Do Monarchs Lay Eggs on Butterfly Weed? Unveiling the Truth
The short answer is yes, but only indirectly. Monarch butterflies don’t lay eggs directly on butterfly weed (Asclepias tuberosa). However, butterfly weed is a species of milkweed, and all species of milkweed are the sole host plant for monarch caterpillars.
Milkweed: The Lifeblood of Monarchs
Monarch butterflies are arguably one of the most recognizable insects in North America, famous for their vibrant orange and black wings and epic migrations. But their survival hinges on a single, crucial element: milkweed. Monarch caterpillars exclusively feed on milkweed leaves. Without milkweed, monarchs cannot complete their life cycle.
Why “Butterfly Weed” is Confusing
The term “butterfly weed” can be misleading because it’s a common name for Asclepias tuberosa. Asclepias tuberosa is visually quite different from other milkweed species, such as common milkweed (Asclepias syriaca). Its brilliant orange flowers attract many butterflies, hence the name. However, it’s the milkweed aspect that matters to monarch butterflies looking for a place to lay their eggs. The Asclepias genus is critical.
Milkweed Selection: More Than Just a Plant
Monarchs don’t simply lay eggs on any milkweed they find. They are selective, and a variety of factors influence their choice:
- Plant Health: Monarchs prefer healthy milkweed plants. These plants provide more nutritious leaves for their caterpillars.
- Plant Age: Younger, tender leaves are often favored over older, tougher ones.
- Sunlight Exposure: Milkweed plants in sunny locations tend to be more attractive.
- Predator Presence: Monarchs try to avoid laying eggs on plants already harboring predators such as aphids, spiders, or milkweed bugs.
- Milkweed Species: While monarchs will use a wide variety of Asclepias species, some species may be preferred in certain regions due to their availability and suitability.
The Egg-Laying Process
The monarch butterfly’s egg-laying process is a delicate and strategic undertaking:
- Searching: The female monarch flies through milkweed patches, carefully inspecting plants.
- Tasting: She uses sensors on her feet to “taste” the leaf surface, determining if it’s a suitable host plant.
- Laying: If satisfied, she curls her abdomen and attaches a single, tiny, pale-yellow egg to the underside of a leaf. She rarely lays multiple eggs on the same leaf.
- Repeating: The female will then move on to another plant to repeat the process, dispersing her eggs to reduce competition among the caterpillars.
Common Mistakes in Milkweed Gardening
Many gardeners, even those with good intentions, make common mistakes when trying to attract monarchs:
- Using Pesticides: Insecticides, even those marketed as “butterfly-friendly,” can harm or kill monarch caterpillars and eggs.
- Planting Only Butterfly Bush: Butterfly bush (Buddleja davidii) attracts adult butterflies but is not a host plant for their caterpillars. Plant milkweed in addition to butterfly bush.
- Overcrowding Milkweed: Give milkweed plants ample space to grow. Overcrowding can lead to diseases and pest infestations.
- Not Providing Enough Sunlight: Milkweed requires at least six hours of direct sunlight per day.
- Planting Only One Species: Providing a variety of milkweed species can attract more monarchs and offer resilience against localized plant diseases.
Milkweed Varieties: A Comparative Table
| Species | Common Name | Flower Color | Hardiness Zones | Native Range | Notes |
|---|---|---|---|---|---|
| Asclepias tuberosa | Butterfly Weed | Orange (often yellow) | 3-9 | Eastern & Central US | Drought-tolerant; not preferred by caterpillars as much as others. |
| Asclepias syriaca | Common Milkweed | Pink | 3-8 | Eastern & Central US | Spreads aggressively; fragrant flowers. |
| Asclepias incarnata | Swamp Milkweed | Pink/Purple | 3-9 | Eastern US | Prefers moist soil; attractive to many pollinators. |
| Asclepias viridis | Green Antelopehorn | Green/White | 4-9 | Southern & Central US | Tolerates drier conditions; unusual flower structure. |
| Asclepias fascicularis | Narrowleaf Milkweed | White/Pink | 7-10 | Western US | Drought-tolerant; important for western monarch populations. |
Frequently Asked Questions (FAQs)
Are all milkweed species equally attractive to monarchs?
No, not all milkweed species are equally attractive to monarchs. Factors like leaf texture, the presence of toxins, and regional availability influence which species monarchs prefer. Asclepias syriaca (Common Milkweed) is often a popular choice where it’s native, while Asclepias curassavica (Tropical Milkweed) is widely planted but can harbor parasites if not properly managed.
How can I tell if my milkweed has monarch eggs on it?
Monarch eggs are tiny, about the size of a pinhead, and pale yellow or cream-colored. They are typically laid singly on the underside of milkweed leaves, especially near the top of the plant. A magnifying glass can be helpful for spotting them.
What should I do if I find monarch eggs or caterpillars on my milkweed?
Do not disturb them! Allow them to develop naturally. Ensure the milkweed has adequate water and sunlight. Avoid using any pesticides in the area. Consider protecting the plants from predators with netting if you are concerned.
Can I grow milkweed in containers?
Yes, some milkweed species can be successfully grown in containers. Choose a larger pot (at least 12 inches in diameter) and use well-draining potting mix. Asclepias tuberosa and Asclepias incarnata are good options for container gardening.
Is it safe to bring monarch caterpillars indoors?
Bringing monarch caterpillars indoors can be done, but it requires careful attention. You must provide them with fresh milkweed daily and maintain a clean environment to prevent disease. It’s generally best to let them develop naturally outdoors, if possible.
How long does it take for a monarch egg to hatch?
Monarch eggs typically hatch in 3-8 days, depending on temperature.
What do monarch caterpillars eat besides milkweed?
Nothing. Monarch caterpillars exclusively feed on milkweed leaves. No other plant can sustain them.
Can I move monarch eggs or caterpillars to a different milkweed plant?
Moving monarch eggs or caterpillars should be done with caution. If you must move them, do so gently, preferably to another milkweed plant of the same species. Avoid handling them excessively.
What are common predators of monarch caterpillars?
Common predators of monarch caterpillars include birds, spiders, wasps, ants, and milkweed bugs. Parasitic flies and wasps also lay eggs on caterpillars, which can eventually kill them.
How can I protect my milkweed plants from pests?
Encourage beneficial insects, such as ladybugs and lacewings, which prey on aphids. Hand-pick off larger pests, such as milkweed bugs. Avoid using broad-spectrum pesticides, which can harm beneficial insects and monarch caterpillars.
Is it necessary to cut back milkweed in the fall?
Whether or not to cut back milkweed in the fall is a matter of some debate. Cutting it back can help remove overwintering parasites on Tropical Milkweed (Asclepias curassavica). However, leaving other species standing provides habitat for beneficial insects and may allow for some late-season monarch breeding.
Where can I buy milkweed plants?
Milkweed plants are available at many local nurseries and garden centers, particularly those specializing in native plants. You can also find them online from reputable growers. Choose native milkweed species for your region to support the local monarch population.