despite their natural toxicity, milkweeds are utilized by a variety of insect species. Butterflies, moths, bees, and wasps and more visit milkweeds for pollen and/or nectar. Regional studies examining milkweed pollination found over two dozen insect species using milkweeds; and results indicate that honey bees, bumble bees, other large bees, large wasps, and larger butterflies were the most important milkweed pollinators (Borders, Shepherd 2011). Likewise, there are species that consume milkweed leaves or seeds, like milkweed beetles (Tetraopes tetrophthalmus), large milkweed bugs (Oncopeltus fasciatus), and tussock moths (family Lymantriidae). Predators, such as crab spiders (family Thomisidae) and mantises (order Mantodea), prey on the many insect species that frequent and depend upon milkweed. These multi-species relationships are all part of the milkweed ecosystem. The Milkweed, Monarchs and More field guide by Rea, Oberhauser and Quinn has more information on inhabitants of the milkweed patch. For these reasons, milkweeds are an important component in any pollinator mix for restoration projects. This answer, and answers to other milkweed questions, can be found on the Monarch and Milkweed Misconceptions handout.

Why isn't the milkweed growing in my habitat flowering?

Different species of milkweed have different growth strategies, so it depends on what species you have. In general, milkweed may not flower in the first year of growth, because it is investing its resources in growing a strong root system. Also, if there is excess nitrogen in the soil the plant may not flower, so do not fertilize milkweed. Finally, milkweed may not bloom if the plant is stressed, such as by drought or excessive heat. Luckily, monarchs will lay their eggs on milkweed even if it is not flowering! The caterpillars eat the leaves of the plant, so your milkweed can still be a host plant without flowers. Milkweed may also spread through its root system (depending on the species), so the plant may spread that way despite not flowering or going to seed.

What should I do if I haven't seen any monarchs in my milkweed patch?

Because monarchs are distributed across a very wide range, and there are so many fewer monarchs than there were previously, it can take a long time for monarchs to find a patch of milkweed. However, if you live in the monarch's breeding range, your milkweed is important! It is vital to get as much milkweed as possible out on the landscape, so that they monarchs that are out there are the most likely to find viable habitat in which to breed.

There are a few things you can do to make your habitat more enticing to monarchs, which may help them find your habitat.

  1. Plant a variety of species of milkweed. This allows females various types of milkweed to choose from as a host for their eggs. Find species of milkweed native to your region here, and sources of milkweed plants can be found at www.plantmilkweed.org.
  2. Plant a variety of flowers that bloom throughout the season. Adult monarchs need to eat the nectar from flowers. For regional recommendations of monarch-preferred nectar flowers, see the Xerces Society Monarch Nectar Guides.
  3. Provide shelter from the wind, and sunny places for monarchs to bask. This handout provides other general recommendations on gardening for monarchs to consider.
How can I collect, save, and share my milkweed seeds with friends and family?

If you want to harvest your milkweed seeds to share or donate, here are a few things to keep in mind:

  • Remember to only collect local, native milkweed seeds!
  • Always identify the species prior to harvesting and clearly mark the container you keep them in (Suggested label: Your name, date, species common and/or scientific name, location of collection)
  • It’s best to only collect a portion of the seeds in the area you find milkweed so that the milkweed can continue to propagate your area! (Recommendation: collect 1/3 of the seeds and leave 2/3)
  • Know when to collect! This is important because the seeds need to be ripe in order to germinate. If the seeds are white or pale, they are not ready yet. Keep an eye out for browning on the pod. When ready, the seed pods will easily split open.
  • After collecting the seed pods, leave them out to dry in an open, dry area. Once the pods are dry, open them to collect the seeds. There will be a silk-material that needs to be removed before storing. You can remove this by hand or by placing the seeds and silk material in a paper bag. Shake vigorously to separate the seeds. Cut a small hole in the bottom corner to shake out seeds. To see how to remove the silk by hand, watch this video.
  • Once the seeds are stripped of the silk material, store them in a cool, dry place away from mice and insects! (Plastic baggies or glass or plastic jars work well.)

You can also check out this article from the Native Plant Society of Texas for more information on how to harvest milkweed seeds. 

How can I tell if a plant is milkweed or dogbane?

Another plant, dogbane (Apocynum cannabinum), looks strikingly similar to common milkweed (Asclepias syriaca). This look-alike can leave people disappointed if they're expecting monarchs on their milkweed, but it turns out not to be the right plant! Here's a few ways they're similar, and how to tell them apart.

Similarities: Both plants have milky sap if you break off a leaf, and their growth pattern is very similar. Both have opposite and oval shaped leaves.

Differences: Common milkweed has a hairy stem, unlike dogbane. When mature, the dogbane stem branches in the upper portion of the plant. The flowers also look quite different. Common milkweed flowers are pinkish, large and ball shaped, whereas dogbane flowers are whitish green and in small clusters.

What's eating my milkweed?

Despite milkweed's toxicity, there are many creatures other than monarchs that eat the leaves of this amazing plant. Deer and rabbits have been reported to eat milkweed leaves, and there are many other insects that feed on milkweed such as milkweed bugs, tussock moths, queen butterfly larvae, and more. Nectar and pollen from milkweeds are important food sources for many pollinators, in addition to monarch butterflies. In addition to attracting pollinators, milkweeds support a wide variety of insects that attack crop and garden pests (Milkweed: A Conservation Practitioners Guide). For more information on the milkweed ecosystem, visit http://monarchjointventure.org/resources/downloads-and-links/ and click on Milkweed Resources. A great field guide to what's in the milkweed patch is Milkweed, Monarchs and More (Ba Rea, Karen Oberhauser, and Michael Quinn).

How can I grow milkweed from seed?

Milkweed seed can be planted directly in soil, or started indoors. You can sow milkweed seeds by scattering them on the soil surface 1/4-1/2 inch apart, and then cover them with about 1/4 inch of additional soil. Water the area frequently after planting until plants become established. Many species need to be vernalized (cold treated) before planting. Vernalized seeds can be planted in the spring after the danger of frost has passed. Non-vernalized seeds can be planted in the fall, and nature will provide the cold treatment. See Monarch Watch's milkweed propagation guide for further recommendations, information on vernalization and instructions for starting milkweed seeds indoors.  Also watch our Monarch Conservation Webinar: Growing Milkweed for Monarch Conservation (scroll down to May 2016) to hear from Chip Taylor of Monarch Watch on milkweed growing techniques and best practices. For further details on milkweed growing and conservation use, visit the Xerces Society's Milkweed Practicitoner Guide, which is a complete guide to milkweeds, including biology/ecology, propagation, benefits to wildlife, and use in restoration projects.

Is milkweed harmful to grazing livestock?

Milkweed does contain toxic cardiac glycosides, but rarely pose a significant threat to people or animals. A small taste of milkweed is typically not fatal to animals, but can be dangerous if large quantities are consumed. If sufficient forage is available in grazing lands, milkweeds are generally not sought after. According to the USDA, poisoning typically occurs in areas of poor forage where milkweed is abundant. Prepared feeds and hay should not contain high concentrations of milkweed. For more information, please refer to our MJV handout: Monarch and Milkweed Misconceptions.

Why are caterpillars disappearing from my milkweed patch?

There are a number of potential reasons for this. If disappearing caterpillars are 5th instar caterpillars, odds are they moved away from your milkweeds to find a safe place to form their chrysalis (they typically do not pupate on milkweed plants). If earlier instars or eggs are disappearing, a more likely culprit is a monarch predator. You can read more about natural enemies on our website. Researchers agree that less than 10% (with some studies as low as 2%) of monarch eggs reach adulthood. 

Where can I find free or low cost milkweeds and nectar plants?

Here is more information on finding funding for your monarch project. There is also information about finding milkweeds native to your area on our website, www.plantmilkweed.org. You may also apply for Free Milkweeds for Restoration Projects through Monarch Watch's Milkweed Market. 

Don't forget to check with friends, neighbors, or your local garden club to see if anyone has seeds from native milkweeds or other wildflowers that they have collected and would be willing to share. Some forbs (flowering plants) may also be easy to split or transplant if someone you know is looking to get rid of them.

My monarchs are eating dill or parsley! What's going on?

What you are looking at is not a monarch, since monarchs only eat milkweed (genus Asclepias). We get this observation and question quite often, because the caterpillars of the black swallowtail butterfly resemble a monarch caterpillar. Black swallowtail larvae feed on a variety of different host plants, but cultivated garden plants like dill, parsley, celery, and fennel are a few on the list. If you come across a caterpillar that you don't know, try identifying the host plant that it is on. This may help you in determining what Lepidoptera (butterfly or moth) species you are dealing with!

What should I do if I can't find an appropriate source of local native milkweeds or nectar resources that are recommended for monarchs?

This reason for this problem comes back to the principles of supply and demand. The commercial availability of native milkweeds and nectar sources is driven by the demand for those resources and a response in the supply chain will not always be immediate. Producing native plant materials is a long-term process and can sometimes be a risky investment for plant producers if they aren't sure about the long-term demand for those plants/seeds. It is important that we continue to drive increasing demand for these native, locally sourced plant materials to increase their availability over time and hopefully to drive down the cost as well. Since supply is often limited for native milkweeds and nectar sources, get your orders/requests in early. If vendors sell out during the spring, they may begin taking pre-orders for the following fall or spring.

If you haven't already done so, make sure that your site is ready for planting. There are different methods for site preparation, such as solarization, you can use to ensure the area is as weed free as possible to increase the success of the native plants you are trying to establish. Even if native milkweeds are not available when you are ready to plant, establish a high-diversity mix with other native forbs and grasses. These habitats will still be beneficial to monarchs and other pollinators, and you can plan ahead to augment the habitat in years following with milkweed plants/plugs. Another option would be to use annuals or some sort of cover crop on the habitat area during that season. This could prevent weedy species or invasives from taking over a site that you have prepared for planting and will allow time for you to find an appropriate source of seeds or plants for the habitat. Depending on what is planted, it may also provide some floral resources for pollinators.

Where can I get milkweed seeds or plants that are most appropriate for my area?

Our web page, www.plantmilkweed.org, has many great resources and tips for locating native milkweed seeds and plugs across the U.S. The Xerces Society's Milkweed Seed Finder and Monarch Watch Milkweed Market provide a directory of vendors that distribute native milkweed seeds and/or plugs. In addition, the Milkweed Market offers trays of native milkweed plugs for purchase for different regions of the country (regional availability varies). We recommend using native milkweeds in all gardening or restoration projects. The commercial availability of native milkweed seeds or plants can be limited (varies by region), so to help build this market (increasing availability and driving down cost) we strongly encourage your support of the commercial market through purchasing native plant materials from a local native plant or seed producer.

How do I choose which species to plant for monarchs and where can I find local sources?

Native milkweeds and nectar plants are essential for monarchs. Monarchs need milkweed for egg laying and larval development and need nectar resources to support adult butterflies during breeding and migration. Both should be included in any monarch habitat. We recommend planting native, locally sourced species that are well-adapted for your region and more likely to thrive in your area's conditions. You can find information about how to choose which milkweed and nectar resources are right for you from our www.plantmilkweed.org website. This website also provides guidance on locating appropriate seed and plant materials near you, and considerations for different types of restoration or enhancement projects, like gardens or larger natural areas.

What should I do with my milkweed seeds?

If you have extra native milkweed seeds that you would like to share, here are some considerations: 

  1. Native milkweeds need to undergo cold/moist stratification or vernalization before they are able to germinate, so if you are sharing your seeds with others, make sure that you let them know the status of this so they know how to prepare or store the seeds prior to planting.
  2. This MJV FAQ and this article from the Native Plant Society of Texas discuss how to harvest milkweed seeds. 
  3. To build habitat connectivity for monarchs and other pollinators, offer your local, native milkweed or nectar plant seeds to friends and neighbors and encourage them to plant pollinator habitat. 
  4. To help strengthen commercial milkweed availability, connect with local native plant or seed vendors who may be interested in your seeds. 
  5. Connect with various community groups or chapters who own or have access to land where seeds may be put to good use. These include but are not limited to Pheasants Forever, Wild Ones, Master Gardeners/Naturalists, Extension programs, golf courses, archery or gun clubs, parks, schools, natural resources groups (soil and water conservation districts, etc.),  
  6. The Milkweed Market can use your native seeds. This program collects donated milkweed seeds and grows regionally appropriate milkweed plugs, which they distribute back to the region the seeds originated.
  7. Contribute to the national seed bank by participating in the Bureau of Land Management's Seeds of Success program. For more information about the national seed strategy, you can view the 2015 document here.     

Remember, the best thing you can do with your seeds is to plant them locally!

Why does my milkweed look diseased or yellow?

Disease isn't always the culprit when milkweed doesn't appear healthy. If there is a possibility that herbicide was applied in the general vicinity, this could potentially be a cause for unusual or sick-looking milkweed. If spray drift is unlikely the cause, there are many different diseases that affect milkweed, including everything from fungi to viruses. One common bacterial disease is called milkweed yellows phytoplasma. 

It can be difficult to identify what is affecting your specific plants, as there is no comprehensive diagnostic manual for milkweed diseases. The Xerces Society Milkweed FAQ provides some general advice about dealing with diseased milkweeds:

"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."

Specifically in regard to a common milkweed disease called "milkweed yellows phytoplasma":

Phytoplasmas are bacteria; they do not have a cell wall and are enclosed by a single membrane. They cause diseases in plants and are spread by insect vectors (primarily leafhoppers). Leafhoppers aren't the only insect that can spread phytoplasma, but most of the known vectors are in the insect order Hemiptera. Their piercing/sucking mouthparts allow them to feed on the phloem of plants, where phytoplasmas live. These phloem-feeding insect vectors can transfer diseases such as milkweed yellows phytoplasma by feeding on an infected plant, allowing an incubation period during which the phytoplasma cells replicate and eventually reach the insect’s salivary glands, and then moving to a healthy plant and injecting phytoplasma cells into it during feeding. How do you know if your milkweed has a phytoplasma disease? There are a few symptoms to look for, according the Phytoplasma Resource Center found on the USDA Agricultural Research Service website:

  •  Phyllody—development of leaf-like growths in place of normal flower parts
  •  Virescence—development of green color in place of normal flower color
  •  Witches Broom—abnormal, excessive proliferation of axillary shoots resulting in a broom-like growth
  •  Yellowing—leaves lose normal green color, becoming yellow
  •  Little leaf—development of abnormally small leaves
  •  Proliferation—abnormal growth of numerous stems
  •  Necrosis—death of cells and/or tissues
  •  Dieback—death of branches
  •  Stunting—overall reduction of plant height
  •  Bunch top—shortening of internodes at and near the tip of a branch, resulting in bunched growth at the end of the branch

What should you do if you suspect phytoplasma in your milkweed patch? Since the disease is spread by insect vectors, one way to get phytoplasma under control is to quickly and effectively eliminate any milkweeds suspected of phytoplasma, at the first sign of disease. By digging out an infected plant, you reduce the chances of other insects feeding on that plant and becoming vectors of the disease.

Do you have tips for growing milkweed? What do you recommend for me to be successful?

The Xerces Society provides an entire FAQ all about milkweeds! Read this for more valuable information on growing and establishing milkweeds. Xerces Milkweed FAQ 

Is foraging habitat for the adults more important than milkweed during the fall migration?

Milkweed is important throughout the growing season, since monarch larvae continue to develop on the host plants as the migration begins. However, nectar sources, or foraging habitat for adults during the fall (southbound) migration are extremely important. Adult monarchs that eclose starting around mid-August are in a state of delayed maturation called reproductive diapause. They focus on nectaring to fuel their migration rather than breeding and laying eggs on milkweed. For this reason, nectar sources are more important for adult monarchs during the fall migration. All monarch habitats should include a mix of local, native milkweed and nectar plants appropriate to your region. A variety of nectar plants should be planted so that your garden is blooming all season long. For information on creating habitat for monarchs visit www.plantmilkweed.org.

What is the best time to plant milkweed seeds?

Pollinator Plants of the Central US provides an overview of milkweed establishment practices for the lower Midwest and central United States. According to the document, milkweed seed should ideally be planted in the fall. While some seed predation will occur, exposure to cold temperatures and moist conditions during winter will stimulate germination. Spring planting is also possible but artificial stratification of the seed is recommended to enhance germination.

How do I get rid of pests, like aphids, from my garden or habitat? Are they hurting my monarchs?

Many people are concerned about infestations of insects in their garden or habitat; we get the most questions about aphids. There are a few key points to remember when thinking about pest control. First, with good quality habitat comes a higher diversity of insects using the site. This diversity is providing resources for a wide variety of wildlife using the habitat and overall contributes to the health of the ecosystem. Some of these insects may compete with monarchs for milkweed, or even kill monarchs, but we can trust that in a healthy and diverse ecosystem/habitat, some monarchs will evade predators and contribute to the population. Second, remember that almost all insecticides will kill more than just the target species. If you spray an area with insecticide to kill aphids, other insects (including monarchs) that are in the area will be affected. For this reason, we don't recommend using insecticides in your monarch or pollinator habitat.

If you have a severe issue with aphids on your milkweeds, the safest way to remove them is manually. While a high concentration of aphids on your milkweed may look "bad", these insects are not necessarily causing harm to monarchs; unless they are in extremely high density, there are usually not enough aphids to kill the plant. You can squish the aphids and then rinse the plants with water to dislodge them from the plant. Make sure to check for monarch eggs and caterpillars first! A mild solution of dish soap and water can also be used to kill aphids on milkweed plants (again, after monarchs have been removed). Spraying this solution directly onto the aphids effectively kills the insects. Rinse the plants about a day after they've been treated with this insecticidal soap to remove any residue or dead aphids. This method is only effective when the solution directly hits the target insects; it acts by blocking the spiracles, so the residue will not kill insects. You can find a variety of recipes for home made insecticidal soap online, using simple ingredients typically found in your home.

What are the potential problems associated with planting tropical milkweeds?

Research by Satterfield et al., 2015, shows very clearly that monarchs breeding on tropical milkweed throughout the winter have higher levels of protozoan infection (caused by Ophryocystis elektroscirrha, OE) compared to monarchs in the migratory cycle. Please see the Monarch Joint Venture Fact Sheet and our Q&A with monarch and tropical milkweed experts for more information about the potential risks of growing exotic milkweed for monarchs.

Do some areas already have ‘enough’ milkweed habitat?

Healthy and abundant habitat is essential for monarch and pollinator conservation. For monarchs, this habitat should contain milkweed because it is an essential host plant for their larvae to eat. While habitat without milkweed can also provide floral/nectar resources for monarchs (which are also very important), that habitat would not be able to support immature monarchs during their reproductive season. Thus, a habitat with a balance of both native milkweeds and other nectar plants will benefit monarchs and a variety of other pollinators and wildlife. Since one main goal of habitat restoration is to create an ecosystem that is able to sustain long-term and continue providing benefits to the organisms using the site, it is important that these habitats are diverse. Milkweeds are a part of this ecosystem and provide benefits to more than monarchs, so should be included in all habitat restoration projects, as should other wildflowers. Another consideration is habitat fragmentation, and what this means for monarchs in search of suitable breeding areas. Including and increasing habitat that includes milkweed across the landscape, regardless of area, will help to ensure that those monarchs in search of breeding habitat will find it more easily. Recovering from the recent record low population size may not happen in just a few years, so the more habitat available for reproduction, the better likelihood monarchs have of a population rebound.

Do monarchs utilize different types of milkweed? Which are preferred?

Monarchs utilize various milkweed species for oviposition and larval development, although certain species may offer more favorable conditions than others (Pegram & Melkonoff 2019). Research indicates that monarchs can thrive on different types of milkweed, with some preferences observed depending on factors such as cardenolide content, trichome density, and latex production. However, it's essential to note that while milkweed selection may vary, there can be fitness consequences associated with the chosen species. For instance, some milkweed species may support higher larval survival rates and faster development, but those are not always preferentially selected by ovipositing monarchs (Greenstein et al. 2022). Milkweed selection preference may also vary within the season (Damiano 2024).

The preference-performance hypothesis suggests an adaptive correlation between oviposition preference and larval performance, indicating that monarchs may choose certain milkweed species that optimize offspring success. However, environmental conditions (e.g., plant height, presence of other monarch eggs) and individual's past experiences with a milkweed species can influence female oviposition decisions, leading to preferences that may contradict the preference-performance hypothesis (Pocius et al. 2018, Jones & Agrawal 2019).

Native milkweed cultivars can also be effective in attracting and supporting monarchs and native bees, particularly in urban gardens. However, cultivars should not be planted in natural areas (Baker et al. 2020). 

Overall, for optimal support of pollinators like monarchs, a diversity of native milkweed species suitable for the growing conditions should be planted alongside other nectar- and pollen-producing plants. This approach can enhance biodiversity while contributing to monarch and native bee conservation efforts. 

The Monarch Joint Venture provides an overview of the priority species that we recommend for each region.