Monarch Butterflies

– Encouraging the Population
– Caring for the Caterpillars

Monarch butterflies might just be a pretty sight, but are actually a beneficial pollinator for the garden. It’s a wonderful idea to encourage them to flock to your garden, and give them a helping hand to replenish the new generation.

Favourite flowers of the Monarch are Cosmos, Asters, Echinacea (coneflowers), Dandelion, Lonicera (Honeysuckle), Lilacs, Buddleia (butterfly bush), and many more! Planting a fragrant, colourful, nectar-rich garden will attract plenty of butterflies. Herbs such as catmint, bee balm, and basil are well loved, as well as any and all types of Milkweed of course! Did you know Monarch butterflies can smell Swan plants from up to a kilometre away?

An egg takes about 7-10 days to hatch. The caterpillar phase takes 10-14 days and the chrysalis phase then takes another 10-14 days. These cycles slow down in cooler weather. When a chrysalis is about to hatch, it goes transparent so you can see the colour of the butterfly wings showing through. It then can emerge quite quickly (from as little as 20 minutes) into a beautiful monarch butterfly.

The Monarch butterfly season typically runs from September to March. We stock Swan plants at the Garden Centre during the season (October to March). As well as seed stock year round. We highly recommend sowing seeds early, covering with a bug net, and allowing the plants to mature before the breeding season begins. This will ensure a good supply of food is available for the caterpillars.

According to the official Monarch website (www.monarch.org.nz) baby caterpillars need to feed off the swan plant (Gomphocarpus fruticosus) or the giant swan plant (G. physocarpus). They also eat the Asclepsias species such as tropical milkweed/bloodflower (A. curassavica). Monarch caterpillars/butterflies are poisonous to predators and they get this toxicity from eating the poisonous milkweed. 

Caterpillars are voracious feeders and just a few will very quickly eat through a whole plant, often depleting their food supply before they’ve hit the chrysalis stage. Causing gardeners to run to the store to source fresh swan plants, or find a new food source.
Unfortunately, there are no other safe food options available for feeding caterpillars. A common solution has been to grow the caterpillars on pumpkin or kapok plant in their final stage. Studies show that this will often lead to deformities in the mature butterflies, so these are not suitable food sources.

Some people have problems with wasps killing monarch caterpillars. Wasps lay their eggs on the caterpillars and the wasp larvae kill the caterpillar by eating it. To protect against wasps, try covering the swan plant with a mosquito net or something with a small weave. This will also prevent further monarch eggs being laid and depleting the food resource even more.

Aphids can also be a problem on swan plants and it’s challenging to find an effective treatment that eliminates aphids without harming the Monarch caterpillars. No solution is fool-proof, but here are some you can try:

• Cover the plants with a bug net to prevent pest insects from accessing your plants.
• Attract the natural predator, Ladybirds, to your garden by planting herbs such as dill, yarrow, cilantro, chives, & marigold nearby.
• Manually remove the aphids and gently wash with a soapy water.
• Spot spray for aphids using Enspray 99 oil. Take great care not to spray any caterpillars directly. You may want to rinse the plant off a little time after spraying and allowing the aphids to be treated.