Encouraging Monarch Butterfly Eggs in the Garden

Monarch butterfly egg close up on swan plant leaf

Hoping for monarch butterfly eggs on your swan plants? We’ve be working to make our garden a prime place for growing the next generation of monarch butterflies. In this post of our special monarch mini-series, we take a look at the reproduction through to egg-laying phase of monarch life, with ideas for encouraging monarch butterflies to visit and (hopefully!) lay eggs in your garden.

Setting the Scene with a Monarch-Friendly Garden

If you’re hoping for caterpillars, it all starts with getting a healthy mated female monarch to lay an egg. That requires available accessible swan plant (milkweed). It’s a homing beacon for monarch mommas! Keep it healthy and hydrated, spray-free, and visually check regularly to remove any pests or unhealthy growth.

The first post of this mini-series shared the details of planning and planting a monarch-friendly garden.  Check it out for details on our garden plantings, with a focus on the planting, positioning, and function of our separated milkweed plantings. 

Monarch Butterfly Mating Process

Once the scene is set, with any luck, somewhere in the neighbourhood there is a little monarch hanky-panky in progress. Monarchs mating isn’t something we get to see often, but you might be lucky enough to happen upon the right place at the right time (mating can last for hours!).

Like many butterflies, monarchs mate with their abdomens paired in opposite directions, as shown in my photo below. The female monarch collects and stores the sperm within her body until egg-laying time. Fertilisation occurs during laying, which allows control over timing whilst finding suitable sites to lay the eggs. Male monarchs may mate numerous times, but most females mate only once.

Monarch butterflies mating

The Search for Suitable Swan Plants (Milkweeed)

Female monarchs have a very important monarch momma mission to find swan plants (milkweed) on which to lay their eggs. Monarch caterpillars dine exclusively on milkweed, so it’s essential that eggs are laid on milkweed to provide immediate access to food. In our experience, their milkweed homing skills are amazing. It’s quite special to watch as they flutter about homing in on target lock. The more milkweed, the stronger the scent and attraction. 

On arrival, she will check the plant(s) for suitability by “tasting” it with sensors on her forelegs as seen in my photo below. Our NZ monarch migrations are short haul, but this momma was still a weary looking battler. Check out that taste test, though! She still has her monarch momma priorities straight.

Monarch butterfly tasting milkweed before laying eggs

Monarch Butterfly Egg Laying Process

Once the monarch is happy with suitability, she will lay individual eggs, fertilising each as she lays, before journeying on to other plants in the garden or elsewhere. The female grips the plant and touches the tip of her abdomen (the ovipositor) to the leaf and deposits a single egg.  The eggs are a creamy white colour, slightly ridged oblong shape, and around the size of a pinhead. See the macro photo at the start of this post. Monarch mommas are clever girls, and eggs are often (not always) positioned on the underside of a leaf where they have more shelter and are less visible to predators. 

Female monarch butterfly laying eggs on milkweed

The butterflies often flutter up and away from the plants between each lay, sometimes even stopping for a drink/snack, so having a butterfly-friendly garden area near the milkweed is very helpful.

A female monarch butterfly can lay hundreds of eggs.  By dispersing them individually and in many locations, her offspring will have a greater chance of survival. Only a fraction of the eggs laid in the wild (or in exposed gardens) will become butterflies. Many eggs, caterpillars, and chrysalides will succumb to predators, disease, weather, and other factors. You can encourage additional laying by catering for this natural instinct. Position plants in a variety of locations (e.g. dispersed in-ground positions or by dispersing mobile potted milkweed), and/or collaborate with neighbours for planting.

Monarch butterfly eggs on swan plant (milkweed)

From Egg to Baby Monarch Caterpillar

Once you have monarch butterfly eggs, the wait for the caterpillars begins. Hatching time varies with season and weather conditions, but as with all things butterfly, it’s brief. Hatching usually occurs after around 4-5 days in temperate weather.  Not all eggs will be viable/fertilised and, as mentioned above, not all will make it to the hatching stage, but such is nature’s way. 

In our garden, the plants which are available to butterflies are not netted; however, some people choose to net after eggs are laid to decrease potential losses. Others like to remove the eggs to raise in dedicated hatcheries or indoor areas. Whatever you choose, make sure you have enough swan plant (milkweed), because those babies will be hungry when they arrive!

Stay tuned for the next post of the mini-series, where I’ll introduce the babies and talk about life with hungry caterpillar garden guests.

Encouraging Monarch Butterfly Eggs in the Garden


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