Mowing & Habitat Management

Is there any value to planting a garden of solely milkweed or do I have to mix in other flowering species to make a beneficial habitat?

 Having a garden full of milkweed is beneficial for monarchs. The best habitat for monarchs, however, contains a variety of native milkweed as well as nectar plants. While milkweeds are the only plants that monarch larvae can eat, the adult monarchs themselves do not eat only milkweed. Instead, they rely on the nectar from flowers. Having a combination of milkweed and other flowering plants helps ensure that adult monarchs will have a food source even when the milkweed plants are not in bloom. To find out what nectar and milkweed plants to buy visit Xerces Society’s Nectar Guides and our Plant Milkweed for Monarchs handout.

I live near the California overwintering grounds. Should I be planting milkweed in my yard?

It is not recommended to plant milkweed within 10 miles of the coast in central and northern California where milkweed did not occur historically. Instead, plant a variety of flowers native to your region that provide nectar from early spring through fall to support monarchs and other pollinators. See the Xerces Society for Invertebrate Conservation's Priority Action Zones in California for Recovering Western Monarchs to learn which monarch conservation actions are recommended in your region. 

Why is planting milkweed in coastal areas discouraged?

While monarchs require milkweed for egg laying and larval development during the late-spring and summer breeding season, during the overwintering period (approx. October-March), the butterflies are usually in reproductive diapause, which means they stop mating and laying eggs. During the winter, monarchs don't need milkweed, but they do need plants that provide nectar for energy and water to keep hydrated. 

Historic records suggest that milkweed was largely absent from most coastal areas of California. Because of the mild winter temperatures, milkweed planted close to the coast can often escape hard frosts and persist through the winter instead of dying back. Persistent winter milkweed encourages monarchs to continue mating and laying eggs, which disrupts their natural annual life cycle (halts winter diapause) and comes with numerous negative consequences. This phenomenon is well documented in Florida, the Gulf Coast, and Southern California, where non-native, tropical milkweed (A. curassavica) stays evergreen and is associated with winter breeding. In coastal California, even native species may act like tropical milkweed--staying green late into the fall-- and cause similar issues as tropical milkweed.

Negative consequences of winter breeding in monarchs include the following:

• OE levels in winter-breeding monarchs have been documented up to 9 times higher than OE levels in non-breeding, overwintering monarchs (Satterfield et. al., 2016). This has two primary potential outcomes to consider: Monarchs that become heavily infected with OE may die outright; and individuals that don’t die immediately have been shown to have reduced fitness but can live long enough just to further spread OE within the population – thus reducing the fitness of even more individuals.
• When monarchs are congregated at an overwintering site and milkweed is present (so breeding is possible), the large number of adults can overwhelm the comparably small amount of milkweed with eggs, resulting in all or most of the larvae starving to death. In this way, milkweed near overwintering congregations can serve as a population sink (lost reproductive potential). 
• Another potential outcome is if milkweed near overwintering groves persists into the fall and early winter, just long enough to encourage breeding and egg-laying, and then dies off or goes dormant later in the winter, all or most larvae on that milkweed would starve.

The goal of monarch conservation is to increase the stable population size, and it is important to do so in a manner that supports a sustainable population as well as the natural life cycles of the monarch (including summer migration and winter breeding diapause). In wild populations, there are numerous natural factors at play, which tend to favor the strongest and most fit individuals – which, in turn, is important for the health of the entire population. Artificial or temporary boosts to population numbers resulting from human interventions that "save" individual butterflies that would have otherwise died can negatively affect the genetic health of the entire population.

If you'd like to learn more about monarch overwintering sites, please read our overwintering page. Explore our About Monarchs section for monarch life cycle and ecology information.

Check out Xerces Monarch Nectar Guide for coastal California for ideas of what to plant, and the State of Overwintering Sites Report for additional information.

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.

I don't see many chrysalises, but I do see some caterpillars. Why is this?

You're not alone if you haven't seen many monarch chrysalises in the wild. Monarch caterpillars usually move away from the milkweed plant they were eating when they are ready to pupate, or form their chrysalis. Chrysalises are found on a variety of different plants and structures within the habitat, like benches, windowsills, and other nearby plants or bushes. If you had been seeing large instars and expect they should have transitioned into the chrysalis stage but haven't seen any, don't fret. It is rare to find monarch chyrsalises in the wild, so just because you didn't see them doesn't mean they weren't successful. Keep records about what you are observing through programs like the Monarch Larva Monitoring Project, www.mlmp.org. If you find monarchs one week and the late instars are gone by the next week and you aren't successful in finding their chrysalis, use your knowledge about monarch biology to watch for freshly eclosed (emerged) adult butterflies about 10 days later.

What can I do to support monarchs and pollinators with a few acres of land?

Create habitat with a mix of native wildflowers (including milkweeds) and grasses. You can plant native plants in a more typical garden setting or plant a prairie garden or natural area. Think about areas on your yard that could be maintained with native prairie plants - they don't always have to be gardens! Native prairie plants, once established, require much less maintenance than a typical mowed lawn, and provide tremendous benefits to local pollinators. Find locally sourced native plant materials, and collaborate with groups like Pheasants Forever, Wild ones, or Master Naturalists/Master Gardeners to help plant and maintain the habitat! For more resources visit our downloads and links page.

What is the most appropriate time to cut tropical milkweed back?

It is recommended to prune the milkweed stalks to about 6 inches in height during the fall and winter months to discourage monarchs from establishing winter-breeding colonies. Cutting back the milkweed will also help to eliminate OE spores that may be present on the plant. Re-cut the milkweed every few weeks as leaves re-sprout. Tropical milkweed might pose fewer problems in the northern monarch breeding range because it dies back naturally when it freezes.

These recommendations are not applicable in south Florida (south of Orlando), where a distinctive, non-migratory population of monarchs has long been established. However, native milkweed planting is still encouraged in this area.

For more information on tropical milkweed, read the our handout on the topic.

My milkweed habitat should be mowed to cut back the woody vegetation that is encroaching. Is there a safe time to do this that will be less harmful to monarchs?

Yes! The MJV has a handout called Mowing: Best Practices for Monarchs. We used community science data and ground-tested it with researchers and volunteers across the country to come up with recommendations for times when management activities may be safer for monarchs. It is important to note that this handout looks strictly at monarchs, so if you have prioritized additional plant or animal species to protect at your site, make sure to consider timing that works best for all! Because monarch timing can vary slightly from one year to the next, it is also important to keep an eye on the status of the migration through Journey North to see how this year's timing might be different from other years. Most importantly, avoid mowing or disturbing the entire habitat at once so that you leave untouched areas for wildlife using the habitat to recolonize.

I thought monarchs were migratory, so why am I seeing monarch caterpillars during the winter?

There is a small non-migratory population of monarchs in southern Florida, but the vast majority of eastern and western monarch populations do undergo a long-distance migration to their overwintering grounds. Overwintering monarchs are typically in a state of reproductive diapause (delayed reproductive maturity) and become reproductive in early spring as they prepare for the return journey to their breeding grounds.

However, some monarchs skip the traditional long-distance migration. In parts of the southern U.S. and California, the year-round persistence of milkweed in good condition, typically the non-native tropical milkweed (Asclepias curassavica), allows monarchs to breed throughout the winter, as indicated by community science observations of eggs and larvae during winter months. Scientists don't know exactly what causes monarchs to be reproductive and to forego their long-distance migration. It could be exposure to the tropical milkweed, or some other factor, perhaps warmer conditions or even poor physiological condition in the monarchs themselves.

While we don't know why they stay, we do know that year-round tropical milkweed patches, and the year-round breeding that they allow, foster greater transmission of the protozoan Ophryocystis elektroscirrha (OE). Therefore, we recommend that tropical milkweed should be cut back in the winter and fall months in the southern U.S. and California, and should be gradually replaced with native milkweeds as they become available.

Researchers at the University of Georgia, through Project Monarch Health, have been working with community science volunteers to document OE trends in monarch populations, with a focus on how winter breeding behavior impacts disease prevalence. For more information on the parasite and how to participate in this research, visit the project website (www.monarchparasites.org). Learn more about the potential risks of growing exotic milkweeds for monarchs on this MJV handout or Expert Q&A. 

Should I use solarization to prepare my site for planting monarch habitat?

Solarization is one method of preparing a site for planting. This guide by the Xerces Society outlines restoring habitats from seed, and includes the solarization process. One of the webinars in the MJV Monarch Conservation Webinar Series also addresses this topic. 

Why are monarchs in southern Florida non-migratory?

A warmer climate and the continuous availability of milkweed (for larvae/breeding) and nectar (for adults) allow monarchs to persist and breed year-round in southern Florida. The extent to which there is interchange between the south Florida population and the eastern population during migration seasons is unknown.