Ways You Can Help Monarch Butterflies and Other Pollinators

Many gardeners are concerned about helping to support insects that pollinate plants, especially the monarch butterfly (Danaus plexippus) due to its continuing decline.  In this article, we will cover the many ways that gardeners can help monarch butterflies.  The Xerces Society for Invertebrate Conservation reports that the western monarch population has collapsed. The Xerces Society’s winter 2025 count tallied only about 12,260 monarchs overwintering along the California coast, one of the lowest totals ever recorded, down from roughly 200,000 in 2018 and about 1.2 million in the late 1990s.

One major reason for the decline is the loss of milkweed (Asclepias species) in farm fields throughout the monarch butterfly’s range from Mexico to Canada. Once considered purely a nuisance weed in agriculture, milkweed has become scarce in farm fields due to the use of the herbicide glyphosate that kills weeds but not crops genetically modified to withstand the chemical.

Fortunately, there are many ways home gardeners can help monarch butterflies and other insects that make food and flowers possible by spreading pollen from one plant to another. These actions include planting plentiful milkweeds and nectar plants, becoming aware of predators, and using chemicals carefully in gardens.

Planting Monarch Habitat

Milkweeds produce nectar loved by many pollinators, including bees, beetles, butterflies, hoverflies (they look like tiny bees), and moths. Monarchs drink milkweed nectar. However, the plants are particularly important to them, because milkweeds are the only plants on which monarch butterflies lay eggs. In addition to food, all butterflies need host plants for their babies.

The U.S. Fish and Wildlife Service offers a wealth of information about how to help monarch butterflies including a seven-step plan for growing pollinator gardens containing milkweeds and “a diversity of plants that bloom throughout the seasons.”

Milkweeds

The U.S. Department of Agriculture Plants Database page for milkweeds (Asclepias L.) includes distribution maps of 76 kinds of milkweed either native or common (“introduced”) to parts of the U.S. To see the maps, click on the “subordinate taxa” tab.

Fifteen of the species are native to California and two are non-native species commonly grown throughout the state. An example of a popular native species in Southern California is Mexican whorled milkweed (Asclepias fascicularis), which has narrow leaves and creamy pink blossoms.

Milkweed flowers are shaped like stars. They’re tiny but make a big statement in gardens due to growing in clusters at the top of plant stems. While some types of Asclepias have pale flowers, others — such as the Southern California favorite non-native called tropical milkweed (A. curassavica) — bloom bright orange and gold.

Many sources note that tropical milkweed is long blooming and particularly alluring to monarchs, so it does a great job of feeding them. However, in warm-winter climates it acts like an evergreen that is leafy all year round. The problem with this lushness is that the plant may encourage monarch butterflies to linger up north instead of migrating to winter grounds in Mexico. Scientific research indicates that it is best to keep the plant trimmed to the ground during winter to avoid this situation. Otherwise, it becomes a vector for the spread of a parasite called Ophryocystis elektroscirrha or OE due to heavy traffic from a large population of overwintering monarchs.

Protective Toxins. Milkweeds contain chemicals called cardiac glycosides that are harmful to many animals. These substances don’t hurt the caterpillars of monarchs or their close relatives, the queen butterflies (Danaus gilippus) that also lay eggs on milkweed leaves. When the eggs hatch, the larvae eat the leaves and become toxic to many predators.

Fake Milkweed Danger. The conservation organization Monarch Joint Venture notes that a European relative of milkweeds — black swallow-wort (Cynanchum louisea) — is dangerous to monarch butterflies. It is a plant you won’t find in garden centers and an invasive species in several states, including California.

Butterflies identify plants by look, smell, and taste. Unfortunately, black swallow-wort — which has clusters of tiny, deep purple, star-shaped flowers — fools monarch mothers into thinking it is a milkweed. But their babies starve, because they can’t feed on its leaves.  So, weed these invaders no matter how pretty they are.

Native vs. Tropical Milkweed

Milkweed type	Examples	Winter behavior in SoCal	Risk to monarchs	Recommendation
Native milkweed	Narrowleaf (Asclepias fascicularis), showy (Asclepias speciosa)	Dies back in fall and winter	Low	Best choice, plant freely
Tropical milkweed	Asclepias curassavica	Stays evergreen in mild winters	Can spread the OE parasite and disrupt migration	Avoid, or cut back to a few inches in fall

Nectar Plants

Before further discussing foods that monarchs favor, it’s necessary to note that Green Thumb has a number of garden centers, and not all will have every plant we mention in an article on hand at the same time. Many flowering annuals, perennials, shrubs, and trees at our five Southern California garden centers are nectar sources for butterflies and moths. But sometimes the availability of plants we mention in our blog vary by center, or stock runs out. Please forgive us if this is ever the case. We’ll do our best to let you know if, when, and where the plants you want are available.

In addition to milkweeds, monarch butterflies love the nectar of flowers ranging from American natives, such as Agastache (commonly called hyssop), to nonnatives like Zinnia. In-between that A to Z range, you’ll find low-water California natives, including light purple-flowered favorites like Cleveland sage (Salvia clevelandii) and California lilac (one of 56 Ceanothus shrubs native to our state).

Butterfly favorites come in a broad range of colors, but yellows and golds make especially pretty companions with purple flowers. Two examples of California natives that monarchs favor are lanceleaf tickseed (Coreopsis) and goldenrod (Solidago).

Here are some helpful lists of top monarch choices from butterfly organizations:

• A mix of American native and nonnative species
• California coast natives and
• Inland California natives.

Becoming Aware of Predators, Parasitoids & Parasites

Although the sap of milkweeds makes monarchs unpalatable or even dangerous to many creatures, some attackers have adapted to the toxins. Becoming aware of these seemingly invincible enemies may help you to minimize their presence in the garden by (1) spreading out plantings of milkweed throughout your yard to minimize concentrations of attackers, (2) avoiding the purchase of biocontrol insects known to attack monarch butterflies, and, in some cases (3) removing the villains by hand (be sure to wear gloves) or with a butterfly net.

Monarch eggs, larvae, pupae (chrysalises), and adults are subject to dangers including:

• Predators, such as carnivorous beetles, birds, lacewing larvae, lizards, mantids (praying mantis is one), and spiders.
• Parasites, such as fungal and bacterial pathogens that infect hosts and can’t live away from them.
• Parasitoids, which are tiny creatures such as certain kinds of tachinid flies and wasps, that lay their eggs on or in other insects’ bodies.

Here is a helpful article from the University of Minnesota’s Monarch Lab describing the main natural enemies monarch butterflies face. Many are considered beneficial in gardens, because they minimize infestations of pests — such as spider mites and aphids — that kill flowering plants. Trying to eliminate beneficials from your garden could unbalance your backyard ecosystem.

Two beneficial insects that may spook human observers the most are tachinid flies and mantids, which are valued for biological control of insects that harm crops. But they become pests themselves when they kill monarch young.

Out of about 10,000 species, 12 types of tachinids attack monarch butterflies. Tachinids insert their eggs into caterpillars where they live and feed until ready to pupate. They exit their host’s dead body on thin threads and go on to become flies and repeat the cycle.

Unlike tachinids, a mantis immediately kills its prey by eating it and attacks a wide range of beneficial creatures as well as pests. Although they consume harmful insects, mantids eat too many beneficials — from hummingbirds to monarchs — for efficient, biocontrol targeting of pests.

It’s possible to handpick larval tachinids by removing leaves on which they are laid. However, due to its large size, a praying mantis may be easier to catch either as an egg sack on a branch or wall or as an adult hanging out in its favorite hunting grounds — pollinator gardens. Nevertheless, a praying mantis or another kind of adult mantid may be hard to see at first, because they look like leaves until they leap.

When you locate one, The Cornell Cooperative Extension of Oneida County suggests laying a butterfly net over or next to it and “gently” tapping it into the net.  What comes next? The Extension service doesn’t say. But try not to retaliate even if you saw it chomp off the head of a beautiful monarch. Maybe you could put it in a shoebox with holes in the lid, collect a few more of its buddies, and deliver them someplace where there are no milkweeds.

Avoid Using Chemicals in Wildlife Landscapes

Chemicals that harm bad guys in the garden also harm the good guys, including monarch butterflies and other pollinators.

One of the most important things you can do to protect monarch butterflies is to avoid applying pesticides and herbicides in your garden and landscape. If you absolutely must use some substance to get rid of an invasion, seek the gentlest agent possible, such as a soap spray. When visiting a Green Thumb Garden Center, ask questions about products and their application before purchase.  You can also contact us by phone or online. We’ll help you make informed decisions about pollinator plants and pest solutions.

Monarch Butterflies and Pollinators: FAQs

How can you help monarch butterflies?

Plant native milkweed and seasonal nectar flowers, and avoid pesticides. Milkweed (genus Asclepias) is the only plant monarch caterpillars can eat, so it is essential host habitat, while nectar flowers feed the adults. In Southern California, choose native milkweeds such as narrowleaf milkweed (Asclepias fascicularis) and plant a mix of flowers that bloom across the seasons.

Do monarchs only eat milkweed?

Monarch caterpillars eat only milkweed, but adult monarchs drink nectar from many different flowers. Because the larvae are milkweed specialists, a monarch garden needs milkweed as a host plant plus a range of nectar plants to support the adults through the season.

Is tropical milkweed bad for monarchs in California?

In Southern California’s mild winters, non-native tropical milkweed (Asclepias curassavica) can do more harm than good. It stays evergreen instead of dying back, which lets the OE parasite build up on its leaves and can encourage monarchs to breed over winter instead of migrating. The Xerces Society recommends planting native milkweed instead. If you already grow tropical milkweed, cut it back to a few inches in fall and keep it trimmed through winter.

What is a pollinator garden?

A pollinator garden is a space planted with a variety of flowers, ideally natives, that gives pollinators food, water, shelter, and host plants across the seasons. For monarchs that means pairing nectar flowers with milkweed, the host plant their caterpillars depend on.

What plants do monarch butterflies need in Southern California?

Monarchs need two things: native milkweed for their caterpillars and nectar flowers for the adults. Good SoCal choices include narrowleaf milkweed (Asclepias fascicularis) and showy milkweed (Asclepias speciosa) for host plants, plus low-water California natives like Cleveland sage, California lilac, and goldenrod for nectar.

How many monarch butterflies are left?

Western monarch numbers have fallen more than 95 percent since the 1980s. The Xerces Society’s winter 2025 count tallied only about 12,260 monarchs along the California coast, one of the lowest totals ever recorded, driven mainly by habitat and milkweed loss, pesticides, and climate change.

Sources:

• Xerces Society, Western Monarch Count
• Xerces Society, Tropical Milkweed
• Monarch Joint Venture, Milkweed FAQ
• U.S. Fish and Wildlife Service, Pollinator Gardens

Written by Alicia R.

 

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