March is the month when we become aware that the days are shortening and night temperatures cooling but autumn? Not yet, at least not in North Taranaki where we drift ever so slowly from season to season. But every year, the same pressure comes on – the plight of the monarch butterflies.March is the start of the critical period. We have monarchs on the wing twelve months of the year in our garden. To a large extent, that is because we take active steps to guard the late season caterpillars. These are the ones that will chrysalis and hatch out as conditions for them grow more difficult. Given the short life span of a monarch butterfly – usually only a month, the internet tells me – it is these late season candidates which will winter over and guarantee continuance through next summer.
In North America monarchs migrate vast distances to over-winter in the mountains of Mexico but our monarchs are not as determined and will stay at home. Occasionally we find a tree where many are clustered together and it is truly a small wonder in our world to see them stretching and flexing their wings in what little warmth there is on a sunny winter’s morning. More often, we will see raggedy specimens bravely feeding from seasonal plants. The so-called Edgeworthia papyrifera (yellow daphne) can be an astounding sight in August. The key to keeping our monarchs close to home is year-round food supplies, which means plenty of flowers with visible stamens and pollen which are a fair indicator of available nectar.
No doubt many readers are currently suffering the seasonal anxiety of stripped swan plants and a surfeit of caterpillars at all stages of development. The caterpillars are very selective about food sources. Basically they need swan plants. We always knew these as Asclepias fruticosa but I see they have now been reclassified as Gomphocarpus fruticosus for the common one and G. physocarpus for the giant swan plant and I can’t commit either of those names to my memory. You can – and we have in the past – get medium and large caterpillars to chrysalis-size on slices of pumpkin but you have to confine them because they will head off looking for their preferred food source given the opportunity. Is there anything as brave as the sight of a procession of monarch caterpillars heading away in search of more food?
Nowadays we try and reserve plants for late season caterpillars, covering them with netting and taking steps to rid them of the nasty yellow aphid that can decimate the plants. There is a specific aphid spray that does not harm the caterpillars when infestations are really bad. Both Yates and Tui have organic products that target mites, whitefly and aphids. Later in the season, Mark will start his chrysalis rescue programme, carefully tying them with cotton to suspend them safely because they can rarely hatch successfully if lying on the ground.
We are finally getting patches of stinging nettle established. The only reason for this is to encourage the admirals, both red and yellow, to move into our garden. It is not our large native tree nettle – Urtica ferox – but one of the dwarf ones which has turned up which we are allowing to stay. Unlike the monarchs, which are self-introduced to this country and were first recorded around 1840, our brand of red admirals are truly indigenous and not found anywhere else in the world. Because their host plant is not as obliging and hospitable as the monarch’s swan plant, they need all the help we can give them. That said, there was a news item that came through at the start of this year reporting that the US Fish and Wildlife Service is taking steps to protect the monarch butterfly under the Endangered Species Act. Loss of habitat and modern farming methods have caused a massive drop in the monarch population and there are fears that, without intervention, they may die out.
Some utilitarians may ask what useful contribution butterflies make to human life. It is true that there their direct contribution does not equal that of bees. But as gardeners, most of us set out to cultivate transient and ephemeral blooms for no other reason than that they are beautiful and bring delight. Butterflies are beauties of the insect world and their continued presence is a good indicator of a healthy ecosystem.
New Zealand has an active Monarch Butterfly Trust with a comprehensive website. While the obliging monarch is their main focus, they cover the whole range of butterflies found in New Zealand (which is not large by international standards) and they touch on the moths (which are considerably more numerous here but less appealing to most people). You will find answers to many specific problems on that site. While the obliging monarch is their main focus, the site has information on a whole range of butterflies found in New Zealand, which is not large by international standards, and they touch on the moths, which are considerably more numerous here…but perhaps less appealing to most people.
First published in March issue of New Zealand Gardener magazine and reprinted here with their permission.