The New Zealand Red Admiral Butterfly, (Bassaris gonerilla or kahukura), is endemic to New Zealand, which means it is not found naturally anywhere else in the world. In 1928 the Red Admiral butterfly was described as “very common”, but it would probably not be described that way today. A number of reasons have been suggested for its decline such as the parasite wasps Echthromorpha intricatoria that came here from Australia in the 1900s, and Pteromalus puparum, which was deliberately introduced in 1933 to control the Cabbage White Butterfly.
Another possible reason is a reduction in the availability of their food plants. The preferred food plant of the Red Admiral caterpillar is Urtica ferox (ongaonga or tree nettle). The caterpillars also feed on other nettles such as Urtica incisa (scrub nettle), Urtica aspera and Urtica urens (Dwarf Nettle).
The Nettle family are also host plants for the Yellow Admiral caterpillars. There are many kinds of Nettles, with Wikipedia estimating 30-45 species, although not every plant with nettle in the name is from the nettle family, Urtica. Nettles have a long history in folklore, with a lot of myths surrounding them as well as a confusing variety of different names for each species. So for example Urtica dioica has also been referred to as U. breweri, U. californica, U. cardiophylla, U. lyalli, U. major, U. procera, U. serra, U. strigosissima, U. trachycarpa, and U. viridis. It is most often called common nettle or stinging nettle, but also goes by the names tall nettle, slender nettle, California nettle, jaggy nettle, burning weed, fire weed and is one of the three different kinds of plant known as bull nettle.
So the following is intended to be a helpful introduction, not an exhaustive list!
Also known as Common nettle or stinging nettle. It is a native of Europe, Asia, North America, and North Africa. It is a Perennial growing 1 to 2 m high, with leaves 3 to 15 cm long. wikipedia.org, New Zealand Flora
Also known as Dwarf Nettle. It is a native of Europe and North America. It is an annual growing about ½ m high, with leaves up to 8cm long. wikipedia.org, New Zealand Flora
Also known as Ongaonga or tree nettle. It is endemic to New Zealand. It is a perennial growing up to 5m high. Ferox is Latin for ‘fierce’ and a hunter once died after pushing through a dense patch of it. wikipedia.org, http://www.nzpcn.org.nz, Oratia Native Plant Nursery, Flora of New Zealand
Also known as Pureora or scrub nettle. It is native to New Zealand and SE Australia. Height variously reported between 40cm and 2m. Leaves 5-12 cm. Likes shade or mild sun and a sheltered spot. wikipedia.org, nzpcn.org.nz, Oratia Native Plant Nursery, nzpcn.org.nz, Flora of New Zealand
Also known as Southern nettle. Native to Chatham and Stewart Islands. It grows up to 1m tall with dark green leaves, 10-15 cm by 8-14cm. nzpcn.org.nz, Oratia Native Plant Nursery, Flora of New Zealand
This is an uncommon nettle from the South Island. It grows to ½ m high with leaves 2-4cm long. It prefers dry and shady conditions. nzpcn.org.nz, Flora of New Zealand
(Occasionally referred to as Urtica debilis) Also known as New Zealand pellitory although it is found throughout the Southern Hemisphere. A spreading annual plant forming patches up to 50cm diameter. It has the advantage over other Admiral host plants of not having a sting, however its small leaves make it less than ideal. wikipedia.org, nzpcn.org.nz, Oratia Native Plant Nursery, Flora of New Zealand
Children and Nettles
Unfortunately Nettles are listed in “Safety in pre-school centres: plants to avoid” (http://www.landcareresearch.co.nz/__data/assets/pdf_file/0011/42014/preschool.pdf) so simply planting them in your children’s butterfly garden is a no-no if you are a pre-school. However there are still a number of options for making Red and Yellow admirals part of a butterfly garden for children.
The easiest option is stick to the stingless Parietaria debilis and accept that it will not be able to support many caterpillars. Another option would be to plant the nettles behind a fence or barrier so the children can see them but can’t touch. Alternatively grow the nettles in hanging baskets out of their reach. Perhaps combine those options by placing Parietaria debilis where they can have a close look, but have the main supply of nettles elsewhere. For a butterfly garden in a home another option is to accept that a nettle sting is something they will get over, and they will treat nettles with more caution in future.
Phenology and parasitism of the red admiral butterfly Bassaris gonerilla. New Zealand Journal of Ecology (2004) 28(1): 105-111, downloaded from http://www.nzes.org.nz/nzje/free_issues/NZJEcol28_1_105.pdf
Moore, L.B.; Edgar, E. (1970) Flora of New Zealand. First electronic edition, Landcare Research, June 2004. Transcr. A.D. Wilton and I.M.L. Andres. http://FloraSeries.LandcareResearch.co.nz