Orange Tip Butterflies
Encouraging Orange Tip Butterflies in Your Garden
by Kiri Stuart-Clarke
Although not red-listed nationally, Orange-tips, Anthocharis cardamines, like most butterflies do need help in the face of climate change and habitat loss. From my 8-year casual recordings numbers are down, at least at my end of Mileham village.
A lot of people don't realise that Orange-tips use Garlic Mustard, Alliaria petiolata (also known as Hedge Garlic or Jack-by-the-hedge) and usually associate them with Cuckoo Flower, Cardamine pratensis, instead. Unfortunately this means that Garlic Mustard is often innocently pulled up as a "weed" just after egg-laying time, which is a shame as it has also got very attractive foliage I think and looks good against a south facing wall.
Gardeners can help Orange-tips in two ways. Firstly by checking over any Garlic Mustard they need to weed out for butterfly eggs and relocating the eggs to a safe alternative host plant and secondly by proactively growing the host plant in a suitable spot.
Growing Orange-tip Host Plants
Garlic Mustard is very easy to grow from seed in autumn or young plants from online wildflower providers like Naturescape in spring. (Other native plant suppliers exist, do order early to catch egg laying season).
You will need to grow a generous clump in a sunny area (The butterflies don't oviposit on shady clumps) and leave the plants all year as many, though not all, caterpillars stay and pupate on the plants. Keep an eye out for ovipositing females and then look for the orange eggs regularly. They are pale yellow day 1, go bright orange on day 2 then turn dull brown a day or two before hatching after about 7 days).
If you have grown Garlic Mustard in pots then you can optionally check over the flower heads and buds for predators (moneyspiders and their fine webs, aphids and ladybird were all intentionally lurking in wait for mine), evict the predators and transfer the pots into a netted butterfly habitat to reduce predation (90cm ones can be ordered online for about £15 from places like Amazon or Bugzarre).
Growing Garlic Mustard can actually help two spring butterfly species, as it is also the caterpillar host plant for another white spring butterfly, the Green-veined White. The caterpillars however are not in competition with each other as the Green-veined White caterpillars eat the leaves of the plant whereas the Orange-tips feed on the seed pods.
You can also grow Cuckoo flower, Orange-tip butterflies’ other primary host plant, if you have a pond margin or bog garden of course. Orange-tips will occasionally lay on other crucifer wildflowers such as Charlock as well as Dames Violet and Honesty but larval survival is generally considered poor on these plants.
Transferring Eggs when Weeding
If you do need to weed out a patch of Garlic Mustard then it would be great if you can first check the undersides of the flower buds and bracts for eggs which are usually proud and quite visible and, if you find any, either pot up the plant, move and look after it. Otherwise clip the section with the egg on and then tie it as close to the flower tip bracts as possible onto another plant that is without an egg and that will be left in situ (or if wild, definitely won't be strimmed in road verge management). Tie the section securely, but without damaging the host plant stem, using fine wire or a non-fibre-shedding thread. The caterpillars are so miniscule on hatching they can even get caught in microfibres from polycotton just as in a fine spider web.
Lastly, its important to only put one egg onto each plant, or at least each flower head stem if the plant is a large second year one. This is because the Orange-tip caterpillars are opportunistic cannibals and will eat each other if they cross paths.
About the Author
I’ve been passionate about wildlife since I was knee high to a grasshopper and have been cultivating my garden as a space for wildlife ever since I moved to Mileham 8 or so years ago. I also currently volunteer for Norfolk butterfly conservation branch. If you have any questions, you can contact me via my longstanding nature photography blog www.kiri.uk (some of the articles there may be of interest) or the small wildlife and conservation gardening group I run on Facebook.
Wing undersides on both males and females have a green mottled pattern.Image by Kiri Stuart-Clarke
Garlic mustard (Alliaria petiolata), also known as 'Jack-by-the-hedge'
A female laying eggs (ovipositing)Image by Kiri Stuart-Clarke
A single orange tip eggImage by Kiri Stuart-Clarke
Close-up of an orange tip eggImage by Kiri Stuart-Clark
A newly-hatched caterpillar (first instar larva)Image by Kiri Stuart-Clark