Plants

This page is also available for download in pdf format: a-beginners-guide-to-nettles.pdf

The red admiral, (Bassaris gonerilla or kahukura), is endemic to NZ, which means it is not found naturally anywhere else in the world. In 1928 the red admiral butterfly was described as ‘very common’, but not so today. A number of reasons have been suggested for its decline such as the parasitic wasps Echthromorpha intricatoria that arrived 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 U. ferox (ongaonga or tree nettle). The caterpillars also feed on other nettles such as U. incisa (scrub nettle), U. aspera and U. urens (Dwarf Nettle).

The nettle family is also the host for the yellow admiral.

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!

Urtica dioica
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

Urtica urens
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

Urtica ferox
Also known as ongaonga or tree nettle, it is endemic to NZ. 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, www.nzpcn.org.nz, Oratia Native Plant Nursery, Flora of New Zealand

Urtica incisa
Also known as pureora or scrub nettle. It is native to NZ 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,

Urtica linearifolia
Also known as swamp nettle and creeping nettle. It is native to NZ. It grows up to 2m tall with narrow leaves 3-8cm long.nzpcn.org.nz, Flora of New Zealand

Urtica australis
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

Urtica aspera
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

Parietaria debilis
(Occasionally referred to as Urtica debilis) Also known as NZ 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/publications/infosheets/poisonplants/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.

References

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

https://www.monarch.org.nz/other-species/red-admiral-%E2%80%93-bassaris-gonerilla-kahukura/

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.

Urtica ferox (Tree nettle) poisoning

Seven Sharp with Hopeseeds.nz

Poisoned monarch caterpillars?

More than ever before monarchs need our help. As well as the shocking statistics coming from North America, where deforestation, pesticide use, GM crops and climate change are affecting the migration, the monarchs are suffering here. In this country they have been ravaged over the last two seasons by wasps, their major predator. Warm winters here in 2013 and 2014 have meant more social wasps. Hopefully this past winter has been colder and their numbers have been reduced; if this is so, there will be more hungry monarch caterpillars than ever.

The relationship between monarchs and milkweed (such as swan plants) is fascinating. Consider the predators, parasites and pathogens that affect monarchs. If people loved swan plants as they do rose-bushes, then we would see the monarch as a pest!

It is not a simple exercise for a commercial operation to grow swan plants. The plants need to be in a good condition when they go on sale. The two main challenges are monarchs and aphids. After all garden centres won’t want to sell plants that are covered with aphids or are bereft of leaves.

Some growers resort to using pesticides. Hopefully they don’t release their plants for sale until the chemicals are no longer active.

A female monarch lays on average of 700 eggs (one was recorded as laying 1179 eggs). After the caterpillar emerges from its egg it will grow almost 3000 times in size over the following two weeks. So one day you have lots of leaves, a week later and the plants can just be leafless stalks.

If you grow your own plants from seed you will know for certain that the leaves are safe for caterpillars. We encourage everyone to hold plants over from previous years. When a plant is over 1.5 metres in height, and if it is well fertilised and kept healthy, the growth in the spring and summer will almost keep up with the caterpillars.

So if you haven’t bought your plants this year, get twice as many and protect some for next year’s monarchs. Also get some seed – Yates gives the MBNZT a donation for each packet sold – and grow more plants. If seedlings sprout up in inconvenient places leave them until you need food. Pull out the plant, or cut it off at the stem and put it in a bucket of water, splitting the bottom of the stem before you do so it will better absorb water.

Here are some more tips to help you raise your Monarchs so that they become beautiful butterflies.

Between egg and chrysalis the caterpillar or larva is going to shed its skin five times. When they are shedding their skin it is important not to disturb them. We suggest that you observe the life cycle but do not touch or interfere. Monarchs have been undergoing metamorphosis for hundreds of years and do not usually need our help.

If your larvae need more food we suggest you let them move themselves to the new plant. A potted plant can be placed next to an existing plant. Or, if the existing plant has no leaves, then prune it and put the stems you have cut off (with caterpillars) at the base of the new plant.

By the way, milkweed and Monarchs are poisonous so be careful when handling them. There is more information about this HERE. Monarch larvae store toxic steroids (known as cardenolides) from the milkweed they eat and use these cardenolides as a defence against predators such as birds. The bad taste and toxicity of both the larvae and adults are advertised by their warning colour. When a bird predator tastes a Monarch it learns to associate their colour and pattern with the bad taste and avoids preying on them in the future. (Interestingly, the Shining Cuckoo is not affected and will eat them.)

Be aware that there are different types of milkweed and the new plant(s) may not immediately appeal to your larvae. Water the plant well so that if there is an imbalance of cardenolides, they will be diluted.

If you are buying new plants as food for your caterpillars you should be careful about buying plants that have pesticide spray residue on them as this will affect and may even kill your brood. Ask your supplier if they are spray-free – or better yet have a go at planting next year’s in advance from seed. Seed is available on our website HERE.

Pesticides include fly sprays, plug-in insect controls and flea collars on pets so bear this in mind if you bring your larvae indoors.

If you are concerned that your caterpillars are dying, we suggest that you look in the forum HERE to see if there have been other similar reports – or add your own post. Don’t forget to add details like your locality, if the plants or new or well-established, number of caterpillars affected, if you have neighbours who spray and anything else you think is relevant.