Butterfly garden autumn update

May 2026

With the shortening of the days everything in the butterfly garden has slowed, except perhaps for the slugs and snails. They move pretty fast when there are new seedlings to be chomped.

Unlike the start of May I now don't get to see butterflies before or after work, as the temperature or light levels are not high enough. I am sure I read somewhere that monarchs need it to be over 12.8 degrees to wake them from diapause, which is hibernation insect-style - literally a pause in their lifecycle.

There are still monarchs around in the middle of a sunny day. None of them are tagged - I do always check. It has been a fortnight since I saw a tagged monarch - one of my own returning - and it is hard to know what is going on without them as a reference. I am still getting eggs, which means there are butterflies who are completing their lifecycles. However, it really is getting chilly in Auckland now and the development of monarch caterpillars and chrysalis has slowed dramatically. Seeing how old the monarchs are that are in the garden would be really helpful and that's one of the things that reporting tagged butterflies offers. It's definitely the time of year to learn patience! Then again, if I was going to learn that lesson, I should have got it down by middle age.

A female monarch butterfly laying eggs on a swan plant in mid-May

The admirals are more resilient at the lower temperatures - eating me out of nettles again - and I have had a couple of yellow admirals emerge this week. I have adopted some red admiral caterpillars and the biggest of them are currently making chrysalis. I seem to remember from last year that they'll take around a month to eclose. A few weeks ago I caught a praying mantis cutting open the nettle tents and eating the caterpillars inside, so it is good that others have made it to pupa stage.

It is cold enough now that the vespula wasps have gone, but paper wasps are still around in low numbers. The cooler weather can mean they are slower than during summer, but so am I. I am missing as many as I kill. I am really suspicious that despite the monarch eggs that are still being laid, I am only seeing caterpillars on one particular swan plant. Something is taking them. Currently my garden boasts a grand total of one monarch caterpillar.

It is no surprise then that I broke my promise to leave the monarchs alone and have brought eggs in to raise. I want to have adults to tag and I have another 20 tags to go, so I'll keep interfering for now. It is not all sunshine and roses for the ones I have taken in from the garden, because they have to go back outside into the protection of the plant cage or caterpillar castles for the later instars. I notice a takeaway container I put out earlier this week with the lid half off, still has the caterpillars inside, rather than them having transferred to the fresh plant. I imagine it is a little bit like a warm greenhouse, even if the leaves inside are days old. I wouldn't normally leave the lid, but there was a caterpillar contemplating shedding its skin between instars on it and it was important not to disturb it.

The only good thing about the cool weather is that the leaves on the liquidambers changed colour to yellow and reds (beautiful) and most of them have now fallen. This means the low sun can get to the main bed in the butterfly garden once again. It is still shady for a lot longer than in summer, but there are a fair number of flowers out. The tree dahlias are a joy and the first flowers on the Tagetes lemmonii, a shrub marigold, are out. Both were from the MBNZT cuttings sale last year. I've planted some seedlings from Mitre 10 to add to the flowers through winter, but I think there will be enough blooming. Last year the ageratums and single camellias bloomed through all the winter months, bless 'em.

Tree dahlias, ageratum and Mexican bush sage providing May nectar in a sunny corner of the butterfly garden

In traditional gardener fashion, I am using the cool months to have a re-think of the butterfly garden beds so there is more consideration to its aesthetic qualities. If you read my earlier posts, you'll know the design of the butterfly garden gave me such a headache I just had to let it go and instead just see what happened. It's definitely been a success as a butterfly and pollinator space, but it looks bitty. Having a better idea now what plants the butterflies enjoyed means I can add more plants that worked and remove plants that didn't. The bees are not fussy so they won't mind too much. I'll keep all their favourite salvias. Whilst insects are not fans of neat and tidy gardens, I think the current fashion for naturalistic planting schemes are the best of both worlds - attractive to us, but just scruffy and varied enough for wildlife. How I achieve that is still a mystery, but I've got some time to think about it.

I am genuinely thinking of pulling some of the swan plants out. If they can never safely host a generation of monarchs in autumn or spring, then they are not serving much purpose other than looking ugly. Fortunately I like the look of tropical milkweed, which has more interesting foliage and is the favourite flower of the monarchs so I'll plant more of those instead. Unfortunately the swan plant that is most conspicuous by the entrance to our property is the one that the caterpillars seem to survive on, at least for a time. Oh well, that one will have to stay for now. I might go back to the trick from the old house: Putting potted swan plants out for the females to lay eggs on, then putting them somewhere protected until the butterflies emerge. Again, I've got time to think about it. Despite all the work last winter to get the butterfly garden expanded, I am very much a fair weather gardener, so as the butterflies slow, so will I.