Butterflies sustain themselves with nectar, which is why the first way to attract them to your garden is with a food source – namely flowers, and the more the merrier!
They are not fussy as to colour, but have a preference for short, tubular-shaped flowers that they can sip from easily with their flexible straw-like tongues (probosces), and have broad petals or a cluster of blooms to support them while they feed. There are all sorts of flowers that fit the bill. Some examples are annuals like cosmos, strawflower and zinnia, perennial gaillardia, purple verbena (Verbena bonariensis) and valerian, as well as shrubs such as Viburnum tinus, bottlebrush and native koromiko (Veronica speciosa).
Butterflies detect sources of nectar (or host plants) from a long distance away using “smell” – actually, chemoreceptors located on their antennae. Once they get closer they identify the plants by sight then land and “taste” them with chemoreceptors on their feet. Whether the style of your garden is natural and wild, carefully manicured plots or even pots on a balcony is of no consequence to a butterfly, but planting groups with a minimum of three or four of one type of flower or host plant helps it to home in on them.
Depending on the species, butterflies overwinter as eggs, caterpillars or chrysalises, or hibernate as adults (sometimes a combination of ways), so while they are most numerous in summer and autumn those that emerge from chrysalises in spring (e.g. coppers) or come out of hibernation to lay the first eggs of the season (such as monarchs) are well in need of spring flowers. Cineraria, cornflowers, statice and wildflower mixes are a few that can be planted to welcome the early arrivals.
Butterflies that hibernate can still be seen flying on sunny winter days and appreciate a ready source of nectar, too. Marguerite daisies, wallflowers, camellia, calendula and Buddleja auriculata are possibilities here.
A good way to judge what to plant is to walk around your local area and look at what is flowering well in the different seasons, then observe which of the flowers prove most popular with your butterfly visitors and increase the number of those.
If you want them to stay in your garden rather than just eat and run, the next step is to provide host plants. While the same flowers suit a large range of species each has a different and specific requirement for the plant they lay their eggs on, and some are easier to cater for in the home garden than others.
New Zealand has around 23 species of butterfly. Many of the endemic (i.e. found only NZ) ones, in particular, are confined to small areas, so some research might be needed to see which ones you could potentially attract.
The fat, bright yellow, black and white caterpillars of monarch butterflies feed on milkweeds. Swan plant (Gomphocarpus physocarpus) is a readily available and easy to grow type.New Zealand’s most common butterfly (as its name suggests) is the common blue, but it is easily overlooked because it is a small, grey/ blue butterfly that flies close to the ground. Its host plants are legumes, such as clover, lupins and peas. Their caterpillars, which look like tiny, green slugs, feed inside the flower buds and seed pods of their host plant and that is where they form their chrysalises, too. They are less common in our cities than they used to be and one reason for this is the close-cropping of lawns that sees the clover heads cut before the butterfly can complete its life cycle. To bring back these butterflies, plant patches of clover (decorative red and crimson is an option) and raise the level of your lawnmower.
The black and white magpie moth has a distinctive caterpillar with a shiny, black body, covered in long fine hairs, with a bright orange stripe running its length. I include the magpie moth here because it is day flying. One of its host plants is cineraria.
Yellow admiral caterpillars eat all varieties of nettle, both introduced and native, but prefer the exotic variety, Urtica dioica. They feed inside a tent of leaves, sewn together with silk strands, for protection.
Our variety of red admiral butterfly is found only in New Zealand. Because its natural habitat is forest and it lays its eggs exclusively on native nettles it is seldom seen in suburban gardens.
The host plants for copper butterflies, also endemic, are Muehlenbeckia complexa, M. australis (both of which can become rampant vines) and M. axillaris. The smaller ground cover, M. axillaris, is more manageable in the home garden, but since most copper butterflies don’t fly more than 50m from their host plants, unless there are already coppers in wild habitats or revegetation projects in your area you may not see them. However, all would not be lost because muehlenbeckia provides berries and cover for lizards, too.
If you’re lucky you might even attract some of the butterflies like painted ladies or blue moons that blow across from Australia each summer.
All caterpillars are voracious eaters, but unlike their parents they can’t travel far to look for food, so the more host plants you plant the better. However, no matter how much you provide, the caterpillars will usually eat more and your choice becomes to let nature take its course or protect some plants with netting to introduce later in the season.
Avoid using insecticidal sprays in your garden as these affect butterflies and caterpillars (not to mention bees and other beneficial insects) as much as the pests. The biological control agent, DiPel, which contains Bacillus thuringiensis, is non-selective as well and will kill most other caterpillars along with the intended pest species.
Another key criterion for a butterfly garden is to locate it in a sunny, sheltered area. Like other insects, butterflies are cold-blooded and need the warmth of the sun to be able to fly. A good-sized rock or two added to your garden in a sunny spot will absorb the sun’s heat and provide a place to bask, but I must admit the butterflies in my garden seem to prefer my clothesline.
Fighting against the wind to feed or lay eggs takes a lot of energy. Strong winds can blow caterpillars off their host plants – they are particularly vulnerable to falling when forming their chrysalises and hatching out of them – and can cause the wings of newly emerged butterflies to dry crookedly, so it makes sense to site your butterfly plants in a sheltered part of your garden.
In the wild, males can be seen drinking at the edge of muddy puddles or damp sand banks. This behaviour is called puddling, which is done to take in sodium and nitrates that are particularly important for reproduction. In the home garden, you can provide for your visitors by making a slurry of mud, sand and animal or chicken manure, and watering it to keep it damp during dry weather.
The final feature of the ideal butterfly garden is a tree (at least somewhere in proximity) to provide shelter at night and in wet weather, as well as a place for butterflies to overwinter.