Caterpillar Care (Monarchs)

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    A monarch caterpillar will grow to 3,000 times its original size so it is going to eat a lot of milkweed (e.g. swan plant). Nobody wants their caterpillars to die so here are some key points to remember:

    Some people say three medium-sized plants per caterpillar are needed for the caterpillars to successfully pupate and for the plant to thrive.

    When buying plants buy twice as many as you think you will need and keep some protected for next year’s monarchs. At the same time plant plenty of seed(s) so that you have more plants growing. Do you live in a part of New Zealand where you have to get new plants each year, or do your plants need to be replaced each year? Then as soon as you can after winter get seeds sprouting and buy your swan plants. Plant them in a warm, sunny place. The monarchs won’t be far behind.

    If you are giving caterpillars away be careful about the container that you put them in. In plastic they will sweat and be stressed and that is where problems with disease will arise. If you can find a cardboard box this will be better. Also put in a framework of twigs (like a jungle gym) so that the caterpillars don’t all sit on the bottom of the box but climb around.

    There is some additional information HERE.

    If you want your butterflies to stay around your garden then we suggest you do the Create Butterfly Habitat Course to learn more about what they need.

Viewing 13 replies - 1 through 13 (of 13 total)
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    Hi Jacqui its Bron in Grey Lynn, could you please call me on 021 262 4344 urgently, i lost your number when my phone got nicked and i am desperately trying to find you, thanks



    I had to laugh when I read this, because of an experience I had. I was running short of milkweed plants for my cats, so I went to the local native plants nursery (I’m in Florida, USA) and bought 5 more plants. So far, so good; happy cats! Then I realized that the new plants were covered with eggs! Overnight, I went from 6 cats in my habitat to 17 and counting. I ended up beggin neighbors for more plants!



    Further to above, Here are a few photos taken recently of my patch in Christchurch.

    Barry P.



    Ha, the more plants of ANY asclepiad variety will feed more monarchs.
    The caterpillars are not fussy as to variety, but there are preferences when more than one variety is present.
    This animal is particularly food dependant and like rats with a ‘mast’ season, when the food runs out, so does the animal. This is very much the case with our Admirals and Nettle as well.
    Our focus needs to be on the food source, not the animal. In Christchurch it is difficult to have asclepiads available in any quantity for the first of Spring. ( I am working on that). Even so, a dense 2m x 1.2m patch barely 500mm high will be stripped bare in a couple of weeks by the 3rd generation, and there is the last cycle to yet begin!
    I have had so many butterflies this year and even more embarrassed by the chrysalis I now have with no prospect of food. My wintering over numbers will be really low as compared with a better plant management.
    So let us think more about food sources and quantity and the butterflies will arrive.
    Barry P. Shirley, Christchurch. 6.2.2020.



    Oh my goodness, then I urgently need to plant more swan plants – we have so many caterpillars because of our newly designed butterfly garden we made at the end of last year. Any suggestions where I could buy adult swan plants for cheap? We are a school that wanted to include the Monarch butterfly into our Environmental Science course this year, so we are still finding our feet.






    In Wellington I have 20 large caterpillars and 10 cocoons, but this year is different from others as the very strong, cold winds have reduced the number of caterpillars and blown some of the cocoons off the plants. Also the overwintering butterflies (there were 8 in the parkland behind me all winter) barely survived long enough to lay eggs. Thus I have caterpillars but there are no butterflies until the next generation emerges. This does not usually happen so late into the summer, so the window of opportunity to establish another generation after the winter has been very short.



    ALways ask if Mitre 10 or any garden center or supplier has sprayed the swan plants with fungicide, or pesticide, etc – as this will be toxic to Butterflies. Dont ask me how I know this 🙁 Fiona



    I own 6 swan plants have had 5 butterflies since getting them, as I write this I have 1 on my hand right now. I have moved at least 4 of my plants into our greenhouse to recover. I’m going to get more next time my local mitre 10 mega is selling them. They are beautiful and will be making a big monarch garden when I get my own place.


    yes thank you! I wish I’d know that before as we have run out of swan plants now. Is there anyone in Hamilton who has extra?



    Hi Lucy, So great of you having a swan plant and some caterpillars. You need several swan plants, one is not enough even for one caterpillar. Please make sure you check for eggs since your plants cannot support any further cats.

    Bunnings in Lyall Bay have them but with our poor summer you would many of them since they are not bushy or very tall. I live in Seatoun too. Caryl
    PS My private email is
    PPS Happy to answer your questions. Are you at Seatoun School?


    Lucy FL

    Hi Jacqui

    My name is Lucy. I am 7 years old And live in Seatoun in Wellington. My one swan plant has more than 15 2cm caterpillars. My one plant hasn’t many leaves left. What should I do to feed my caterpillars?

    Please can you give me some advice?

    Thank you,



    Thank you Jacqui for these useful tips – and some “Trade Secrets” too – for sucessfully caring for Monarch Caterpillars. The ratio of plants to caterpillars is one truly handy tip – amongst what is really A Survival Guide for Carers of Monarchs!! Thank you again – Best wishes Fiona

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