Tips to Raise More Monarchs

More than ever before monarchs need our help. In North America deforestation, pesticide use, GM crops and climate change are affecting numbers. Monarch populations are struggling here in NZ too: they are ravaged by social wasps, their major predator.

Commercial growers raise thousands of swan plants (a species of milkweed). Plants need to be in the best condition to be sold. Garden centres cannot sell plants covered with aphids or bereft of leaves so some growers use pesticides to protect their plants until customers buy them.

Remember a female monarch can lay about 700 eggs (one was recorded as laying 1179!). The caterpillar grows almost 3000 times in size over two weeks. So one day there are lots of leaves… but a day later the plant is just a stalk.

Some garden centres will not sell plants with pesticide on them and will also be able to advise on nectar sources and host plants for native butterflies and moths. Always ask your garden centre, when checking out “is this plant safe for caterpillars?” If that person doesn’t know, ask them to find out. Garden centre staff should be aware of how safe the plants are.

As well, here are some additional tips on how you can raise more magnificent monarch butterflies.

  • Grow your own plants from seed – that way you will know for sure whether the leaves are safe for caterpillars. Buy seed anywhere you see Yates products. Yates gives the MBNZT a donation for each packet sold. Plant seed now for next year.

  • Grow plants on from previous years so that they are in their second season and over 1 metre tall. If they are fertilised, watered and mulched the growth in the spring and summer will almost keep up with the caterpillars.

  • When you buy plants, buy twice as many and protect some for next year’s monarchs.

  • Seedlings that pop up in the wrong place can be left until you need food. Cut it off and put it in a bucket of water, splitting the bottom of the stem before you do so it will better absorb water.

  • Caterpillars shed their skin five times. Do not disturb them when they are moulting. Observe the life cycle but minimise handling. Monarchs have been undergoing metamorphosis for hundreds of years without our help.

  • Pesticides such as fly sprays, plug-in insect controls and flea collars on pets will kill caterpillars. Sun-screen and cosmetics on hands can also affect them.

  • When your plant is 15-20cm tall pinch out the growing tip just above a node. The plant will now form two branches and bush out, creating twice as many leaves. A few weeks later pinch out the growing tip of the new branches. Also, a plant’s mission in life is to reproduce (set seed). Leaves feed caterpillars… flowers lead to seed. Removing flowers and the plant continues to strive to fulfil its mission and as a result will feed even more caterpillars.
  • If you introduce new plants let the caterpillars move themselves to the new plant. Put the new plant next to the old one or cut the stems with caterpillars on and put them at the base of the new plant.

  • Remember, swan plants and monarchs are poisonous so be careful when handling them. Monarchs store toxic steroids (known as cardenolides) from the swan plant and use them as a defence against some predators. The colour orange is a warning to say ‘I taste bad’.
  • There are different types of milkweed, of which swan plant is one. New plant(s) may not immediately appeal to your caterpillars. Water the new plant well to rehydrate it.

  • If you are in a cooler area think about growing Asclepias incarnata or swamp milkweed. The plant will grow from a rhizome in the second and ongoing years, and will sprout soon after the last frost. It has a sweet but subtle vanilla scent, is very quick-growing and is a very popular nectar source as well.