Milkweed: Essential for pollinators and wildlife

Perennials are essential to grow due to many reasons such as sustainability, cost-effectiveness, and environmental benefits. Milkweed (Asclepias spp.) is key to assisting pollinators. It offers food and shelter for many insects, the most famous of which is the monarch butterfly. With its colorful flowers and milky sap, milkweed is a lovely garden addition and an important symbolic plant for the environment. 

Pollinator populations, including monarch butterflies, are plummeting. That decrease is tied to habitat loss, pesticide use, and climate change. The Xerces Society for Invertebrate Conservation estimates that the eastern monarch population has decreased by more than 80% over the past 20 years, while the western population has fallen by 99%.

The caterpillar of the monarch butterfly feeds exclusively on milkweed, as it can't live without. Without milkweed, there is great concern for the future of these butterflies. Growcycle provides supplies and gardening products, such as milkweed, that may help gardeners grow perennials.

Botanical Profile

Milkweed (Asclepias spp.) is a group of diverse perennial plants that are critical for supporting pollinators. These plants differ in size, flower color, and habitat preferences, but they possess certain structural similarities, such as their familiar leaves, unique flowers, and milky sap.

1. Growth Habit and Structure

Milkweed plants tend to be tall and skinny, with upright or spreading growth habits, which vary by species. They can grow between one and six feet tall and have thick, slightly hairy stems that offer structural support.

2. Leaves and Foliage

Most milkweed species have opposite or whorled leaves found in pairs along the stem or  circular arrangements. The plant leaves are usually long, lanceolate, or oval and have smooth or slightly wavy edges. That is the main food of the monarch caterpillar, which consumes them in the larval stage.

3. Flowers and Pollination

Milkweed is renowned for clusters of tiny star-shaped flowers. These flower colors vary depending on the species and can be pink, purple, white, orange, or yellow. The flowers grow in closed umbrella-shaped heads and produce adequate nectar, attracting bees, butterflies, and other pollinators.

4. Toxic Sap and Defense Mechanism

When the stems or leaves of milkweed are ruptured, they excrete a thick, white, latex-like sap. This sap contains toxic substances known as cardiac glycosides, harmful to people and animals if ingested. Still, these toxins are a natural defense mechanism for monarch caterpillars, rendering them unappetizing to most predators.

5. Seed Pods and Propagation

After blooming, milkweed plants grow elongated seed pods. When mature, these pods burst open to release large amounts of seeds covered in silky white fibers (floss). The seeds' lightweight fibers enable them to be blown away by the wind, allowing them to cover more area and ensuring the plant propagates naturally.

Popular Milkweed Species

North America is home to over 100 types of milkweed with different characteristics and growing needs. Some of the more popular and widely planted varieties include:

Ecological Importance of Milkweed

Milkweed is essential in ecosystems, especially as a food and habitat for diverse pollinators and wildlife. It is a native perennial plant that provides food for these insects, helping to diversify and stabilize local food webs.

1. Support for Pollinators

Milkweed is the only host plant for monarch butterfly eggs and larvae and thus is an irreplaceable part of their life cycle. Female monarchs punctuate where the caterpillars will find milkweed, and thus their only food source. Without a supply of milkweed, monarch caterpillars wouldn’t survive, causing another decline in monarch populations.

It also produces nectar-rich flowers that attract a range of pollinators, from bees and butterflies to hummingbirds and beetles. Pollinators help to perform this so that it achieves successful reproduction. The flowers of milkweeds have a very specialized structure that includes sacs of pollen (called pollinia) and complicated appendages that make pollination highly efficient for the plant and its visitors.

2. Wildlife Benefits

Milkweed is an essential plant for several advantageous insects, namely:

• Bees and butterflies that rely on its nectar for food
• Predatory insects, including ladybugs and lacewings, feed on aphids and other pests.
• Insects, including beetles and ants, support the aeration of soil and the decomposition of plants.

Milkweed is poisonous to much of the animal kingdom, but some organisms, including certain beetles and tussock moths, have evolved to cope with it. These insects provide food for local birds and predators, helping manage local food chains.

3. Role in Ecosystems

Milkweed is one of the primary food sources for primary consumers (monarch caterpillars, beetles, and other herbivorous insects). It has a vital role in supporting local food webs in natural landscapes. These insects allow secondary consumers, including birds, amphibians, and small mammals, to maintain a balanced system.

It helps give us soil health by:

• Reducing erosion with its deep root system, which helps stabilize the soil.
• Replenish soil nutrients as milkweed leaves decompose.

Growing Milkweed: Best Practices for Gardeners

Milkweed is an easy-to-grow, hardy perennial that will grow well under a variety of conditions. Understanding the best practices for planting, propagation, and maintenance can help to develop healthy plants that benefit both pollinators and wildlife.

Ideal Growing Conditions

Milkweed is adaptable to multiple environments, but proper growing conditions will support healthy plants, provide long-lasting blooms, and provide food for pollinators for the rest of the growing season.

• Soil Requirements: Milkweed likes medium to dry, well-drained soil. It is pH tolerant (4.8–7.2) and thus can grow in some areas. This limits the possibility of root rot, and people should avoid soils with heavy clay that retain much water. They can use organic compost to break up clay-rich areas for better drainage.
• Sunlight Needs: Milkweed must be planted in a full-sun area with at least 6–8 hours of direct sun daily. Some species tolerate partial shade, but excess shade can prevent flowering and weaken the plant.
• Watering Practices: Milkweed is drought tolerant and, once established, needs little to no watering. Deep watering during prolonged dry spells is helpful to promote vigorous root growth. Do not give too much water to the succulents, as this can lead to fungal infections and root rot.

Planting Methods

There are two primary methods of planting milkweed, which are discussed here:

1. Direct Sowing

• The best time to do this is late fall or early spring, as milkweed seeds need cold stratification (a period of exposure to cold temperatures) to germinate successfully.
• Sprinkle seeds atop the dirt and cover thinly with ¼ inch of dirt.
• Light water is used to settle seeds, but it is not overwatered.

2. Transplanting Seedlings

• If starting indoors, sow seeds 6–8 weeks before the last frost.
• When transplanting, use peat pots or other biodegradable containers for less root disturbance.
• Seedlings can be taken outdoors once the temperature stays above 55°F (13°C).
• In the first several weeks, ensure young plants have lots of water.

Proper Spacing

The rule is to space milkweed plants 18 inches apart when planting for air circulation and growth. However, species like common milkweed (Asclepias syriaca) are aggressively spread by rhizomes, so spacing helps prevent overcrowding and unwanted spreading.

Propagation Techniques

Seed, cuttings, or natural self-seeding are the propagation methods for milkweed.

1. Growing from Seeds

Milkweed seeds will remain dormant not because they are sleepy but because they have a hard outer coating that requires cold stratification to break dormancy to germinate. Put seeds in a moist paper towel, put in a plastic bag, and stick in the fridge 30 days before planting. For outdoor use, plant seeds directly in the soil in late fall so that they naturally experience cold temperatures.

1. Pack seed trays or small pots with a fast-draining seed-starting mix.
2. Sow seeds ¼ inch deep and cover lightly with soil.
3. Keep the soil moist (not soggy) and place in a warm spot (65–75°F / 18–24°C).
4. Most seeds sprout in 10–14 days.

2. Propagating from Cuttings

However, if gardeners take cuttings to grow milkweed, it will grow much faster than if they had grown it from seeds. Here is how to break it down:

1. Choose a healthy green stem with at least two sets of leaves.
2. Cut 4–6 inches below a leaf node.
3. Strip the lower leaves, leaving the top set.
4. Dip the cut end in the rooting hormone to encourage the roots to grow.
5. Grow it in a container in a mix of perlite and peat moss.
6. Water so the soil is moist but not soggy and set in bright, indirect light.
7. When roots are well established, transplant outdoors.

3. Natural Propagation

Milkweed naturally spreads through wind-dispersed seeds attached to silky fibers (floss). To avoid overdoing it, pluck seed pods before they burst. If collecting seeds to replant, cover the pods with a mesh bag to catch them before they fly away.

Maintenance and Garden Integration

Once it’s established, milkweed doesn’t require much maintenance. With the proper care, these lush plants can grow to be hardy, flower-filled beauties that last years in the garden.

1. Minimal Fertilization

Milkweed doesn’t require much fertilizer and thrives in poor soils. During the blooming period, it needs organic, low-nitrogen fertilizer.

2. Pest Control

Milkweed is relatively pest-resistant, though some people report seeing some pests.

• Aphids: Microscopic yellow bugs that feast on plant sap. They can deter them by spraying the plants with water or adding natural predators, such as ladybugs.
• Milkweed Bugs: These orange-and-black bugs suck the seeds but typically don’t harm the plant. They can be restrained by hand-picking.
• Spider Mites: These minuscule bugs turn leaves yellow. Humidity around the plant should be increased to avoid infestations.

3. Managing Toxicity and Herbivores

Milkweed has cardiac glycosides, which can be toxic to many animals. Most deer and rabbits avoid eating it because it is bitter. Put up fencing or companion plants like strong-scented plants such as lavender to drive away herbivores.

4. Companion Planting

Milkweed pairs well with other pollinator-friendly plants to enhance the beauty and biodiversity of the garden.

• Coneflowers (Echinacea spp.): Supplies nectar to butterflies and bees.
• Black-eyed Susans (Rudbeckia hirta): Pair milkweed with cheery yellow blooms.
• Lavender (Lavandula spp.): Repels vermin and adds perfume.
• Bee Balm (Monarda spp.): Lures hummingbirds and butterflies.

Milkweed and Monarch Butterflies

Milkweed is vital to monarch survival since the plant and the butterfly share a special relationship. Understanding this relationship illustrates how crucial it is to protect milkweed and take measures to ensure monarchs' survival.

1. The Monarch-Milkweed Connection

Milkweed is the most crucial lifeline for monarchs, as it is the sole plant where they lay their eggs and where their caterpillars eat and grow. This is why monarchs need milkweed:

• Female monarchs will only lay their eggs on milkweed leaves because their caterpillars can eat nothing.
• Monarch caterpillars only eat milkweed leaves, which provide the nutrients they need to develop.
• Milkweed contains natural toxins, which monarch caterpillars ingest. These toxins render them toxic to most of their predators, including birds.
• Once they’re butterflies, monarchs drink nectar from milkweed flowers and other plants to get energy.

2. How Fewer Milkweed Plants Affect Monarchs

Over the past two decades, monarch populations have declined more than 80% in the eastern U.S. and died off 99% in the western U.S. Losing natural areas, farming, and tree cutting eliminated many milkweed plants. 

Agricultural weed killers (herbicides) have killed wild milkweed. Climate change has altered bloom times and disrupted monarch migration. Without more milkweed plants, monarch butterflies will continue to decline and could one day be at risk of endangerment.

3. How Milkweed Supports Monarchs Through Their Lifecycle

Milkweed hosts monarchs at every stage of life, from egg to adult.

• Female monarchs deposit tiny white eggs on the lower side of milkweed leaves so they are sheltered from inclement weather and predators.
• One female can lay hundreds of eggs, but very few become butterflies.
• And without sufficient milkweed plants, monarchs have no places to lay their eggs.
• Monarch caterpillars eat milkweed leaves as soon as they hatch to grow.
• Milkweed provides them with everything they need to grow.
• The caterpillars consume milkweed’s toxins, rendering them poisonous to most animals.
• The caterpillars grow sufficiently large in about two weeks to form a chrysalis.
• Robust caterpillars become robust butterflies, which require energy for migration.
• Monarchs migrate north from Mexico to North America each year, flying thousands of miles.
• In between, they require milkweed and other nectar-laden blooms to stay alive.

4. Efforts to Protect Monarchs and Milkweed

Because monarch populations have plunged, many nonprofits, scientists, and government groups are rebuilding milkweed's presence. People can also help by planting milkweed and avoiding harmful chemicals at home.

• Projects to Restore Milkweed

Organizations like the Monarch Joint Venture and the Xerces Society are increasing milkweed to provide safe habitats. U.S. Department of Agriculture (USDA) programs support farmers who grow milkweed on their land.

Some states have begun planting milkweed along highways to improve monarch habitat. Scientists are helping map out the best milkweed species to grow for various regions to help conserve these butterflies.

• How Gardeners Can Help

Plant native varieties of milkweed indigenous to the local area. Plant tropical milkweed (Asclepias curassavica) in mild environments, as it is known to confuse monarch migration cycles.

Don’t use pesticides and herbicides that could harm monarchs and other pollinators. Plant flowers rich in nectar and milkweed, which provides food for adult butterflies. Add shrubs and tall grasses for butterflies to find safe resting spots.

FAQs

What is milkweed good for?

Milkweed is a monarch butterfly necessity, offering food to caterpillars and nectar to pollinators. It also supports biodiversity and the restoration of ecosystems.

Is milkweed toxic to humans and animals?

Yes, milkweed contains cardiac glycosides, which can be toxic if ingested by humans, pets, or livestock. However, monarch caterpillars use these toxins as a defense against predators.

How does milkweed spread?

Milkweed spreads via wind-blown seeds and from underground rhizomes that send up new plants. Some species, such as common milkweed, can be aggressive growers.

The Bottom Line

Milkweed isn’t just a pretty plant; it’s crucial to monarch butterflies and many other pollinators. As natural habitats fall to development and weedy growth gets mowed, milkweed planted in gardens, parks, and wild areas can help protect these vital insect species.

Planting native milkweed and other plants for monarchs, staying away from chemicals that are harmful to them, and taking other steps, including conservation efforts, are easy ways to help the butterflies and the ecosystem. Check Growcycle to learn more about the best perennial plants to grow.

Disclaimer: This material is for informational purposes only and should not be relied on for legal, medical, financial, or any other form of professional advice.

About the Author

Victor Miller

Environmental Journalist Focused on Sustainable Agriculture

Victor Miller is an environmental journalist at Growcycle, specializing in sustainable agriculture. With a passion for storytelling, he highlights the latest trends, innovations, and practices that promote ecological balance and responsible farming.